DIFFERENTIAL EXPRESSION OF THE GAP JUNCTION PROTEINS CONNEXIN45, CONNEXIN43, CONNEXIN40, CONNEXIN31, AND CONNEXIN26 IN MOUSE SKIN

The expression of five different members of the gap junction multigene family, connexin (Cx)45, -43, -40, -31, and -26 was investigated in e mbryonic and adult mouse skin. For this purpose, polyclonal antibodies to Cx31 and Cx45 were raised by immunizing rabbits with fusion protei ns of glutathione S-transferase and carboxy-terminal peptides includin g 65 amino acids of Cx31 or 138 c-terminal amino acids of Cx45, respec tively Here we describe characterization of the affinity-purified Cx31 antibodies in human HeLa cells, transfected with mouse Cx31 coding DN A, and in mouse keratinocyte-derived cell lines. In the epidermis of e mbryonic mice at day 19 of gestation Cx43 and -45 were detected in the basal layer, while the stratum spinosum showed expression of Cx43, -3 1 and -26. In the stratum granulosum we found expression of Cx31 and - 26. In the epidermis of adult mice Cx43 and -31 were located similarly as in embryonic tissue, but Cx45 as well as Cx26 were not detected an d in addition Cx40 was weakly expressed in the stratum basale. Futherm ore, during hair development, Cx31 was detected in the inner epithelia l root sheath and sebaceous glands of hair follicle. Cx43 and -40 were found in the outer epithelial root sheath and to a lesser extent in s ebaceous glands. Cx31 was also demonstrated is Hel-37 and Hel-30, i.e. two related cell lines derived from mouse keratinocytes. Our results show that epidermal and follicular differentiation coincides with diff erential expression of five different connexin proteins, suggesting sp ecific and coordinated function(s) of gap junctional communication dur ing skin and hair development.