Fuchs Endothelial Corneal Dystrophy associated risk variant, rs3768617 in LAMC1 shows allele specific binding of GFI1B.

Aims: To investigate the genetic and functional association of an intronic variant of LAMC1, rs3768617 with Fuchs endothelial corneal dystrophy (FECD) in the Indian population.
Methods: Blood samples were collected from age and sex matched 356 controls and 120 FECD patients after a detailed assessment via specular microscopy. Genomic DNA was extracted and genotyping was done by fluorescence based capillary electrophoresis. The genetic association of rs3768617 polymorphisms was computed by the chi-square (χ ² ) test. Bioinformatics studies were performed to find the allele specific binding of different transcription factors in the region of rs3768617 and functional evaluation assessed by luciferase assay followed by Electrophoretic Mobility Shift Assay (EMSA) and Chromatin Immunoprecipitation assay (ChIP). Immunofluorescence assay was carried out to check for any differential expression of GFI1B between control and FECD endothelium samples.
Results: SNP rs3768617 {chr1:183123365 (GRCh38.p13)} was found to be genetically associated with FECD in Indian population (p = 2.646 × 10 ^-8 ). Luciferase assay suggested that the rs3768617 locus has a regulatory role. In silico analysis showed that the transcription factor, GFI1B binds to the risk allele 'G' of rs3768617, but not to the protective allele 'A' which was also experimentally validated by EMSA. High enrichment of DNA flanking the surrounding region of rs3768617 was also found in presence of GFI1B specific antibody in ChIP assay. There was a 0.63 fold decrease in GFI1B expression in FECD affected corneal endothelium compared to control endothelium.
Conclusions: The genetic association of rs3768617 in LAMC1 with FECD pathogenesis is mediated by GFI1B, thus finding the functional role of LAMC1 in FECD pathogenesis.
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