Spatiotemporal expression pattern of keratins in skin of AP-2alpha-deficient mice.

Transcription factor AP-2alpha has been implicated as being a cell-type-specific regulator of gene expression during vertebrate embryogenesis based on its expression pattern in neural crest cells, ectoderm, and the nervous system in mouse and frog embryos. In mice, AP-2alpha is expressed in surface ectoderm beginning at the single cell layer state around E8.75. AP-2alpha-deficient mice, derived by targeted mutagenesis, display a severe ventral closure defect resulting in cranio-abdominoschisis and a hypoplasia of the cranial ganglia. This study analyzed the effect of a targeted disruption of the AP-2alpha gene on the architecture and the expression of intermediate filaments in skin. We analyzed skin samples from newborn mice and found no difference in either the morphology of the skin or the amount of intermediate filaments expressed. This suggests that despite the results from other analyses, loss of transcription factor AP-2alpha does not affect the expression of intermediate filaments in the skin of newborn animals. We found an altered spatial distribution of intermediate filament expression in the single layered cranial ectoderm during days 9-12 of gestation leading to an evenly distributed expression of keratin 5 and 15 in the mutants. Furthermore, the mutants lack a ring of ectodermal cells highly positive for keratin 15 in the area where lens induction occurs, indicating a defect in the inductive interactions underlying eye formation.