Analyses of previous data have confirmed the contribution of the IRF6 gene to susceptibility to nonsyndromic oral clefts (NSOC) in some populations. We tested for associations between the rs2013162, rs2235375, and rs2235371 polymorphisms in IRF6 and the risk of NSOC, using both case-parent trio and case-control designs on samples from western China. Our study group consisted of 332 persons with NSOC, their parents (289 mothers and 243 fathers for 206 complete trios for these three SNPs), and 174 control individuals. We found strong evidence of over-and undertransmission of the C allele (the Val allele) at rs2235371, and the C allele at rs2235375 in cleft caseparent trios (P = 0.013 and P = 0.000, respectively). There were significant differences in the frequency distributions of both genotypes and alleles when cases were compared with control infants at rs2235371 and rs2235375. Five specific haplotypes showed significant over-and undertransmission. These results further support a role for IRF6 variants in western Chinese populations.

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