CD44 EXPRESSION ON EPIDERMAL MELANOCYTES

We examined CD44 expression on melanocytes to begin to understand what role CD44 might have in the normal behavior of melanocytes and to pro vide a basis for comparing CD44 expression in melanoma cells. CD44 was expressed on the entire surface of melanocytes and accentuated at the tips of dendritic processes. Two predominant forms of CD44 are expres sed on cultured human foreskin melanocytes. One form has the covalent addition of chondroitin sulfate, whereas the other form has no chondro itin sulfate. Both use the hematopoietic, or CD44H, core protein. Usin g polymerase chain reaction primers that span the site where alternati ve splicing of CD44 occurs, we found only the cDNA coding CD44H. 12-O- Tetradecanoylphorbol 13-acetate increases the size of the chondroitin sulfate chain(s) attached to CD44 but not the proportion of CD44 molec ules that carry chondroitin sulfate. Ninety percent of proteoglycans o n melanocytes are chondroitin sulfate proteoglycans, and the CD44 chon droitin sulfate proteoglycan represented 10% of that total. These data show that CD44H is expressed as a ''part-time'' chondroitin sulfate p roteoglycan on normal cultured melanocytes.