Whole-exome sequencing identified genes known to be responsible for retinitis pigmentosa in 28 Chinese families

Abstract

Purpose: Retinitis pigmentosa (RP) is a group of highly heterogenetic inherited retinal degeneration diseases. Molecular genetic diagnosis of RP is quite challenging because of the complicated disease-causing mutation spectrum. The aim of this study was to explore the mutation spectrum in Chinese RP patients using next-generation sequencing technology and to explore the genotype-phenotype relationship.

Method: In this study, a cost-effective strategy using whole-exome sequencing (WES) was employed to address the genetic diagnosis of 28 RP families in China. One to two patients and zero to two healthy relatives were sequenced in each family. All mutations in WES data that passed through the filtering procedure were searched in relation to 662 gene defects that can cause vision-associated phenotypes (including 89 RP genes in the RetNet Database). All patients visiting the outpatient department received comprehensive ophthalmic examinations.

Result: Twenty-five putative pathogenic mutations of 12 genes were detected by WES and were all confirmed by Sanger sequencing in 20 (20/28, 71.4%) families, including the 12 following genes: USH2A, CYP4V2, PRPF31, RHO, RP1, CNGA1, CNGB1, EYS, PRPF3, RP2, RPGR, and TOPORS. Three families were rediagnosed as having Bietti crystalline dystrophy (BCD). USH2A (4/20, 20%) and CYP4V2 (3/20, 15%) were found to be the most frequent mutated genes. Seven novel mutations were identified in this research, including mutations in USH2A1, USH2A2, PRPF31, RP2, TOPORS, CNGB1, and RPGR. Phenotype and genotype relationships in the 12 RP genes were analyzed, which revealed later disease onset and more severe visual function defects in CYP4V2.

Conclusion: Twenty-five putative pathogenic mutations of 12 genes were detected by WES, and these were all confirmed by Sanger sequencing in 20 (20/28, 71.4%) families, including seven novel mutations. USH2A and CYP4V2 were found to be the most frequent genes in this research. Phenotype and genotype relationships were revealed, and the mutation spectrum of RP in Chinese populations was expanded in this research, which may benefit future cutting-edge therapies.

Figure 1

Pedigree charts of the 20 retinitis pigmentosa (RP) families with confirmed molecular diagnosis. The genotype of each individual sequenced is mentioned in bold, and individuals who were clinically investigated in our outpatient department are indicated with black frames.

Figure 2

Phenotype–genotype relationship. Bars represent average disease duration of each gene; blue line and annotated data aside represent average visual acuity of individuals in each gene; black dots represent average disease onset in each gene.

Figure 3

Fundus images of patients with USH2A mutations.

Figure 4

Fundus images of patients with CYP4V2 mutations and typical acentric visual field from patient RP026 II:3.

Figure 5

Fundus images of patients with novel mutations in PRPF31, RP2, TOPORS, CNGB1, and RPGR.