Autozygome-guided exome sequencing in retinal dystrophy patients reveals pathogenetic mutations and novel candidate disease genes

Abstract

Retinal dystrophy (RD) is a heterogeneous group of hereditary diseases caused by loss of photoreceptor function and contributes significantly to the etiology of blindness globally but especially in the industrialized world. The extreme locus and allelic heterogeneity of these disorders poses a major diagnostic challenge and often impedes the ability to provide a molecular diagnosis that can inform counseling and gene-specific treatment strategies. In a large cohort of nearly 150 RD families, we used genomic approaches in the form of autozygome-guided mutation analysis and exome sequencing to identify the likely causative genetic lesion in the majority of cases. Additionally, our study revealed six novel candidate disease genes (C21orf2, EMC1, KIAA1549, GPR125, ACBD5, and DTHD1), two of which (ACBD5 and DTHD1) were observed in the context of syndromic forms of RD that are described for the first time.

Figure 1.

Workflow of the study.

Figure 2.

Central pie chart summarizes the contribution of various genes to the overall mutational pool among RD patients in the current study. Pie charts in the upper panel show the percentage of mutation-positive cases among simplex and multiplex cases using the autozygome-guided gene sequencing approach. Pie charts in the lower panel show the percentage of mutation-positive cases among simplex and multiplex cases using the exome sequencing approach. Please note the percentages in these charts do not take into account the novel candidate genes identified in this study.

Figure 3.

Western blot analysis of DTHD1 and ACBD5 in two families representing novel syndromic forms of RD. Fourfold reduction in the DTHD1 intensity in the patients compared to control and near-absence of the band corresponding to ACBD5 among patients can be seen. GAPDH is used for a loading control.