Ultrastructural localization of basigin in normal human epidermis

Basigin is a glycosylated transmembrane protein belonging to the immunoglob ulin superfamily. It is thought to play roles in intercellular recognition involved in cell differentiation. We previously demonstrated at the light m icroscope level a correlation between basigin expression and epidermal diff erentiation. In the present study, the ultrastructural localization of basi gin in normal human epidermal keratinocytes was investigated by immunoelect ron microscopy. The basigin labeling was strongest on membranes of basal ce lls, weaker on prickle cells, and absent in granular and horny cells. On th e membrane of basal cells, labeling was observed on the apical and lateral sides but not on the dermal side. Gold particles were mostly observed on th e surface of microvilli, especially on their tips. There were fewer on the intermicrovillous membrane and they were absent on the desmosome. These res ults are consistent with our previous report that basigin expression is cor related with differentiation of epidermal keratinocytes. Microvilli on basa l and suprabasal keratinocytes might play roles in the differentiation of k eratinocytes through basigin on the tips of microvilli.