Sohlh2 inhibits the apoptosis of mouse primordial follicle oocytes via C-kit/PI3K/Akt/Foxo3a signalling pathway

Abstract We previously reported that bone morphogenetic protein 4/drosophila mothers against decapentaplegic protein (BMP4/Smad) signalling pathway initiated primordial follicle growth and prevented oocyte apoptosis via up-regulation of Sohlh2 and receptor for kit ligand (c-kit). The mechanism underlying this process was not fully elucidated. In the present study, primary oocyte cultures were established from ovaries of 3-day-old female mouse pups by two-step enzyme digestion. Cultures were divided into Sohlh2 small interference RNA (SiRNA) group, negative SiRNA group, Sohlh2 overexpression plasmid group and pCAG-puro group. TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labelling assay was carried out to detect the oocyte apoptosis; immunocytochemical staining and quantitative real time-polymerase chain reaction detected the expression of c-kit and Forkhead box O3a (Foxo3a); Western blot was performed to detect the expression of Sohlh2, C-kit, saerine/threonine kinases (Akt1) and Foxo3a. The results showed that Sohlh2 inhibited oocyte apoptosis and upregulated c-kit expression; Sohlh2 decreased the endonuclear Foxo3a via the upregulation of phosphorylated Akt1 (P-Akt1) and phosphorylated Foxo3a (P-Foxo3a) but not total Akt1 (T-Akt1) or total Foxo3a (T-Foxo3a); Sohlh2 increased P-Akt1 but not T-Akt1; the PI3K (phosphotidylinsitol-3-kinase) inhibitor LY294002 ameliorated the role of Sohlh2 on phosphorylation of Akt1 and Foxo3a. Sohlh2 may inhibit oocyte apoptosis via c-kit/PI3K/Akt/Foxo3a signalling pathway.