Screening of a large cohort of Leber congenital amaurosis andretinitis pigmentosa patients identifies novel LCA5 mutationsand new genotype-phenotype correlations

摘要

To investigate the prevalence of sequence variants in LCA5 in patients with Leber congenital amaurosis (LCA), early onset rod-cone dystrophy (EORD) and autosomal recessive retinitis pigmentosa (RP), to delineate the ocular phenotypes, and to provide an overview of all published LCA5 variants in an online database._Patients underwent standard ophthalmic evaluations after providing informed consent. In selected patients, optical coherence tomography (OCT) and fundus autofluorescence imaging was possible. DNA samples from 797 unrelated patients with LCA and 211 with the various types of RP were screened by Sanger sequence analysis of all LCA5 exons and intron/exon junctions. Some LCA patients were pre-screened by APEX technology or selected based on homozygosity mapping. In silico analyses were performed to assess the pathogenicity of the variants. Segregation analysis was performed where possible. Published and novel LCA5 variants were collected, amended for their correct nomenclature, and listed in a Leiden Open Variation Database (LOVD). Sequence analysis identified 18 new probands with 19 different LCA5 variants. Seventeen of the 19 LCA5variants were novel. Except for two missense variants and one splice sitevariant, all variants were protein-truncating mutations. Most patients expresseda severe phenotype, typical of LCA. However, some LCA subjects had better visionand intact inner segment/outer segment (IS/OS) junctions on OCT imaging. In twofamilies with LCA5 variants, the phenotype was more compatiblewith EORD with affected individuals displaying preserved islands of RPE. One ofthese milder families harbored a homozygous splice site mutation, a secondfamily was found to have a combination of a stop mutation and a missensemutation. This is the largest LCA5 study to date. We sequenced1008 patients (797 with LCA, 211 with arRP) and identified 18 probands withLCA5 mutations. Mutations in LCA5 are arare cause of childhood retinal dystrophy accounting for ~2% of diseasein this cohort and the majority of LCA5 mutations are likelynull. The LCA5 protein truncating mutations are predominantlyassociated with LCA. However, in two families with the milder EORD, theLCA5 gene analysis revealed a homozygous splice sitemutation in one and a stop mutation in combination with a missense mutation in asecond family, suggesting that this milder phenotype is due to residual functionof lebercilin and expanding the currently known phenotypic spectrum to includethe milder early onset RP. Some patients have remaining foveal cone structures(intact IS/OS junctions on OCT imaging) and remaining visual acuities, which maybode well for upcoming treatment trials.