Complex segregation analysis of nonsyndromic cleft lip and palate.

This study was undertaken to examine the inheritance pattern of nonsyndromic cleft lip with or without cleft palate (CL/P). Complex segregation analysis using the unified model as in POINTER and the regressive model as in REGD programs were applied to analyze a midwestern U.S. Caucasian population of 79 families ascertained through a proband with CL/F. In REGD, the dominant or codominant Mendelian major locus models of inheritance were the most parsimonious fit. In POINTER, besides the Mendelian major locus model, the multifactorial threshold (MF/T) model and the mixed model were also consistent with the observed data. However, the high heritability parameter of .93 (SD .063) in the MF/T model suggests that any random exogenous factors are unlikely to be the underlying mechanisms, and the mixed model indicates that this high heritability is accounted for by a major dominant locus component. These findings indicate that the best explanation for the etiology of CL/P in this study population is a putative major locus associated with markedly decreased penetrance. Molecular studies may provide further insight into the genetic mechanism underlying CL/P.