Differential expression of the gap junction proteins connexin45, -43, -40, -31, and -26 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 embryonic and adult mouse skin. For this purpose, polyclonal antibodies to Cx31 and Cx45 were raised by immunizing rabbits with fusion proteins of glutathione S-transferase and carboxy-terminal peptides including 65 amino acids of Cx31 or 138 c-terminal amino acids of Cx45, respectively. Here we describe characterization of the affinity-purified Cx31 antibodies in human HeLa cells, transfected with mouse Cx31 coding DNA, and in mouse keratinocyte-derived cell lines. In the epidermis of embryonic mice at day 19 of gestation Cx43 and -45 were detected in the basal layer, while the stratum spinosum showed expression of Cx43, -31 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 and in addition Cx40 was weakly expressed in the stratum basale. Furthermore, during hair development, Cx31 was detected in the inner epithelial 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 sebaceous glands. Cx31 was also demonstrated in 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 differential expression of five different connexin proteins, suggesting specific and coordinated function(s) of gap junctional communication during skin and hair development.