Comprehensive Molecular Diagnosis of a Large Chinese Leber Congenital Amaurosis Cohort

Abstract

Purpose: Leber congenital amaurosis (LCA) is an inherited retinal disease that causes early-onset severe visual impairment. To evaluate the mutation spectrum in the Chinese population, we performed a mutation screen in 145 Chinese LCA families.

Methods: First, we performed direct Sanger sequencing of 7 LCA disease genes in 81 LCA families. Next, we developed a capture panel that enriches the entire coding exons and splicing sites of 163 known retinal disease genes and other candidate retinal disease genes. The capture panel allowed us to quickly identify disease-causing mutations in a large number of genes at a relatively low cost. Thus, this method was applied to the 53 LCA families that were unsolved by direct Sanger sequencing of 7 LCA disease genes and an additional 64 LCA families. Systematic next-generation sequencing (NGS) data analysis, Sanger sequencing validation, and segregation analysis were used to identify pathogenic mutations.

Results: Homozygous or compound heterozygous mutations were identified in 107 families, heterozygous autosomal dominant mutations were identified in 3 families and an X-linked mutation was found in 1 family, for a combined solving rate of 76.6%. In total, 136 novel pathogenic mutations were found in this study. In combination with two previous studies carried out in Chinese LCA patients, we concluded that the mutation spectrum in the Chinese population is distinct compared to that in the European population. After revisiting, we also refined the clinical diagnosis of 10 families based on their molecular diagnosis.

Conclusions: Our results highlight the importance of a molecular diagnosis as an integral part of the clinical diagnostic process.

Figure 1

The segregation of mutations in families. Black: Affected. White: Unaffected. Square: Male. Circle: Female. Star: DNA not available. #Segregation test was done when DNA of family members were available. M, mutations.

Figure 2

The segregation of mutations in two genes in families. Black: Affected. White: Unaffected. Square: Male. Circle: Female. Star: DNA not available.

Figure 3

The phenotypes of the proband in family 171 and her affected brother 478. (A) The fundi of the proband in family171 showed macular dystrophy and attenuated retinal vessels with diffuse retinal mottling. (B) Optical coherence tomography of the proband in family 171 showed macular atrophy without noticeable signal of the junction between inner and outer segments. (C) The fundi of 478 showed diffuse retinal mottling in the middle peripheral retina. (D) Optical coherence tomography of 478 showed a relatively normal macular with weak IS/OS signal.

Figure 4

The percentage of LCA patients carrying mutations in CEP290, RPGRIP1, and CRB1 in Chinese and European ancestry patients.

Figure 5

The pedigree and the phenotype of family 104. (A) The pedigree of family 104. (B) Dilated fundus examination of the proband in family 104 showed obvious macular atrophy and scattered bone spicule pigmentation. (C) Optical coherence tomography indicated severe macular atrophy.

Figure 6

The phenotype of the proband in family 88. (A) Dilated fundus examination showed macular atrophy with yellow appearance and scattered bone spicule pigmentation. (B) Amelogenesis imperfecta.

Figure 7

The phenotypes of the proband in families 134 and 130. (A) Dilated fundus examination of the proband in family 134 showed bilateral macular coloboma-like lesion. (B) Optical coherence tomography of the proband in family 134 indicated severe macular atrophy. (C) Fundi of the proband in family 130 showed attenuated retinal vessels with pepper-salt and bone spicule pigmentation. (D) Optical coherence tomography of the proband in family 130 showed thinned retina with preserved signal of IS/OS in the central fovea.