Morphological, behavioral and molecular studies on CRISPR/Cas9-mediated knockout of the NOMO1 gene in zebrafish

Abstract Background: Multiple clinical genome-wide analysis identified that chromosome 16p13.11 is a hotspot associated with neuropsychiatric disorders such as autism, schizophrenia and epilepsy. Nodal modulator 1 (NOMO1), located on human chromosome 16p13.11, was considered as a candidate gene with neuropsychiatric disorders. However, it is unknown whether the nomo1 deficiency causes neurological abnormalities, and the molecular mechanisms and pathogenesis of the NOMO1 gene remain unclear. To study the effects of nomo1 deficiency on brain development and neuropsychiatric system, a nomo1 knockout zebrafish model was established.Methods: We developed a viable vertebrate model of nomo1 loss-of-function using CRISPR/Cas9 technology and characterized nomo1 mutant zebrafish. Phenotypic and functional studies of developing nomo1 mutant zebrafish, including morphological measurements, behavioral assays, and functional mechanistic analyses, were performed.Results: Morphological differences in the phenotype of nomo1-/- zebrafish gradually became less noticeable during development, however, the enlarged interstitial spaces in midbrain and hindbrain were detected in nomo1 mutant zebrafish. Meanwhile, the nomo1 deficiency caused the change of expression levels in neurotransmitters of γ-aminobutyrate, glutamate and serotonin. Interestingly, the nomo1 loss-of-function zebrafish model exhibited social defects and repetitive behaviors in juvenile, which represented autism-like behaviors. The transcriptome analysis showed different gene expression patterns in mutant zebrafish at the genetic level. Further results revealed that the neuroactive drug PTZ recovered the decreased locomotor phenotype in larval mutant zebrafish.Conclusions: In this study, we established a nomo1 vertebrate animal model using CRISPR/Cas9 gene editing approach. The loss-of-function of nomo1 displayed autism-like behaviors and altered levels of the γ-aminobutyrate, glutamate and serotonin in zebrafish, which provide evidence that nomo1 as a candidate gene for autism. The versatility of zebrafish model is contributed to studying NOMO1-related disorders and conducting drug screening in future.Limitations: Further studies are needed to determine whether an intervention with a neuroactive drug in nomo1-/- zebrafish to alter the behavioral phenotype is applicable to the behavior of human patients.