Characterization of desmosomal component expression during palatogenesis.

Adhesion of the opposing palatal shelves is a critical first step in the mechanism for palatal fusion. Formation of desmosomal junctions between the two medial edge epithelia provides a mechanism for palatal shelf adhesion. RT-PCR and immunohistochemistry were used to determine the pattern of expression of desmosomal components during palatogenesis. Desmosomal expression was specifically upregulated in the medial edge epithelia (MEE) at the early stages of palatal fusion as detected by both immunohistochemistry and electron microscopy. RT-PCR characterization of the desmosomal components detected all known elements, except desmocollin 1 (DSC1). Desmocollin 2 (DSC2) was expressed as both the DSC2a and DSC2b variants. The two variants are expressed at the same level. Western analysis of desmoglein expression paralleled the RT-PCR result. The temporal and spatial upregulation of desmosomal gene expression is evidence that the MEE induce new gene expression required to accomplish palatal shelf adhesion and initiate the first stage of palatal fusion.