Genetic analysis of the CACNA1F gene in a family affected with incomplete form Schubert-Bornschein type congenital stationary night blindness / 中华眼底病杂志

ABSTRACT

Objective:To determine the pathogenic gene mutation in a family with incomplete congenital quiescent night blindness (CSNB) of Schubert-Bornschein type.Methods:A retrospective clinical study. In February 2021, one patient and his parents and elder brother from a Han Chinese incomplete CSNB of Schubert-Bornschein type family diagnosed by clinical and genetic examination at Henan Provincial People's Hospital were included in the study. The patient’s medical history, family history were inquired; best corrected visual acuity (BCVA), color vision, fundus color photography, full-field electroretinogram (ERG), and frequency domain optical coherence tomography (OCT) were examined in detail. Five ml of the subject’s peripheral venous blood was collected and the whole genome DNA was extracted. The genomic DNA of the subject was library constructed, and all-exon probes were polymerized for capture. The suspected pathogenic mutation site was verified by Sanger, and the pathogenicity of the gene mutation site was determined by parallel bioinformatics analysis.Results:The BCVA of both eyes of the proband (Ⅱ2) was 0.4; the color vision test could not recognize the red color. Fundus examination showed no obvious abnormalities. The retina thickness in the macular area of both eyes was slightly thinned. ERG examination of the whole field showed that the amplitude of ERG b wave was significantly reduced under the stimulation of binocular dark adaptation 3.0 and showed a negative waveform. The mother of the proband (Ⅰ2) had normal BCVA, color vision, fundus color photography, and frequency domain OCT examination. The full-field ERG examination showed that the amplitude of each eye reaction was slightly reduced, and the amplitude of the dark adaptation shock potential was significantly reduced. Genetic testing showed that the proband (Ⅱ2) had a c.1761dupC hemizygous mutation in exon 14 of the voltage-dependent calcium channel α1F subunit gene ( CACNA1F gene). The results of protein sequence homology analysis showed that the site was highly conserved in multiple species; the results of bioinformatics analysis showed that the CACNA1F gene c.1761dupC (pY588fs) subsequently had a frameshift mutation and became a stop at position 10. Codons appear translational termination in the conserved regions of the protein. According to the standards and guidelines of the American College of Medical Genetics and Genomics, the mutation was judged to be a possible pathogenic variant. The mother of the proband (Ⅰ2) was a carrier of this site mutation. The clinical and genetic test results of the father and elder brother of the proband were not abnormal. Conclusion:CACNA1F gene c.1761dupC is the pathogenic mutation site of the Schubert-Bornschein type incomplete CSNB family.