TISSUE-SPECIFIC AND STRATUM-SPECIFIC EXPRESSION OF THE HUMAN INVOLUCRIN PROMOTER IN TRANSGENIC MICE

Involucrin is a marker of keratinocyte terminal differentiation and is expressed only in the suprabasal layers of stratified squamous epithe lium. In a previous study with various cell types in culture, we noted that expression of the putative human involucrin promoter was keratin ocyte specific. To determine if this promoter is sufficient to direct expression to the suprabasal cells of stratified squamous epithelia in vivo, we have now generated transgenic mouse lines harboring the invo lucrin promoter sequences linked to a beta-galactosidase reporter gene . In the resulting lines, beta-galactosidase was expressed in the supr abasal compartment of stratified squamous epithelia and in hair follic les in a tissue-specific manner. In the palate, distinct vertical stac ks of beta-galactosidase-expressing cells were present, suggesting mov ement of clonally derived cells through the epithelium. The involucrin gene has a single intron upstream of the translational start site, an d removal of this intron did not affect tissue- or stratum-specific ex pression. These results show that the 3.7-kb involucrin upstream seque nces contain all the information necessary for a high level of tissue- and stratum-specific expression.