Differential expression of four connexin genes, Cx-26, Cx-30.3, Cx-32, and Cx-43, in the porcine ovarian follicle

Connexin genes expressed in porcine ovaries were isolated by reverse transcription-PCR, and the expression of four connexin genes (Cx-43, -32, -30.3, and -26) was detected by in situ hybridization in internal and surrounding compartments of large antral follicles. Cx-43 and Cx-30.3 were expressed in the theca interna as well as in the granulosa cell compartment. However, two zones were observed in the theca interna by probing with Cx-43; about a quarter of the region close to the lamina basalis appeared devoid of Cx-43 messenger RNA (mRNA) and protein as well. Cx-30.3, in contrast, seemed to be expressed ubiquitously in these two compartments. Cx-26 and Cx-32 were expressed only in the thecal cells. Both Cx-43 and -30.3 also gave positive signals in the cumulus cells to the same extent as obtained in the granulosa cells with the respective probes, whereas the expression of Cx-32 and -26 was undetectable. Cx-43 mRNA drastically decreased in the functioning stage of the corpus luteum, whereas Cx-30.3 mRNA increased significantly in the early stage of luteinization in the estrus cycles. These results suggest that Cx-43 is not the only gap junction protein to be expressed in the ovarian follicle; other proteins, such as Cx-32, -30.3, and -26 seem to be expressed, and their expressions are regulated differently.