Despite the robust expression of Lhx6 and Lhx7 in neural crest-derivatives of the first branchial arch (Grigoriou et al., 1998), mice homozygous for single gene deletions show no defects in the formation of teeth or other cranial skeletal structures, apart from cleft palate that has been observed in a percentage (approx. 70%) of Lhx7-deficient animals (Zhao et al., 1999; our observations). Here, LHX6 is linked to cleft palate.