Modifier gene candidates in charcot-marie-tooth disease type 1A: A case-only genome-wide association study

Background: Charcot-Marie-Tooth disease type 1A (CMT1A) is caused by a uniform 1.5-Mb duplication on chromosome 17p, which includes the PMP22 gene. Patients often present the classic neuropathy phenotype, but also with high clinical variability. Objective: We aimed to identify genetic variants that are potentially associated with specific clinical outcomes in CMT1A. Methods: We genotyped over 600,000 genomic markers using DNA samples from 971 CMT1A patients and performed a case-only genome-wide association study (GWAS) to identify potential genetic association in a subset of 644 individuals of European ancestry. A total of 14 clinical outcomes were analyzed in this study. Results: The analyses yielded suggestive association signals in four clinical outcomes: difficulty with eating utensils (lead SNP rs4713376, chr6 : 30773314, P = 9.91×10^-7, odds ratio = 3.288), hearing loss (lead SNP rs7720606, chr5 : 126551732, P = 2.08×10^-7, odds ratio = 3.439), decreased ability to feel (lead SNP rs17629990, chr4 : 171224046, P = 1.63×10^-7, odds ratio = 0.336), and CMT neuropathy score (lead SNP rs12137595, chr1 : 4094068, P = 1.14×10^-7, beta = 3.014). Conclusions: While the results require validation in future genetic and functional studies, the detected association signals may point to novel genetic modifiers in CMT1A.