Two novel mutations in TTC21B gene, c.497del and c.2323-3T>A, identified in a Chinese patient

Methods: A whole-exome sequencing end stage renal disease patient whose original renal disease is unknown. Swiss model predict the 3D structure of the protein. The related literature was searched by using search terms “NPHP” in PubMed CNKI and VIP database from January 2000 to January 2020. Results The whole exome by next-generation sequencing and found two unreported TTC21B mutation sites, c.497del (p.Lys166Serfs) and c.2323−3T > A. The c.497del (p.Lys166Serfs) variant, which is a frame shift mutation, suggested deletion of a single nucleotide. A at position 497 from the TTC21B gene CDS results in replacement of lysine by serine at codon 166 of the TTC21B protein, as well as premature translational stop at position 201. The c.2323−3T > A variant indicates that the antepenultimate base of intron upstream of nucleotide 2323 in the CDS region of TTC21B gene changes from T to A. The change in the three-dimensional structure of the protein caused by the mutations in TTC21B may affect the functions associated with the protein length shorten. Further, this study summarized 25 NPHP gene mutations and the phenotypes that have been reported. Conclusion This study reported two novel mutations in the TTC21B gene resulting in NPHP in a Chinese patient and expanded on the spectrum of known causative mutations of TTC21B gene.