Abstract
Background
Familial exudative vitreoretinopathy (FEVR) is a clinically and genetically heterogeneous ophthalmic disease that is characterized by incomplete retinal vascular development. NDP gene is the main cause reason of X-linked FEVR.
Methods
Copy Number Variation Sequencing, chromosomal microarray, Whole exome sequencing and Sanger sequencing were performed to find and confirm the candidate variant. The functional effect of the candidate variant was further investigated in HEK293 and HeLa cells with pcMINI and pcMINI-N vectors by minigene splicing assay in vitro. Summary of known pathogenic variants in the 5′-untranslated regions (5’UTR) of the NDP gene and their clinical characteristics.
Results
Whole exome sequencing identified a novel hemizygous 5' UTR variant (NM_000266.4: c.-167_-166delinsAAGG) in the NDP gene. Sanger sequencing confirmed this variant was co-segregated with FEVR in the family. Minigene splicing assay verified that this variant leaded to part of deletions in exon 2. Pathogenic variations in the 5’UTR were distributed in three types: 1. indels in dipyrimidine repeats (exon1); 2. variants in splice region (intron 1); 3. variants in exon2 (5'UTR). Most patients (5/8) with variations in dipyrimidine repeats region were diagnosed with ROP, while Patients (4/6) with splice-site variants in intron 1 were mainly diagnosed with ND and all patients (7/7) with variations in exon2 (5'UTR region) were diagnosed with FEVR.
Conclusions
Our study identified a likely pathogenic variant in 5'UTR of NDP gene and validated it affected splicing of NDP. Our analysis also found the correlation between the location of the variations in 5'UTR and disease, provided assistance in prognosis of disease.