Detection of Variants in 15 Genes in 87 Unrelated Chinese Patients with Leber Congenital Amaurosis

Abstract

BackgroundLeber congenital amaurosis (LCA) is the earliest onset and most severe form of hereditary retinal dystrophy. So far, full spectrum of variations in the 15 genes known to cause LCA has not been systemically evaluated in East Asians. Therefore, we performed comprehensive detection of variants in these 15 genes in 87 unrelated Han Chinese patients with LCA.Methodology/Principal FindingsThe 51 most frequently mutated exons and introns in the 15 genes were selected for an initial scan using cycle sequencing. All the remaining exons in 11 of the 15 genes were subsequently sequenced. Fifty-three different variants were identified in 44 of the 87 patients (50.6%), involving 78 of the 88 alleles (11 homozygous and 56 heterozygous variants). Of the 53 variants, 35 (66%) were novel pathogenic mutations. In these Chinese patients, variants in GUCY2D are the most common cause of LCA (16.1% cases), followed by CRB1 (11.5%), RPGRIP1 (8%), RPE65 (5.7%), SPATA7 (4.6%), CEP290 (4.6%), CRX (3.4%), LCA5 (2.3%), MERTK (2.3%), AIPL1 (1.1%), and RDH12 (1.1%). This differs from the variation spectrum described in other populations. An initial scan of 55 of 215 PCR amplicons, including 214 exons and 1 intron, detected 83.3% (65/78) of the mutant alleles ultimately found in these 87 patients. In addition, sequencing only 9 exons would detect over 50% of the identified variants and require less than 5% of the labor and cost of comprehensive sequencing for all exons.Conclusions/SignificanceOur results suggest that specific difference in the variation spectrum found in LCA patients from the Han Chinese and other populations are related by ethnicity. Sequencing exons in order of decreasing risk is a cost-effective way to identify causative mutations responsible for LCA, especially in the context of genetic counseling for individual patients in a clinical setting.

A Comprehensive Review of Mutations in the MERTK Proto-Oncogene

“…The pathological implication of some heterozygous missense substitutions present in both patients and their unaffected parents is not clear (p.Glu540Lys, p.Ser661Cys, p.Ile871Thr) (Gal et al 2000). Yet, heterozygous mutations in Leber Congenital Amaurosis cases seem to co-segregate with other gene defects (p.Phe214Val, p.Pro958Leu) (Li et al 2011). Taken together, these data suggest that some variants might be pathogenic in combination with other factors.…”

Detection of CRB1 mutations in families with retinal dystrophy through phenotype-oriented mutational screening

“…Clinical phenotypes in this study were mainly based on the fundus photos and the age of onset (1-10 years of age). CRB1-associated characteristic clinical findings included: i) severe early onset retinal dystrophy (including LCA and early onset RP) (4,; ii) nummular pigmentary changes at the posterior fundus; iii) preservation of the para-arteriolar retinal pigment epithelium (PPRPE) (14); iv) Coats-like vasculopathy (CLV) (12); and v) pigmented paravenous chorioretinal atrophy (PPCRA) (20).…”

“…Genomic DNA was prepared from venous leukocytes using a method described previously (32). The procedure for Sanger sequencing of CRB1 was the same as that described in our previous study and the same sets of primers were used (4). The informatics analysis for the detected variants was also as described previously (4).…”

“…The procedure for Sanger sequencing of CRB1 was the same as that described in our previous study and the same sets of primers were used (4). The informatics analysis for the detected variants was also as described previously (4). Only homozygous or compound heterozygous variants that were predicted to be pathogenic were considered to be disease-causing because: i) CRB1 mutations were only reported to associate with recessive retinal dystrophy (8); and ii) single heterozygous null mutations for recessive genes were common in the general population (33).…”

“…Mutations in crumbs homolog (CRB)1 are among the common causes of severe early onset retinal dystrophy, including LCA and early onset RP (4,. Although a firm genotype-phenotype correlation between CRB1 mutations and specific phenotypes has yet to be determined, some characteristic clinical findings have been suggested to associate with CRB1 mutations.…”