Changes in Ovulation-Related Gene Expression during Induced Ovulation in the Amur Sturgeon (Acipenser schrenckii) Ovarian Follicles

Abstract

The luteinizing hormone (LH) and maturation-inducing steroids (MIS), such as 17α,20β-dihydroxy-4-pregnen-3-one, regulate the final oocyte maturation in teleosts. Oocyte maturational competence (OMC) and ovulatory competence measure the sensitivity to MIS for oocyte maturation and ovulation, respectively. However, the molecular mechanisms underlying the acquisition of ovulatory competence remain unknown. Sturgeons are an excellent research model for investigating these mechanisms. We examined the seasonal profiles of OMC and ovulatory competence in vitro and the expression of 17 ovulation-related gene candidates using quantitative PCR in Amur sturgeon ovarian follicles. The ovulatory competence was induced by the LH-releasing hormone analog (LHRHa) priming injection after acquiring the OMC, which was spontaneously induced in spring or autumn. Seven genes, including the tissue-type plasminogen activator (plat), were enhanced following the LHRHa priming injection in ovarian follicles sampled from anovulated and ovulated fish. The activin receptor type 1 (acvr1) and prostaglandin G/H synthase 2 (ptgs2) were only upregulated in ovulated fish. Our results suggest that plat/plasmin and prostaglandin (PG)/PG receptor systems are essential for sturgeon ovulation, similar to other vertebrates. Notably, successful ovulation depends on a sufficient PG synthesis, and mediators activating the PG/PG receptor system are essential for acquiring the ovulatory competence. We provide the first report of ovulation-related gene alterations in the ovarian follicles of Amur sturgeons.

Comparative proteomic analysis of the ovarian fluid and eggs of Siberian sturgeon

“…In addition to structural proteins, other ECM components, such as cathepsins (pro-cathepsin H (CTSH), dipeptidyl peptidase 1 (CTSC), and cathepsin D (CTSD)), PLG, matrix metalloproteinase-2 and 9 (MMP2, MMP9), and their metalloproteinase inhibitor 4 (TIMP4), are involved in follicular remodeling and the breakdown of the follicle wall during ovulation [ 41 – 43 ]. Recent studies also suggested the involvement of the plat/plasmin system in ECM remodeling during ovulation in sturgeon [ 44 ], which further supports the dynamic nature of the ECM in the sturgeon ovary. ECM proteins, such as myocilin (MYOC), thrombospondin-4 (THBS4), cadherin 13 (CDH13), leucine-rich repeat-containing protein 15 (LRRC15), and tetranectin (CLEC3B), may contribute to cell adhesion and signaling within the ovary in sturgeon.…”