Stage-specific and differential expression of gap junctions in the mouse ovary: connexin-specific roles in follicular regulation

Abstract

ResearchGap junction communication plays an essential role in follicle growth. Immunocytochemistry and confocal microscopy were used to examine the expression of gap junction connexins of the α and β subfamilies in follicles from primordial to preovulatory stages in the ovaries of prepubertal and adult mice. Connexin-specific antibodies detected α 1 , α 4 , α 6 , β 1 , β 2 and β 4 connexins within follicles. In adult ovaries connexin immunolabelling was stronger in larger (more mature) follicles than it was in smaller follicles, with comparatively reduced labelling detected in prepubertal ovaries. In healthy follicles, labelling for α subfamily connexins was detected between granulosa cells, whereas labelling for β subfamily connexins was found in the theca. Labelling for β subfamily connexins and α 4 connexin (preantral stage) was detected on the oocyte surface membrane. In atretic follicles, labelling for β 4 connexin appeared between the granulosa cells. These results demonstrate that α and β connexin subfamilies are segregated to separate cellular compartments in the mouse follicle. The results are discussed in the light of possible roles for differential gap junctional communication in the regulation of folliculogenesis, oocyte maturation and atresia.

Functional analysis of gap junctions in ovarian granulosa cells: distinct role for connexin43 in early stages of folliculogenesis

“…19), Cx43 is the only gap junction protein that has been clearly shown to be expressed by the granulosa cells of early preantral follicles of the mouse (17,37). Thus the follicle arrest in Cx43-deficient ovaries may be due to a complete absence of connexins from the granulosa cells.…”

“…Collectively, these results suggest that the granulosa cells of preantral follicles express one or more connexins other than Cx43 but that this other connexin does not normally assemble into functional gap junctions in the absence of Cx43. The other connexin(s) could be Cx32, Cx37, Cx45, or Cx57, all of which are reported to be expressed along with Cx43 in granulosa cells of mature mouse follicles (19,37). Such a rare connexin, coexpressed with Cx43 in granulosa cells of early follicles, might contribute more significantly to gap junction assembly later in folliculogenesis as gap junctions become larger and more numerous.…”

“…Although dye transfer was limited to first-order cells, this suggested the presence of another connexin(s). Indeed, granulosa cells in mature rodent follicles do express other connexins in addition to Cx43, including Cx32 (24, 35), Cx45 (2,19,28), Cx37 (37), and possibly Cx57 (the gene encoding Cx57 is transcribed in the mouse ovary, and its porcine homolog, Cx60, has been identified in cumulus granulosa cells; Refs. 15,25).…”

Advancement in Molecular Genetics to understand the molecular reproduction of Livestock – follicular development

“…The proteins connexins is the principle component of gap junction. It has been demonstrated that connexins 32, 37, 43, 45 and 57 have been detected within growing and mature mouse follicles (Wright et al, 2001). However, in cattle, connexin expression shows in a stage specific manner; for instance, Cx26 is expressed in oocytes of primordial, primary and secondary follicles and in the granulosa of healthy antral follicles (Johnson et al, 1999).…”

Cell cycle dependent regulation of gap junction coupling and apoptosis in GFSHR-17 granulosa cells

“…Similarly, a PKC-dependent phosphorylation of Cx43 that correlates with a reduction of gap junction coupling was found during G2/M phase of the cell cycle [11] GFSHR-17 granulosa cells, the in vitro model for granulosa cells of the maturing ovular follicle, are a suitable cell system for the analysis of gap junction coupling and apoptosis [12]. They form gap junction channels mainly formed by Cx43 and Cx45 [13], which regulate follicular development and atresia [14][15][16]. Moreover, granulosa cells in the ovular follicles are eliminated by apoptosis during atresia or the deterioration of the corpus lu-teum [17,18].…”