Changes in keratin and filaggrin expression in the skin of chronic proliferative dermatitis (cpdm) mutant mice

The expression of keratins and filaggrin by keratinocytes is a highly regulated process and depends on their state of differentiation and proliferation. As such, these proteins can be used as markers to determine if keratinocyte differentiation is normal. Mutant cpdm/cpdm mice develop a chronic skin disease characterized by epidermal hyperplasia and inflammation. Immunohistochemical staining for the basal keratins K5 and K14 revealed expression in the basal and suprabasal cell layers. The expression of K1 and K10 was reduced and limited to the outer layers of the stratum spinosum. Keratin 6 was expressed in the suprabasal layers of affected skin, and throughout all layers in severely affected skin. Filaggrin was present in the stratum granulosum which had variable thickness. These results indicate that the differentiation of keratinocytes in cpdm/cpdm mice was normal. The altered distribution and expression of keratins in comparison with the skin of control mice was the result of hyperproliferation.