In humans, mutations in the Msx1 gene have been implicated in tooth agenesis (Padanilam et al., 1992; Hu et al., 1998) and cleft palate (Van Den Boogaard et al., 2000), and the phenotype was proposed to be related to a dose effect of Msx1 protein (Hu et al., 1998). The gene discussed is MSX1; the disease is cleft palate.