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Estrus Synchronization and Ovarian Hyper Stimulation Treatments Have Negligible Effects on Cumulus Oocyte Complexes Gene Expression: Induction of Ovulation Causes Major Expression Changes

ABSTRACT: The effects of exogenous hormones used for estrus synchronization, and ovarian hyper stimulation on cumulus oocyte complexes (COCs) gene expression in sexually mature rats were determined using microarrays. Gene expression in COCs collected from GnRH (Gtrt), GnRH+eCG (G+Etrt), and GnRH+eCG+hCG (G+E+Htrt) treatments were compared to COCs from naturally cycling (NC) rats. There was no significant difference in gene expression among NC, Gtrt and G+Etrt. Over 2600 genes were significantly different between NC and G+E+Htrt (P<0.05). Genes encoding proteins that are involved in prostaglandin synthesis (Ptgs2, Pla2g4a, Runx1); cholesterol biosynthesis (Hmgcr, Sc4mol, Dhcr24); receptors that allow cholesterol uptake (Ldlr, Scarb1); regulate progesterone synthesis (Star); inactivate estrogen (Sult1e1); and downstream effectors of LH signal (Pgr, Cebpb, Creb3l1, Areg, Ereg, Adamts1) were upregulated in G+E+Htrt. Genes encoding proteins that are involved in DNA replication (Ccne2, Orc5l, Rad50, Mcm6); reproductive developmental process and granulosa cell expansion (Gdf9, Bmp15, Amh, Amhr2, Bmpr1b, Tgfb2, Foxl2, Pde3a, Esr2, Fshr, Ybx2, Ccnd2, Ccnb1ip1, Zp3); maternal effect genes that are important for embryo development (Zar1, Npm2, Nlrp5, Dnmt1, H1foo, Zfp57); amino acid degradation and ketogenesis (Hmgcs2 , Cpt1b) were downregulated in G+E+Htrt. These results on rat model show that hormones used for estrus synchronization (Gtrt) and ovarian hyper stimulation (G+Etrt) had minimal effects on gene expression. However, induction of ovulation (G+E+Htrt) caused major changes in gene expression of rat COCs. This study provides comprehensive information about regulated genes during late follicle development and ovulation induction.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE41836 | GEO | 2013/02/01

SECONDARY ACCESSION(S): PRJNA178294

REPOSITORIES: GEO

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Project description:Gonadotropin surge acts on the preovulatory follicle of the ovary to induce luteinization of follicular cells, oocyte meiotic maturation, cumulus expansion and follicular rupture leading to ovulation. These processes are brought about by spatial and temporal changes in transcriptional regulation of genes in the follicular cells in response to the gonadotropin surge. Analysis of gene expression changes in the periovulatory follicular cells will help in delineating the signal transduction pathways involved in the above mentioned processes. In monoovulatory species like bovines, the time interval of 24-28 hours between gonadotropin surge and ovulation provides distinct advantage for studying the temporal changes in the gene expression pattern. Thus, in the present study, we attempt to identify the temporal changes in the global gene expression profile in the periovulatory follicle of buffalo cows in response to gonadotropin surge and the results suggest the involvement of Insulin-like Growth Factor 1 and cytokine signaling pathways in the periovulatory events. Experiment Overall Design: To study the periovulatory gene expression changes in buffalo cows, an induced-ovulation model system involving sequential treatment with PGF2alpha and GnRH was standardized. The follicular wave containing at least one large follicle of ~7mm size was determined by ultrasonography on day 7 of the estrous cycle before administering exogenous PGF2alpha to induce luteolysis and follicular growth. Exogenous GnRH (100Âµg i.m) was administered 36h post PGF2alpha to induce LH surge. The time course of increase in LH levels post GnRH injection was monitored. Since peak LH levels are attained 2 h post GnRH administration, the time intervals of 3 h post GnRH (corresponding to1 h post LH surge) and 24 h post GnRH (corresponding to 22 h post LH surge) were chosen to identify the gene expression profile associated with immediate early and delayed changes in periovulatory follicle respectively. Thus ovaries were collected before, 1 h and 22 h post LH surge and follicle wall and granulosa cells were isolated from the ovaries and snap frozen for the purpose of RNA isolation.

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Estrus Synchronization and Ovarian Hyper Stimulation Treatments Have Negligible Effects on Cumulus Oocyte Complexes Gene Expression: Induction of Ovulation Causes Major Expression Changes

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