Ufmylation regulates granulosa cell apoptosis via ER stress but not oxidative stress during goat follicular atresia.

Follicular atresia is primarily caused by granulosa cell (GC) apoptosis, although the mechanisms are largely unknown. Ufmylation is a recently identified ubiquitin-like post-translational modifier that plays an important role in cell proliferation and apoptosis. The purpose of this study was to investigate the effects of Ufmylation on GC apoptosis during goat follicular atresia. Ubiquitin-fold modifier 1 (UFM1) and its target DDRGK domain containing 1 (DDRGK1) proteins were identified in granulosa cells (GCs) isolated from all stages of preantral follicles and from healthy (HF), early atretic (EF) and progressed atretic (PF) antral follicles. The expression levels were higher in GCs derived from antral atretic follicles than healthy follicles. Although the viability of GCs was not affected after overexpression of UFM1, siRNA-mediated UFM1 silencing significantly inhibited GC proliferation and induced apoptosis. Notably, components of the ufmylation pathway were significantly upregulated in GCs induced by the ER stress agent tunicamycin (Tm) and thapsigargin (Tg), but not affected by oxidative stress inducer H2O2. Furthermore, UFM1 silencing markedly increased the apoptosis of GCs upon Tg treatment by stimulating the ER stress-related gene expression. Our results provide evidence that UFM1 and its target DDRGK1 are expressed in the goat GCs during follicular development and atresia, and ufmylation may play an important role in the prevention of ER stress but not oxidative stress-induced GCs apoptosis.