Desmosomal junctions are abundant in epidermis and contain two classes of transmembrane
glycoprotein, the
desmocollins and the
desmogleins, which are members of the
cadherin superfamily of Ca(2+)-dependent
cell adhesion molecules. The
desmocollin subfamily includes DGIV/V and DGII/III while the
desmoglein subfamily includes DGI, HDGC and the
autoantigen of the blistering
skin disease pemphigus vulgaris (PVA). There are also several non-
glycosylated proteins, including the
desmoplakins and
plakoglobin, present in the desmosomal plaque, which forms a link between the
glycoproteins and the
cytokeratin intermediate filaments. To provide a picture of the expression of the desmosomal genes and their products in epidermis, we have used in situ hybridisation and immunofluorescence staining on sections of human foreskin. We find that, as expected,
desmoplakin DPI/II and
plakoglobin are expressed throughout the epidermis, gradually accumulating during differentiation, which probably reflects the increased numbers of desmosomes. In contrast, while
keratin 14 and the hemidesmosomal component
bullous pemphigoid antigen I (BPAGI) are basal-specific,
desmocollin DGIV/V is expressed only in the upper spinous/granular layers of the epidermis, whereas DGII/III expression is enriched in the basal layers. Amongst the
desmogleins, expression of DGI appears similar to
desmoplakin and
plakoglobin; PVA is more prevalent in the lower spinous layers, whereas HDGC expression is detected basally but not suprabasally. The major desmosomal
cadherin transcripts are
desmocollin DGIV/V and
desmoglein DGI. The resultant changes in desmosomal composition and structure may reflect the maturation of desmosomes, presumably being related to the need for changes in cell adhesion during stratification, terminal differentiation, and desquamation, and point to the desmosome being a key player in epidermal differentiation.