A novel variant of NEMF in a family with congenital fibrosis of the extraocular muscles: a case report and literature review

A novel variant of NEMF in a family with congenital fibrosis of the extraocular muscles: a case report and literature review | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report A novel variant of NEMF in a family with congenital fibrosis of the extraocular muscles: a case report and literature review Chuzhi Peng, Ranran Zhang, Hongyan Jia, Qinglin Chang, Dan Wang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4913975/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Congenital fibrosis of the extraocular muscles (CFEOM) is one of the congenital cranial dysinnervation disorders (CCDDs) characterized by hypoplastic oculomotor nerves (CN3), congenital ptosis and non-progressive restrictive ophthalmoplegia. The NEMF gene encodes a protein that resolves stalled ribosomes during translation. Variants in NEMF have been associated with neurodevelopmental and neuromuscular disorders, including intellectual disability, developmental delay, central nervous system impairment and peripheral neuropathy. Case presentation: We describe a family with CFEOM harboring a novel variant of NEMF gene. CFEOM3 was diagnosed in two siblings, a 9 year old girl and a 6 year old boy. Whole-exome sequencing (WES) revealed that the siblings carried a novel heterozygous NEMF variant c.1972A > C, p. (Lys658Gln). This variant was predicted to lead to the loss of hydrogen bonds, potentially affecting the spatial structure and stability of the NEMF protein. Conclusions Our findings support that the NEMF variant may be the cause of CFEOM in our case. This report expands the phenotypic spectrum of NEMF -associated diseases and provides a new candidate gene for CFEOM. Congenital fibrosis of the extraocular muscles NEMF heterozygous phenotypic spectrum Figures Figure 1 Figure 2 Background NEMF plays a critical role in the ribosome-associated quality control (RQC) pathway[ 1 ], which is essential for maintaining proteostasis and preventing neurodegeneration[ 2 , 3 ]. NEMF is highly expressed in the human brain. Variants in NEMF (OMIM#608378) can cause a range of neurodevelopmental disorders, such as intellectual disability (ID), developmental delay, central nervous system impairment and peripheral neuropathy[ 4 – 6 ]. Most reported cases are autosomal recessive inheritance. Patients with central nervous system impairment due to NEMF variants may exhibit abnormal eye movement phenotypes such as strabismus[ 6 ], but no association with congenital fibrosis of the extraocular muscles (CFEOM; HP:0001491) has been reported. CFEOM, as a class of congenital cranial dysinnervation disorders (CCDDs), is characterized by congenital ptosis and non-progressive restrictive ophthalmoplegia[ 7 ]. Hypoplasia of oculomotor nerves (CN3) is the most common MRI finding of CFEOM. CFEOM is mainly divided into three subtypes, CFEOM1, CFEOM2 and CFEOM3. CFEOM1 and CFEOM3 are autosomal dominant disorders, whereas CFEOM2 is an autosomal recessive disorder[ 8 ]. CFEOM1 presents with bilateral symmetrical ptosis and the eyes fixed in downgaze. CFEOM3 is a more variable eye phenotype that can include asymmetrical ptosis and oculomotility restrictions. CFEOM2 is typically characterized by bilateral restrictive ophthalmoplegia, pupil abnormalities, and ptosis. At present, several pathogenic genes are known to be related to CFEOM, including KIF21A, TUBB3, PHOX2A, TUBB2B and TUBA1A . Here, we report a novel NEMF missense variant associated with CFEOM in a family. This abnormal eye movement, which has not been previously reported, expands the phenotype spectrum of NEMF -related diseases. Case presentation The patients are children of non-consanguineous Chinese parents (Fig. 1 A), born at term with normal birth parameters. Both siblings reached the developmental milestones within the normal age range. No significant abnormalities were observed on their cranial MRI. The elder sister was a 9-year-old girl who presented to our ophthalmology clinic with abnormal eye movement since birth. She had already undergone right lateral rectus recession and medial rectus resection surgery at 4 years of age. On examination, she had right exotropia of 40 △ on modified Krimsky test and right ptosis. Ocular motility examination showed that she had − 3 limitation of abduction in the right eye. Her right eye moved into abduction on attempted adduction (Fig. 1 C). MRI of the brain and orbits revealed the hypoplasia of right CN3 (Fig. 1 E: e1) and bilateral abducens nerves (CN6) (Fig. 1 E: e2). In addition, her right medial rectus muscle (MR) appeared thinner (Fig. 1 E: e3). The younger brother was a six-year-old boy who was brought to our clinic with similar complaints as his older sister. At the time of presentation, he had undergone bilateral lateral rectus recession and medial rectus resection for exotropia and frontalis aponeurosis flap suspension for right ptosis. On examination, he was orthophoric in primary gaze with right ptosis and nystagmus. He presented with a compensatory left head turn. Ocular motility examination showed restricted horizontal movement and limitation in downgaze in his left eye. Additionally, he had upshoot of the right eye on attempted adduction (Fig. 1 D). MRI revealed the hypoplasia of bilateral CN3 (Fig. 1 F: f1), the absence of bilateral CN6 (Fig. 1 F: f2) and hypoplastic MR bilaterally (Fig. 1 F: f3-f4). Whole exome sequencing (WES) revealed that two siblings carried a novel heterozygous variant of NEMF (NM_004713: c.1972A > C, p. (Lys658Gln) (chr14: 50269389T>G, hg19)) and inherited from their unaffected father (Fig. 1 B). The heterozygous variant was validated by Sanger sequencing. According to the American College of Medical Genetics and Genomics (ACMG) genetic variant classification criteria and guidelines, the NEMF gene missense variant p. (Lys658Gln) was defined as a pathogenic variant (PVS1 + 2PM + 3PP). The variant resulted in a lysine to glutamine change at amino acid position 658 (Lys658Gln), which was not present in the Genome Aggregation Database (gnomAD), 1000 Genomes project, the Exome Aggregation Consortium (ExAC), or the NHLBI Exome Sequencing Project (ESP6500si). The conservation analysis based on the phyloP demonstrated that p. (Lys658Gln) substitution resulted in highly conserved amino acid changes, which was also analyzed in several common animals through the UGENE software (Fig. 2 B). A variety of bioinformatics prediction softwares, such as SIFT (deleterious), MutationTaster (disease causing), PolyPhen-2 (probably damaging) and LRT (deleterious), predicted the p. (Lys658Gln) substitution to be harmful. Protein-function prediction suggested that p. (Lys658Gln) substitution leads to a reduction in hydrogen bonds, affecting the stability of protein spatial structure (Fig. 2 C). We use the 3D protein structure of human NEMF predicted by AlphaFold (AF-O60524-F1) to conduct the computational-stability analysis. Multiple online servers indicated that the variant resulted in a decrease in the stability of the protein structure in terms of a significant decline in Gibbs free energy (Table 1 ). Table 1 The stability analysis of NEMF K658Q by different servers. Mutation I-Mutant 2.0 mCSM SDM DUET ENCoM DynaMut MAESTRO NEMF - K685Q ΔΔG (kcal/mol) -0.910 -0.996 -1.010 -0.940 -0.102 -0.333 0.058 Prediction Destabilizing Destabilizing Destabilizing Destabilizing Destabilizing Destabilizing Destabilizing Discussion and conclusions We report a family with CFEOM harboring a novel NEMF variant. Our patients present with unilateral ptosis and ophthalmoplegia of varying severity. MRI findings of hypoplastic CN3 and extraocular muscles in two siblings were consistent with CFEOM. CFEOM is a subset of CCDDs and belongs to the neurodevelopmental disorders. At present, the known pathogenic genes related to CFEOM include KIF21A , TUBB3 , PHOX2A , TUBB2B and TUBA1A . Among them, KIF21A and TUBB3 genes are the most common pathogenic genes, and variants of them have been reported to affect neurodevelopment and axon guidance[ 9 , 10 ]. Heterozygous missense variants in KIF21A and TUBB3 can cause CFEOM, while some variants also appear to exhibit incomplete penetrance. The NEMF gene has also been linked to neurodevelopmental diseases. The NEMF (Nuclear Export Mediator Factor) gene, located on chromosome 14q22, encodes a component of the RQC complex[ 11 ]. RQC ensures the quality of translation products by monitoring and eliminating incomplete nascent polypeptides produced from interrupted translation. RQC is a key molecular pathway that prevents neurodegeneration[ 6 , 12 ]. In a previous study, Anazi et al. reported NEMF as a new candidate gene for intellectual disability (ID)[ 4 ]. They identified homozygous truncating variants in two families with ID and developmental delay. Brain MRI of these patients showed no significant abnormalities. Next, Martin et al. described NEMF variants in seven families associated with juvenile neuromuscular disease, which presented with ID and motor neuron disease phenotypes of varying severities[ 5 ]. They proposed that NEMF was a novel gene associated with neurodegeneration and neuromuscular disease in mice and humans. In addition, Ahmed et al. found that NEMF may affect neuronal projection during early brain development, and that variants in NEMF can lead to central nervous system impairment and peripheral neuropathy[ 6 ]. Eye movement phenotypes have also been reported in NEMF -related diseases. In a previous study, a total of six cases with NEMF -related eye movement phenotypes were reported[ 6 ], including three cases of strabismus, one case of impaired smooth-pursuit and saccade eye movements, one case of impaired smooth-pursuit and saccade eye movements with esotropia, and one case of Duane syndrome Type 1. The patients in our study were diagnosed with CFEOM based on a combination with clinical findings and MRI findings. Our patients exhibited an atypical eye movement phenotype, characterized by abduction or upshoot of the right eye when attempting adduction. This CFEOM phenotype associated with a NEMF variant has not yet been reported. Most cases of human NEMF variants were reported to be associated with autosomal recessive inheritance. Martin et al. reported that a heterozygous variant in NEMF (c.1658T > C, p. (Ile553Thr)) caused later-onset peripheral neuropathy, including distal muscle atrophy and tremor[ 5 ]. Our patients carry a novel heterozygous variant in NEMF (c.1972A > C, p. (Lys658Gln)), which was inherited from their phenotypically unaffected father. Similarly, Senser et al. reported a member of a CFEOM family carrying a KIF21A variant who was clinically unaffected[ 13 ]. Additionally, Tischfield et al. discovered that a patient with CFEOM inherited the TUBB3 R62Q variant from his unaffected mother[ 10 ]. These observations suggest that the variants associated with CFEOM may exhibit incomplete penetrance. Homozygous Nemf mice displayed a series of neurologic phenotypes such as growth reduction, neurogenic muscle atrophy, and reduced lifespan, while findings of denervation of postsynaptic terminals and progressive axon loss in mice also supported the association between NEMF and neurodevelopmental abnormalities[ 5 ]; Knocking down Nemf gene in cultured mouse primary cortical neurons resulted in shorter axon length and fewer synapses[ 6 ]. Different mutation sites may lead to varying degrees of impact on NEMF function and differences in severity of symptoms. Martin et al. constructed two mouse models, where the R86S mutation located in the N-terminal domain resulted in a shorter lifespan and more severe phenotypes compared to the R487G mutation located in the second coiled-coil domain[ 5 ]. The variant p. (Lys658Gln) identified in this study is located in the R domain[ 14 ] (Fig. 2 A), and the substitution is predicted to reduce hydrogen bonds, affecting the structural stability of NEMF. In conclusion, this study reports a novel missense variant in NEMF causing CFEOM in two siblings. Additional research is needed to elucidate the impact of the missense variant on NEMF function. This study expands the clinical phenotypic spectrum of NEMF-related disorders and provides a new candidate pathogenic gene for CFEOM. Abbreviations CFEOM Congenital fibrosis of the extraocular muscles CCDDs Congenital cranial dysinnervation disorders CN3 Oculomotor nerves RQC Ribosome-associated quality control CN6 Abducens nerves MR Medial rectus muscle ID Intellectual disability Declarations Ethics approval and consent to participate This study was approved by the Institution Review Board of Beijing Tongren Hospital, Capital Medical University (TRECKY2018-035) and adhered to the ethical principles outlined in the Declaration of Helsinki. Consent for publication Written informed consent for publication of this case report was obtained from the parents. Competing interests The authors declare no competing interests. Funding This study was funded by the National Natural Science Foundation of China (No.82070999). Author Contribution CZ P designed the study, collected the data, reviewed the literature, analyzed the data, wrote the manuscript. RR Z analyzed the data, revised the manuscript. HY J analyzed the data, collected the data. QL C provided and analyzed the MRI results. D W collected the data. YH J designed the study, analyzed the data, supervised the study, revised the manuscript. All authors read and approved the final manuscript. Acknowledgement We are grateful to the patients and their family for their participation in the study. Data availability All data generated or analyzed in this study are presented in this article. References Brandman O, Hegde RS. Ribosome-associated protein quality control. Nat Struct Mol Biol. 2016;23(1):7–15. Defenouillere Q, Fromont-Racine M. The ribosome-bound quality control complex: from aberrant peptide clearance to proteostasis maintenance. Curr Genet. 2017;63(6):997–1005. Lu B. Translational regulation by ribosome-associated quality control in neurodegenerative disease, cancer, and viral infection. Front Cell Dev Biol. 2022;10:970654. Anazi S, Maddirevula S, Faqeih E, Alsedairy H, Alzahrani F, Shamseldin HE, Patel N, Hashem M, Ibrahim N, Abdulwahab F, et al. Clinical genomics expands the morbid genome of intellectual disability and offers a high diagnostic yield. Mol Psychiatry. 2017;22(4):615–24. Martin PB, Kigoshi-Tansho Y, Sher RB, Ravenscroft G, Stauffer JE, Kumar R, Yonashiro R, Muller T, Griffith C, Allen W, et al. NEMF mutations that impair ribosome-associated quality control are associated with neuromuscular disease. Nat Commun. 2020;11(1):4625. Ahmed A, Wang M, Bergant G, Maroofian R, Zhao R, Alfadhel M, Nashabat M, AlRifai MT, Eyaid W, Alswaid A, et al. Biallelic loss-of-function variants in NEMF cause central nervous system impairment and axonal polyneuropathy. Hum Genet. 2021;140(4):579–92. Heidary G, Engle EC, Hunter DG. Congenital fibrosis of the extraocular muscles. Semin Ophthalmol. 2008;23(1):3–8. Whitman MC, Engle EC. Ocular congenital cranial dysinnervation disorders (CCDDs): insights into axon growth and guidance. Hum Mol Genet. 2017;26(R1):R37–44. Cheng L, Desai J, Miranda CJ, Duncan JS, Qiu W, Nugent AA, Kolpak AL, Wu CC, Drokhlyansky E, Delisle MM, et al. Human CFEOM1 mutations attenuate KIF21A autoinhibition and cause oculomotor axon stalling. Neuron. 2014;82(2):334–49. Tischfield MA, Baris HN, Wu C, Rudolph G, Van Maldergem L, He W, Chan WM, Andrews C, Demer JL, Robertson RL, et al. Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance. Cell. 2010;140(1):74–87. Shao S, Brown A, Santhanam B, Hegde RS. Structure and assembly pathway of the ribosome quality control complex. Mol Cell. 2015;57(3):433–44. Udagawa T, Seki M, Okuyama T, Adachi S, Natsume T, Noguchi T, Matsuzawa A, Inada T. Failure to Degrade CAT-Tailed Proteins Disrupts Neuronal Morphogenesis and Cell Survival. Cell Rep. 2021;34(1):108599. Sener EC, Lee BA, Turgut B, Akarsu AN, Engle EC. A clinically variant fibrosis syndrome in a Turkish family maps to the CFEOM1 locus on chromosome 12. Arch Ophthalmol. 2000;118(8):1090–7. Lytvynenko I, Paternoga H, Thrun A, Balke A, Muller TA, Chiang CH, Nagler K, Tsaprailis G, Anders S, Bischofs I, et al. Alanine Tails Signal Proteolysis in Bacterial Ribosome-Associated Quality Control. Cell. 2019;178(1):76–e9022. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4913975","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":350314779,"identity":"6c7f590e-1135-4866-b983-d35480b7c9ee","order_by":0,"name":"Chuzhi Peng","email":"","orcid":"","institution":"Beijing Tongren Eye Center, Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Chuzhi","middleName":"","lastName":"Peng","suffix":""},{"id":350314780,"identity":"de1e1788-3e6c-426d-8479-ce3fced44762","order_by":1,"name":"Ranran Zhang","email":"","orcid":"","institution":"Beijing Tongren Eye Center, Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Ranran","middleName":"","lastName":"Zhang","suffix":""},{"id":350314781,"identity":"a2c58f9a-6eb8-446a-b152-4e5903836871","order_by":2,"name":"Hongyan Jia","email":"","orcid":"","institution":"Beijing Tongren Eye Center, Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Hongyan","middleName":"","lastName":"Jia","suffix":""},{"id":350314782,"identity":"e9ad76a5-c3aa-45c3-aff8-62b40fa70c7b","order_by":3,"name":"Qinglin Chang","email":"","orcid":"","institution":"Beijing Tongren Hospital","correspondingAuthor":false,"prefix":"","firstName":"Qinglin","middleName":"","lastName":"Chang","suffix":""},{"id":350314783,"identity":"f5747680-ff96-44cd-aed6-ffe2f6da9ed8","order_by":4,"name":"Dan Wang","email":"","orcid":"","institution":"Beijing Tongren Eye Center, Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Dan","middleName":"","lastName":"Wang","suffix":""},{"id":350314784,"identity":"ca5350d7-0ba9-4a8b-8edb-cc93a0dd3408","order_by":5,"name":"Yonghong Jiao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5UlEQVRIie3Pv4vCMBTA8QeBuKR2bfHnnxAIyIH3x7wi6OLg6CSFQqcD/5WAg9yWksGlf0DhHKxdHXRzULyLk1ObUbh8twfvw0sAXK53LABUAJ+MEqLgwO3JtO+3KAJaEpMW4ZpxQBvBf+JSXZckkppdzrjQ0RZIeSzqyF5h9pXTP+JtAuQ6+o6pEPM6UiAqL2WGyCeRitFOE8nuaWAeVl2tifZSLsKEUbsroSHdHPs+oaMP5DMhdcNf2sV8cjktH4z6uirOt3FP7pKyqiNDxfB1TgBIzbppELfU67xq2He5XK7/2C+7qVeqUaH4PQAAAABJRU5ErkJggg==","orcid":"","institution":"Beijing Tongren Eye Center, Capital Medical University","correspondingAuthor":true,"prefix":"","firstName":"Yonghong","middleName":"","lastName":"Jiao","suffix":""}],"badges":[],"createdAt":"2024-08-14 13:27:34","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4913975/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4913975/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":64623663,"identity":"702b3f3d-9be5-470a-ae0e-9eacf1f3c362","added_by":"auto","created_at":"2024-09-16 17:04:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":669503,"visible":true,"origin":"","legend":"\u003cp\u003eThe clinical features and MRI findings of the two siblings with a \u003cem\u003eNEMF\u003c/em\u003evariant. \u003cstrong\u003eA\u003c/strong\u003e The family tree of the CFEOM family harboring a \u003cem\u003eNEMF\u003c/em\u003evariant. \u003cstrong\u003eB\u003c/strong\u003e Sequencing chromatogram of heterozygous variant c.1972A \u0026gt;C(arrow) in \u003cem\u003eNEMF\u003c/em\u003e. \u003cstrong\u003eC-D\u003c/strong\u003e Diagnostic positions of the gaze of the elder sister (C) and her young brother (D). \u003cstrong\u003eE\u003c/strong\u003e MRI findings of the elder sister. Hypoplasia of right CN3(e1) and bilateral CN6(e2), and thinner right MR(e3). \u003cstrong\u003eF\u003c/strong\u003e MRI findings of the younger brother. Hypoplasia of bilateral CN3(f1), absence of CN6(f2), and atrophy of bilateral MR (f3, f4).\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4913975/v1/f283df5ef673e9c29a788cee.png"},{"id":64623033,"identity":"57488608-ddf9-4461-a94b-0bc0d79ca0c1","added_by":"auto","created_at":"2024-09-16 16:56:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":337705,"visible":true,"origin":"","legend":"\u003cp\u003eThe \u003cem\u003eNEMF\u003c/em\u003e variant analysis. \u003cstrong\u003eA\u003c/strong\u003e Predicted NEMF protein structure: NFACT-N(N), helix-hairpin-helix (HhH), coiled-coil (cc), middle domain (M), NFACT-R (R), and NFACT-C (C). The novel variant c.1972A \u0026gt;C(red) and previously reported variants(black) are indicated. \u003cstrong\u003eB\u003c/strong\u003e The NEMF protein sequence alignment among nine different species demonstrates the evolutionary conservation of residue K658. \u003cstrong\u003eC\u003c/strong\u003e Changes of amino acid interaction force before and after the p. (Lys658Gln) substitution. RefSeq of \u003cem\u003eNEMF\u003c/em\u003e: NM_004713.6.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-4913975/v1/444fc58700d8e0ec2f4d5247.png"},{"id":64624029,"identity":"4f524230-684d-4e4f-8a07-546f092e916c","added_by":"auto","created_at":"2024-09-16 17:12:25","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1500132,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4913975/v1/3190c719-e217-4203-bf82-6d246650f140.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"A novel variant of NEMF in a family with congenital fibrosis of the extraocular muscles: a case report and literature review","fulltext":[{"header":"Background","content":"\u003cp\u003eNEMF plays a critical role in the ribosome-associated quality control (RQC) pathway[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], which is essential for maintaining proteostasis and preventing neurodegeneration[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. NEMF is highly expressed in the human brain. Variants in \u003cem\u003eNEMF\u003c/em\u003e(OMIM#608378) can cause a range of neurodevelopmental disorders, such as intellectual disability (ID), developmental delay, central nervous system impairment and peripheral neuropathy[\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Most reported cases are autosomal recessive inheritance. Patients with central nervous system impairment due to \u003cem\u003eNEMF\u003c/em\u003e variants may exhibit abnormal eye movement phenotypes such as strabismus[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], but no association with congenital fibrosis of the extraocular muscles (CFEOM; HP:0001491) has been reported.\u003c/p\u003e \u003cp\u003eCFEOM, as a class of congenital cranial dysinnervation disorders (CCDDs), is characterized by congenital ptosis and non-progressive restrictive ophthalmoplegia[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Hypoplasia of oculomotor nerves (CN3) is the most common MRI finding of CFEOM. CFEOM is mainly divided into three subtypes, CFEOM1, CFEOM2 and CFEOM3. CFEOM1 and CFEOM3 are autosomal dominant disorders, whereas CFEOM2 is an autosomal recessive disorder[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. CFEOM1 presents with bilateral symmetrical ptosis and the eyes fixed in downgaze. CFEOM3 is a more variable eye phenotype that can include asymmetrical ptosis and oculomotility restrictions. CFEOM2 is typically characterized by bilateral restrictive ophthalmoplegia, pupil abnormalities, and ptosis. At present, several pathogenic genes are known to be related to CFEOM, including \u003cem\u003eKIF21A, TUBB3, PHOX2A, TUBB2B\u003c/em\u003e and \u003cem\u003eTUBA1A\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eHere, we report a novel \u003cem\u003eNEMF\u003c/em\u003e missense variant associated with CFEOM in a family. This abnormal eye movement, which has not been previously reported, expands the phenotype spectrum of \u003cem\u003eNEMF\u003c/em\u003e-related diseases.\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cp\u003eThe patients are children of non-consanguineous Chinese parents (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA), born at term with normal birth parameters. Both siblings reached the developmental milestones within the normal age range. No significant abnormalities were observed on their cranial MRI.\u003c/p\u003e \u003cp\u003eThe elder sister was a 9-year-old girl who presented to our ophthalmology clinic with abnormal eye movement since birth. She had already undergone right lateral rectus recession and medial rectus resection surgery at 4 years of age. On examination, she had right exotropia of 40\u003csup\u003e△\u003c/sup\u003e on modified Krimsky test and right ptosis. Ocular motility examination showed that she had \u0026minus;\u0026thinsp;3 limitation of abduction in the right eye. Her right eye moved into abduction on attempted adduction (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC). MRI of the brain and orbits revealed the hypoplasia of right CN3 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eE: e1) and bilateral abducens nerves (CN6) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eE: e2). In addition, her right medial rectus muscle (MR) appeared thinner (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eE: e3).\u003c/p\u003e \u003cp\u003eThe younger brother was a six-year-old boy who was brought to our clinic with similar complaints as his older sister. At the time of presentation, he had undergone bilateral lateral rectus recession and medial rectus resection for exotropia and frontalis aponeurosis flap suspension for right ptosis. On examination, he was orthophoric in primary gaze with right ptosis and nystagmus. He presented with a compensatory left head turn. Ocular motility examination showed restricted horizontal movement and limitation in downgaze in his left eye. Additionally, he had upshoot of the right eye on attempted adduction (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD). MRI revealed the hypoplasia of bilateral CN3 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eF: f1), the absence of bilateral CN6 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eF: f2) and hypoplastic MR bilaterally (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eF: f3-f4).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhole exome sequencing (WES) revealed that two siblings carried a novel heterozygous variant of \u003cem\u003eNEMF\u003c/em\u003e (NM_004713: c.1972A\u0026thinsp;\u0026gt;\u0026thinsp;C, p. (Lys658Gln) (chr14: 50269389T\u0026gt;G, hg19)) and inherited from their unaffected father (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). The heterozygous variant was validated by Sanger sequencing. According to the American College of Medical Genetics and Genomics (ACMG) genetic variant classification criteria and guidelines, the \u003cem\u003eNEMF\u003c/em\u003e gene missense variant p. (Lys658Gln) was defined as a pathogenic variant (PVS1\u0026thinsp;+\u0026thinsp;2PM\u0026thinsp;+\u0026thinsp;3PP). The variant resulted in a lysine to glutamine change at amino acid position 658 (Lys658Gln), which was not present in the Genome Aggregation Database (gnomAD), 1000 Genomes project, the Exome Aggregation Consortium (ExAC), or the NHLBI Exome Sequencing Project (ESP6500si). The conservation analysis based on the phyloP demonstrated that p. (Lys658Gln) substitution resulted in highly conserved amino acid changes, which was also analyzed in several common animals through the UGENE software (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). A variety of bioinformatics prediction softwares, such as SIFT (deleterious), MutationTaster (disease causing), PolyPhen-2 (probably damaging) and LRT (deleterious), predicted the p. (Lys658Gln) substitution to be harmful. Protein-function prediction suggested that p. (Lys658Gln) substitution leads to a reduction in hydrogen bonds, affecting the stability of protein spatial structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC). We use the 3D protein structure of human NEMF predicted by AlphaFold (AF-O60524-F1) to conduct the computational-stability analysis. Multiple online servers indicated that the variant resulted in a decrease in the stability of the protein structure in terms of a significant decline in Gibbs free energy (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe stability analysis of \u003cem\u003eNEMF\u003c/em\u003e K658Q by different servers.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMutation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI-Mutant 2.0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003emCSM\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSDM\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eDUET\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eENCoM\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eDynaMut\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMAESTRO\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eNEMF\u003c/em\u003e-\u003c/p\u003e \u003cp\u003eK685Q\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eΔΔG\u003c/p\u003e \u003cp\u003e(kcal/mol)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.910\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.996\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-1.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.940\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-0.333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.058\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePrediction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDestabilizing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDestabilizing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDestabilizing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eDestabilizing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eDestabilizing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eDestabilizing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eDestabilizing\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion and conclusions","content":"\u003cp\u003eWe report a family with CFEOM harboring a novel \u003cem\u003eNEMF\u003c/em\u003e variant. Our patients present with unilateral ptosis and ophthalmoplegia of varying severity. MRI findings of hypoplastic CN3 and extraocular muscles in two siblings were consistent with CFEOM. CFEOM is a subset of CCDDs and belongs to the neurodevelopmental disorders. At present, the known pathogenic genes related to CFEOM include \u003cem\u003eKIF21A\u003c/em\u003e, \u003cem\u003eTUBB3\u003c/em\u003e, \u003cem\u003ePHOX2A\u003c/em\u003e, \u003cem\u003eTUBB2B\u003c/em\u003e and \u003cem\u003eTUBA1A\u003c/em\u003e. Among them, \u003cem\u003eKIF21A\u003c/em\u003e and \u003cem\u003eTUBB3\u003c/em\u003e genes are the most common pathogenic genes, and variants of them have been reported to affect neurodevelopment and axon guidance[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Heterozygous missense variants in \u003cem\u003eKIF21A\u003c/em\u003e and \u003cem\u003eTUBB3\u003c/em\u003e can cause CFEOM, while some variants also appear to exhibit incomplete penetrance.\u003c/p\u003e \u003cp\u003eThe \u003cem\u003eNEMF\u003c/em\u003e gene has also been linked to neurodevelopmental diseases. The \u003cem\u003eNEMF\u003c/em\u003e (Nuclear Export Mediator Factor) gene, located on chromosome 14q22, encodes a component of the RQC complex[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. RQC ensures the quality of translation products by monitoring and eliminating incomplete nascent polypeptides produced from interrupted translation. RQC is a key molecular pathway that prevents neurodegeneration[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In a previous study, Anazi et al. reported \u003cem\u003eNEMF\u003c/em\u003e as a new candidate gene for intellectual disability (ID)[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. They identified homozygous truncating variants in two families with ID and developmental delay. Brain MRI of these patients showed no significant abnormalities. Next, Martin et al. described \u003cem\u003eNEMF\u003c/em\u003e variants in seven families associated with juvenile neuromuscular disease, which presented with ID and motor neuron disease phenotypes of varying severities[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. They proposed that \u003cem\u003eNEMF\u003c/em\u003e was a novel gene associated with neurodegeneration and neuromuscular disease in mice and humans. In addition, Ahmed et al. found that NEMF may affect neuronal projection during early brain development, and that variants in \u003cem\u003eNEMF\u003c/em\u003e can lead to central nervous system impairment and peripheral neuropathy[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eEye movement phenotypes have also been reported in \u003cem\u003eNEMF\u003c/em\u003e-related diseases. In a previous study, a total of six cases with \u003cem\u003eNEMF\u003c/em\u003e-related eye movement phenotypes were reported[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], including three cases of strabismus, one case of impaired smooth-pursuit and saccade eye movements, one case of impaired smooth-pursuit and saccade eye movements with esotropia, and one case of Duane syndrome Type 1. The patients in our study were diagnosed with CFEOM based on a combination with clinical findings and MRI findings. Our patients exhibited an atypical eye movement phenotype, characterized by abduction or upshoot of the right eye when attempting adduction. This CFEOM phenotype associated with a \u003cem\u003eNEMF\u003c/em\u003e variant has not yet been reported.\u003c/p\u003e \u003cp\u003eMost cases of human \u003cem\u003eNEMF\u003c/em\u003e variants were reported to be associated with autosomal recessive inheritance. Martin et al. reported that a heterozygous variant in \u003cem\u003eNEMF\u003c/em\u003e (c.1658T\u0026thinsp;\u0026gt;\u0026thinsp;C, p. (Ile553Thr)) caused later-onset peripheral neuropathy, including distal muscle atrophy and tremor[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Our patients carry a novel heterozygous variant in \u003cem\u003eNEMF\u003c/em\u003e (c.1972A\u0026thinsp;\u0026gt;\u0026thinsp;C, p. (Lys658Gln)), which was inherited from their phenotypically unaffected father. Similarly, Senser et al. reported a member of a CFEOM family carrying a \u003cem\u003eKIF21A\u003c/em\u003e variant who was clinically unaffected[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Additionally, Tischfield et al. discovered that a patient with CFEOM inherited the TUBB3 R62Q variant from his unaffected mother[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. These observations suggest that the variants associated with CFEOM may exhibit incomplete penetrance.\u003c/p\u003e \u003cp\u003eHomozygous \u003cem\u003eNemf\u003c/em\u003e mice displayed a series of neurologic phenotypes such as growth reduction, neurogenic muscle atrophy, and reduced lifespan, while findings of denervation of postsynaptic terminals and progressive axon loss in mice also supported the association between \u003cem\u003eNEMF\u003c/em\u003e and neurodevelopmental abnormalities[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]; Knocking down \u003cem\u003eNemf\u003c/em\u003e gene in cultured mouse primary cortical neurons resulted in shorter axon length and fewer synapses[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Different mutation sites may lead to varying degrees of impact on NEMF function and differences in severity of symptoms. Martin et al. constructed two mouse models, where the R86S mutation located in the N-terminal domain resulted in a shorter lifespan and more severe phenotypes compared to the R487G mutation located in the second coiled-coil domain[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The variant p. (Lys658Gln) identified in this study is located in the R domain[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA), and the substitution is predicted to reduce hydrogen bonds, affecting the structural stability of NEMF.\u003c/p\u003e \u003cp\u003eIn conclusion, this study reports a novel missense variant in \u003cem\u003eNEMF\u003c/em\u003e causing CFEOM in two siblings. Additional research is needed to elucidate the impact of the missense variant on NEMF function. This study expands the clinical phenotypic spectrum of NEMF-related disorders and provides a new candidate pathogenic gene for CFEOM.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCFEOM Congenital fibrosis of the extraocular muscles\u003c/p\u003e\u003cp\u003eCCDDs Congenital cranial dysinnervation disorders\u003c/p\u003e\u003cp\u003eCN3 Oculomotor nerves\u003c/p\u003e\u003cp\u003eRQC Ribosome-associated quality control\u003c/p\u003e\u003cp\u003eCN6 Abducens nerves\u003c/p\u003e\u003cp\u003eMR Medial rectus muscle\u003c/p\u003e\u003cp\u003eID Intellectual disability\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eEthics approval and consent to participate\u003c/h2\u003e\n\u003cp\u003eThis study was approved by the Institution Review Board of Beijing Tongren Hospital, Capital Medical University (TRECKY2018-035) and adhered to the ethical principles outlined in the Declaration of Helsinki.\u003c/p\u003e\n\u003ch2\u003eConsent for publication\u003c/h2\u003e\n\u003cp\u003eWritten informed consent for publication of this case report was obtained from the parents.\u003c/p\u003e\n\u003ch2\u003eCompeting interests\u003c/h2\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThis study was funded by the National Natural Science Foundation of China (No.82070999).\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eCZ P designed the study, collected the data, reviewed the literature, analyzed the data, wrote the manuscript. RR Z analyzed the data, revised the manuscript. HY J analyzed the data, collected the data. QL C provided and analyzed the MRI results. D W collected the data. YH J designed the study, analyzed the data, supervised the study, revised the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eWe are grateful to the patients and their family for their participation in the study.\u003c/p\u003e\n\u003ch2\u003eData availability\u003c/h2\u003e\n\u003cp\u003eAll data generated or analyzed in this study are presented in this article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBrandman O, Hegde RS. Ribosome-associated protein quality control. Nat Struct Mol Biol. 2016;23(1):7\u0026ndash;15.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDefenouillere Q, Fromont-Racine M. The ribosome-bound quality control complex: from aberrant peptide clearance to proteostasis maintenance. Curr Genet. 2017;63(6):997\u0026ndash;1005.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLu B. Translational regulation by ribosome-associated quality control in neurodegenerative disease, cancer, and viral infection. Front Cell Dev Biol. 2022;10:970654.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnazi S, Maddirevula S, Faqeih E, Alsedairy H, Alzahrani F, Shamseldin HE, Patel N, Hashem M, Ibrahim N, Abdulwahab F, et al. Clinical genomics expands the morbid genome of intellectual disability and offers a high diagnostic yield. Mol Psychiatry. 2017;22(4):615\u0026ndash;24.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMartin PB, Kigoshi-Tansho Y, Sher RB, Ravenscroft G, Stauffer JE, Kumar R, Yonashiro R, Muller T, Griffith C, Allen W, et al. NEMF mutations that impair ribosome-associated quality control are associated with neuromuscular disease. Nat Commun. 2020;11(1):4625.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAhmed A, Wang M, Bergant G, Maroofian R, Zhao R, Alfadhel M, Nashabat M, AlRifai MT, Eyaid W, Alswaid A, et al. Biallelic loss-of-function variants in NEMF cause central nervous system impairment and axonal polyneuropathy. Hum Genet. 2021;140(4):579\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHeidary G, Engle EC, Hunter DG. Congenital fibrosis of the extraocular muscles. Semin Ophthalmol. 2008;23(1):3\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWhitman MC, Engle EC. Ocular congenital cranial dysinnervation disorders (CCDDs): insights into axon growth and guidance. Hum Mol Genet. 2017;26(R1):R37\u0026ndash;44.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheng L, Desai J, Miranda CJ, Duncan JS, Qiu W, Nugent AA, Kolpak AL, Wu CC, Drokhlyansky E, Delisle MM, et al. Human CFEOM1 mutations attenuate KIF21A autoinhibition and cause oculomotor axon stalling. Neuron. 2014;82(2):334\u0026ndash;49.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTischfield MA, Baris HN, Wu C, Rudolph G, Van Maldergem L, He W, Chan WM, Andrews C, Demer JL, Robertson RL, et al. Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance. Cell. 2010;140(1):74\u0026ndash;87.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShao S, Brown A, Santhanam B, Hegde RS. Structure and assembly pathway of the ribosome quality control complex. Mol Cell. 2015;57(3):433\u0026ndash;44.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUdagawa T, Seki M, Okuyama T, Adachi S, Natsume T, Noguchi T, Matsuzawa A, Inada T. Failure to Degrade CAT-Tailed Proteins Disrupts Neuronal Morphogenesis and Cell Survival. Cell Rep. 2021;34(1):108599.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSener EC, Lee BA, Turgut B, Akarsu AN, Engle EC. A clinically variant fibrosis syndrome in a Turkish family maps to the CFEOM1 locus on chromosome 12. Arch Ophthalmol. 2000;118(8):1090\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLytvynenko I, Paternoga H, Thrun A, Balke A, Muller TA, Chiang CH, Nagler K, Tsaprailis G, Anders S, Bischofs I, et al. Alanine Tails Signal Proteolysis in Bacterial Ribosome-Associated Quality Control. Cell. 2019;178(1):76\u0026ndash;e9022.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Congenital fibrosis of the extraocular muscles, NEMF, heterozygous, phenotypic spectrum","lastPublishedDoi":"10.21203/rs.3.rs-4913975/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4913975/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eCongenital fibrosis of the extraocular muscles (CFEOM) is one of the congenital cranial dysinnervation disorders (CCDDs) characterized by hypoplastic oculomotor nerves (CN3), congenital ptosis and non-progressive restrictive ophthalmoplegia. The \u003cem\u003eNEMF\u003c/em\u003e gene encodes a protein that resolves stalled ribosomes during translation. Variants in \u003cem\u003eNEMF\u003c/em\u003e have been associated with neurodevelopmental and neuromuscular disorders, including intellectual disability, developmental delay, central nervous system impairment and peripheral neuropathy.\u003c/p\u003e\u003ch2\u003eCase presentation:\u003c/h2\u003e \u003cp\u003eWe describe a family with CFEOM harboring a novel variant of \u003cem\u003eNEMF\u003c/em\u003e gene. CFEOM3 was diagnosed in two siblings, a 9 year old girl and a 6 year old boy. Whole-exome sequencing (WES) revealed that the siblings carried a novel heterozygous \u003cem\u003eNEMF\u003c/em\u003e variant c.1972A\u0026thinsp;\u0026gt;\u0026thinsp;C, p. (Lys658Gln). This variant was predicted to lead to the loss of hydrogen bonds, potentially affecting the spatial structure and stability of the NEMF protein.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eOur findings support that the \u003cem\u003eNEMF\u003c/em\u003e variant may be the cause of CFEOM in our case. This report expands the phenotypic spectrum of \u003cem\u003eNEMF\u003c/em\u003e-associated diseases and provides a new candidate gene for CFEOM.\u003c/p\u003e","manuscriptTitle":"A novel variant of NEMF in a family with congenital fibrosis of the extraocular muscles: a case report and literature review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-09-16 16:56:17","doi":"10.21203/rs.3.rs-4913975/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3099fcfc-12da-4353-b071-4f2c21d0ff44","owner":[],"postedDate":"September 16th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-09-16T16:56:20+00:00","versionOfRecord":[],"versionCreatedAt":"2024-09-16 16:56:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4913975","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4913975","identity":"rs-4913975","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}