Association between IIRF6, TP63, GREM1/I Gene Polymorphisms and Non-Syndromic Orofacial Cleft Phenotypes in Vietnamese Population: A Case–Control and Family-Based Study

This study aims to identify potential variants in the TP63–IRF6 pathway and GREM1 for the etiology of non-syndromic orofacial cleft (NSOFC) among the Vietnamese population. By collecting 527 case–parent trios and 527 control samples, we conducted a stratified analysis based on different NSOFC phenotypes, using allelic, dominant, recessive and over-dominant models for case–control analyses, and family-based association tests for case–parent trios. Haplotype and linkage disequilibrium analyses were also conducted. IRF6 rs2235375 showed a significant association with an increased risk for non-syndromic cleft lip and palate (NSCLP) and cleft lip with or without cleft palate (NSCL/P) in the G allele, with p[sub.allele] values of 0.0018 and 0.0003, respectively. Due to the recessive model (p = 0.0011) for the NSCL/P group, the reduced frequency of the GG genotype of rs2235375 was associated with a protective effect against NSCL/P. Additionally, offspring who inherited the G allele at rs2235375 had a 1.34-fold increased risk of NSCL/P compared to the C allele holders. IRF6 rs846810 and a G-G haplotype at rs2235375–rs846810 of IRF6 impacted NSCL/P, with p-values of 0.0015 and 0.0003, respectively. In conclusion, our study provided additional evidence for the association of IRF6 rs2235375 with NSCLP and NSCL/P. We also identified IRF6 rs846810 as a novel marker associated with NSCL/P, and haplotypes G-G and C-A at rs2235375–rs846810 of IRF6 associated with NSOFC.