rs1801133C>T polymorphism in MTHFR is a risk factor for nonsyndromic cleft lip with or without cleft palate in the Brazilian population.

Background: The MTHFR rs1801131A>C and rs1801133C>T variants have been analyzed as putative genetic risk factors for oral clefts within various populations worldwide.

Methods: To test the role of these polymorphisms in nonsyndromic cleft lip with or without cleft palate (NSCL/P) in the Brazilian population, we conducted a study combining a Family-Based Association Test (transmission disequilibrium test) and a structured association analysis (case-control study) based on the individual ancestry proportions. The rs1801131 and rs1801133 were initially analyzed in 197 case-parent trios by transmission disequilibrium test, and polymorphisms showing significant association with NSCL/P were subsequently studied in independent sample composed of 318 isolated samples of NSCL/P and 598 healthy controls in a case-control approach.