These OVE427 mice harbor a mutation created by random insertion of two head-to-tail copies of the tyrosinase minigene (TYBS) transgene into the Ap2b1 (adaptor protein complex 2 β1 subunit) gene on chromosome 11. This results in a knockout allele; no β2-adaptin mRNA or protein is expressed from the mutant allele. Homozygous OVE427 mice exhibit complete clefting of the secondary palate (autosomal recessive nonsyndromic cleft palate) and die shortly after birth. Coronal cross-sections of the secondary palate of embryonic day (E)17 and E18 homozygous embryos display evidence of palatal shelf elevation and the apparent failure of the shelves to fuse. Ap2β1-deficiency also leads to reduced levels of another adaptor protein-2 (AP-2) complex protein, α-adaptin (Ap2a1). No craniofacial dysmorphology or any anomalies involving the limbs or developing skeleton are reported for OVE427 homozygotes. Other than cleft palate, additional histological examination through serial cross-sections of entire embryos do not reveal differences in major internal organs (heart, brain, lungs, kidneys, gastrointestinal tract) between wildtype and homozygous littermates.

Adaptor protein (AP) complexes are composed of subunits (adaptins) that are involved in the formation of intracellular transport vesicles and in the selection of cargo for incorporation into vesicles. The Ap2β1 (Ap2b1) gene encodes the β2-adaptin protein that, together with the α-adaptin protein (Ap2a1), the μ2 medium chain adaptin (Ap2m1), and the σ2 small chain adaptin (Ap2s1), assemble into the heterotetrameric adaptor protein-2 (AP-2) complex involved in clathrin-dependent endocytosis of receptors from the plasma membrane. These OVE427 mice are useful tools for studying the genetic components of cleft palate; including AP-2 complex assembly/function and defective endocytosis of one or more receptors or other cell surface proteins involved in palatogenesis.