Expression and localization of tight, adherens, and gap junction proteins in the chicken ovary during pause in laying induced by fasting.

Intercellular junctions are critical to normal functioning and remodeling of various tissues in the reproductive system; however, their importance in the avian ovary is poorly understood. The aim of this study was to examine the expression and localization of essential tight (claudin 1, occludin, zonula occludens 1 [ZO1 gene]), adherens (E-cadherin [CDH1], β-catenin [CTNNB1]), and gap (connexin 43 [GJA1]) junction proteins in the hen ovarian follicles during a pause in laying induced by fasting. 32-week-old Hy-Line Brown hens were randomly divided into two groups: the control group (fed ad libitum; n = 8) and the experimental group (fasted; n = 8), which was subjected to an induced pause in egg laying by complete feed withdrawal for five consecutive days. Tissue samples from prehierarchical (white and yellowish) and hierarchical (small yellow and the largest yellow preovulatory F3-F1) follicles were collected on day six of the experiment from the control hens (laying) and hens that had been fasted (non-laying). Quantitative RT-PCR and Western blot analyses showed differences in the expression of examined proteins on mRNA and/or protein levels between the white and yellowish follicles, as well as between the largest yellow preovulatory F3-F1 follicles and the theca and granulosa layers of these follicles. Immunofluorescence revealed differences in staining intensity between the layers of follicle wall, with localization of all proteins mainly in the granulosa layer. In fasted hens, the atresia of the largest yellow follicles was accompanied by: (1) no changes in mRNA transcript abundance of tight and adherens junction proteins in prehierarchical follicles, and a decrease in GJA1 mRNA level in the white follicles; (2) mostly a decrease in mRNA transcript levels of each type of molecules in the yellow atretic follicles; (3) a decrease, no changes, or an increase in examined protein abundances in the white and yellowish follicles; (4) a decrease in cell junction protein abundances in F3-F1 follicles; and (5) a marked reduction in immunoreactivity for occludin, E-cadherin, β-catenin, and connexin 43 in the wall of atretic follicles. Our results provide novel insights into the molecular composition of tight, adherens, and gap junctions and their contribution to the remodeling of the follicular wall during follicle development and fasting-induced atresia of yellow preovulatory follicles in hens.