α 6 subunit of integrins in the development and sex differentiation of the mouse ovary

The localization of the α 6 subunit of integrins in the ovary was studied by conventional and immunolabeling light and electron microscopy starting from the pregonadal embryonic phase until adulthood. The formation of gonadal blastema cells included an initial expression of the α 6 subunit on the plasma membranes of all blastema cells. Subsequently the reaction for the α 6 subunit became restricted in groups of these cells, which differentiated into gonadal cord cells, the precursors of follicular cells. The α 6 subunit was also found in the cells of the mesonephric duct, mesonephric tubules, and the ovarian rete. Reorganization of the gonadal cords into follicles at birth was accompanied with strong and uniform re‐expression of the α 6 subunit on the surface of the cord cells. Vascular endothelial cells and the cells of the postnatal surface epithelium remained positive for the α 6 integrin subunit. In larger follicles, the intensity of the reaction for the integrin subunit varied. The theca cells of growing follicles contained the α 6 subunit. The results show that this subunit of integrins is present in phases of increased adhesion and aggregation, and that its expression probably is involved in the regulation of ovarian epithelial differentiation. The distribution of α 6 integrin in ovarian cells shows potentially important sex‐specific and developmental differences in epithelial organization when compared with respective changes found earlier by us in the male gonad. © 1995 Wiley‐Liss, Inc.