DIFFERENTIAL EXPRESSION OF 4 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 t ranscription-PCR, and the expression of four connexin genes (Cx-43, -3 2, -30.3, and -26) was detected by in situ hybridization in internal a nd surrounding compartments of large antral follicles. Cx-43 and Cx-30 .3 were expressed in the theca interna as well as in the granulosa cel l compartment. However, two zones were observed in the theca interna b y probing with Cx-43; about a quarter of the region close to the lamin a basalis appeared devoid of Cx-43 messenger RNA (mRNA) and protein as well. Cx-30.3, in contrast, seemed to be expressed ubiquitously in th ese two compartments. Cx-26 and Cx-32 were expressed only in the theca l cells. Both Cx-43 and -30.3 also gave positive signals in the cumulu s cells to the same extent as obtained in the granulosa cells with the respective probes, whereas the expression of Cx-32 and -26 was undete ctable. Cx-43 mRNA drastically decreased in the functioning stage of t he corpus luteum, whereas Cx-30.3 mRNA increased significantly in the early stage of luteinization in the estrus cycles. These results sugge st 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 se em to be expressed, and their expressions are regulated differently.