Objective To identify and observe disease-causing gene variants and clinical phenotypes in a Han Chinese family with Leber congenital amaurosis(LCA).Methods A retrospective study.A patient with LCA10 and his parents who had presented at Department of Ophthalmology of Henan Provincial People's Hospital on May 2022 were selected as the study subject.Detailed medical and family histories were recorded,fundus photography and flash electroretinogram(F-ERG)were performed.Peripheral venous blood samples(3 ml)of the proband and his parents were collected to extract whole genomic DNA,then whole exome sequencing(WES)and mitochondrial DNA(mtDNA)sequencing were carried out for the proband to determine the disease-causing gene and variants.All variants were annotated by bioinformatics analysis.According to the American College of Medical Genetics and Genomics(ACMG)guidelines,the pathogenicity of all detected variants were evaluated.Candidate variants were verified by Sanger sequencing,and in vitro minigene assay were performed to evaluate the impact of the missense variant with insufficient evidence on mRNA splicing.Results The proband,male,7-month-old,presented with an inability to follow light or objects,eye poking,photophobia,nystagmus,partial loss of retinal pigment epithelium around the fovea of the macula.At the age of 2 years old,F-ERG revealed severe reduction,elongation,or even no waveform of a-wave and b-wave in both eyes.No obvious abnormality was found in the clinical phenotype of his parents.The result of WES revealed that the proband carried two variants in exon 40 and exon 2 of CEP290,a frameshift variant c.5515_5518del(p.Glu1839Lysfs*11)(V1)and a novel missense variant c.74C＞T(p.Ala25Val)(V2),respectively.The result of mitochondrial DNA sequencing was negative.Sanger sequencing confirmed that the heterozygous frameshift variant was inherited from his father and the heterozygous novel missense variant was inherited from his mother,which constituted compound heterozygous variants.In vitro minigene splicing assay confirmed that V2 created a new splicing donor at exon 2,leading to the in-frame deletion of 30bp fragment during transcription and loss of 10 amino acid residues in the protein.The two variants were pathogenic(V1)and likely pathogenic(V2)based on ACMG guidelines,respectively.Conclusions The c.5515_5518del and novel c.74C＞T compound heterozygous variants of the CEP290 gene probably are the cause of LCA10 in this family,which lead to the production of a truncated protein and aberrant splicing of pre-mRNA,respectively.LCA is characterized by early onset,severe impairment of visual function,and a wide range of disease-causing variations.
关键词
Leber先天性黑矇10型/CEP290基因/全外显子组测序/Minigene剪接验证
Key words
Leber congenital amaurosis type 10/CEP290 gene/Whole exome sequencing/Minigene splicing assay
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