Wnt9b is the mutated gene involved in multifactorial nonsyndromic cleft lip with or without cleft palate in A/WySn mice, as confirmed by a genetic complementation test

The noncomplementation of clf1 and Wnt9b- confirms that clf1 is a mutation of the Wnt9b gene. The homologous human WNT9B gene and 3' conserved noncoding region should be examined for a role in human nonsyndromic CLP.