Purpose PACG is one of the leading causes of blindness where lens thickness is a major risk factor for narrow-angle individuals. To our knowledge, no literature has been reported on candidate gene for lens thickness as a quantitative trait (QT). Here, we performed a genome-wide association analysis on lens thickness in the narrow-angle individuals. Materials and Methods We conducted a genome-wide association study (GWAS) in the narrow angle individuals to investigate comprehensive genetic insights on lens thickness. Results In QT-GWAS, we identified 145 genome-wide suggestive significant loci in the discovery cohort. Subsequently, we observed 13 SNPs that showed statistical significance around the region of PTRRM. Regional association analysis for top significant genotyped variants identified PTPRM as the most likely candidate for increased LT. Integrative bioinformatic analyses confirmed that the associated genomic region has potential regulatory roles for modulating transcription as enhancers. In the replication cohort, the sentinel genotype SNP was further associated significantly (P-value =0.000448) with high LT individuals. In both cohorts, the T allele of rs1941137 in the PTPRM gene indicates as a risk allele for the increased LT. Conclusion In this study, we discovered evidence of a genomic association between chromosomal areas around the PTPRM and increased lens thickness, resulting in a narrow angle. The regulatory components corresponding to PTPRM variations might have a role in the thicker lens. We report that the genomic region near PTPRM, a gene of potential interest, is associated with increased lens thickness.
BackgroundSarcoglycanopathies (SG) is the most frequent form of autosomal recessive limb-girdle muscular dystrophies (LGMD) leading to progressive muscle wasting and weakness, predominantly characterized by limb-girdle weakness. LGMDR4 is caused by mutations in SGCB encoding for the beta-sarcoglycan proteins. In this study, we describe a shared, common haplotype cosegregating in 14 SG cases from 13 unrelated families with the likely pathogenic homozygous mutation c.544A>C (p.Thr182Pro) in SGCB.MethodsThe genotypes of five selected markers (rs10009426, rs6824707, rs2271046, rs35414474 and rs17611952) surrounding the c.544A>C (p.Thr182Pro) were extracted from the variant call format (VCF) generated from whole-exome sequencing (WES) of 14 cases and 14 related family members as controls. The linkage data file was constructed and linkage disequilibrium (LD) plots were generated using HaploView to visualize patterns of LD. Further, haplotype reconstructions based on the 6 markers were conducted using PLINK1.9. using the expectation-maximization (EM) algorithm, an iterative method to find maximum likelihood. Subsequently, the R programming language was used to determine and compare plots of the haplotype frequencies and percentages for both groups to infer the risk haplotypes.ResultsFour strong LD blocks were identified in control group: rs10009426 to rs6824707 (0.27□kb), rs6824707 to rs2271046 (41.6 kb), rs10009426 to rs2271046 (41.8 kb) and rs35414474 to rs17611952 (0.17 kb) which were absent in the case group. Similarly, a total of nine haplotypes were estimated in cases and controls of which haplotype H1= G, A, T, G, G, T showed significant statistical difference in the frequency between cases and controls. H1 is also observed to cosegregate with c.544A>C (p.Thr182Pro) in the pedigrees of all the cases.ConclusionThe identification of c.544A>C (p.Thr182Pro) mutation in 14 cases from India indicates a probable event of founder effect. Further, the H1 haplotype, cosegregating with this mutation, convincingly sheds light on the recent developments in population genetics allowing insights into demographic and population history. This haplotype can also be used as a genetic marker to screen individuals with genetic susceptibility as carriers and provide genetically informed risk stratification and management in the prevention of SG.
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