EDITOR'S CHOICE Disruption of the Murine Ap2β1 Gene Causes Nonsyndromic Cleft Palate

Development of the secondary palate in mammals is a complex process that can be easily perturbed, leading to the common and distressing birth defect cleft palate Animal models are particularly useful tools for dissecting underlying genetic components of cleft palate We describe a new cleft palate model resulting from a transgene insertion mutation Transgene insertional mutagenesis disrupts the genomic organization and expression of the Ap2 beta 1 gene located on chromosome 11 This gene encodes the beta 2-adaptin subunit of the heterotetrameric adaptor protein 2 complex involved in clathrin-dependent endocytosis Homozygous cleft palate mutant mice express no Ap2 beta 1 messenger RNA or beta 2-adaptin protein and die during the perinatal period Heterozygous mice are phenotypically normal despite expressing diminished beta 2-adaptin messenger RNA and protein compared with wildtype Remarkably, the paralogous beta 1-adaptin subunit of the adaptor protein 1 complex partially substitutes for the missing beta 2-adaptin in embryonic fibroblasts from homozygous mutant mice, resulting in assembly of reduced levels of an adaptor protein 2 complex bearing beta 1-adaptin This variant adaptor protein 2 complex is, therefore, apparently capable of maintaining viability of the homozygous mutant embryos until birth but insufficient to support palatogenesis Nonsyndromic cleft palate in an animal model is associated with disruption of the Ap2 beta 1 gene