The expression of BH3-only Bcl-2 family members in mouse ovary and influence of gonadotropin on Nix expression in granulosa cells

Hwang, Seong Jin; Kim, Mee Ran; Kim, Jin Hong

Abstract

OBJECTIVE
In the ovary apoptosis eliminates granulosa cells (GC) during follicle atresia. While we identified many cell death regulatory molecules not yet characterized in the ovary, of particular interest were members of the Bcl-2 family which contain only the Bcl-2 homology (BH)-3 domain. The objectives of this study was to investigate and compare the expression patterns of BH3-only Bcl-2 family members in various organs and evaluate their function in ovarian granulosa cells.
METHODS
Total RNA was extracted from GC, ovaries, uteri, hearts (low rate of cell turnover) and livers (high rate of cell turnover) of prepubertal female mice. BH3-only Bcl-2 family members were cloned to make riboprobe. The expression patterns in the tissues evaluated by Northern blot analysis. Nix mRNA expression in ovarian granulosa cells after gonadotropin treatment also compared by Northern blot analysis.
RESULTS
Bad, Bid, Bim, Bmf, Map-1 and Nix were expressed in granulosa cells. Nix was most abundantly expressed in GC. In contrast, Blk was expressed in the ovary, liver, heart and uterus, but not in GC. Bmf, a sensor or microfilament disassembly, was expressed in GC, ovary and uterus, with limited to no expression in non-reproductive tissues. Nix mRNA expression was not regulated by gonadotropin after 42 hour.
CONCLUSION
These studies will help to complete a molecular blueprint of the regulatory network that controls GC death during follicular atresia. In addition, these data, which show a tissue/cell-selective profile of BH3-only expression, may also explain the known variation in the in vivo apoptotic response of different tissues/cells to generic stimuli that should be globally lethal.