Isolation of Genes Differentially Expressed in Dominant and Subordinate Bovine Follicles

Abstract

In monoovulatory species such as cattle, unknown mechanisms lead to the selection of one of a cohort of developing ovarian follicles to assume dominance and continue to grow in each follicular wave. We have used suppressive subtraction hybridization to identify genes differentially expressed in the granulosa cells of dominant and subordinate follicles. Inhibin beta A, apolipoprotein E receptor 2, MAPK kinase kinase 5 (ask1), and carboxypeptidase D were isolated and verified to be reliable markers for dominant follicles using real-time RT-PCR. Before the time point at which dominant follicles can be distinguished by virtue of their deviation in size and growth rate, transcripts for inhibin beta A, apolipoprotein E receptor 2, and p450 aromatase were elevated specifically in the one to three largest follicles. On d 2.5 postovulation, near the time of dominant follicle selection, the mRNA expression profiles of MAPK kinase kinase 5 and carboxypeptidase D paralleled those of the other three genes, thus anticipating the clear molecular expression differences seen between the dominant follicle and the next largest follicle 1 d later. The functional relevance of elevated levels of these genes in the selection and maintenance of the dominant follicle is discussed.

The Expression Pattern of microRNAs in Granulosa Cells of Subordinate and Dominant Follicles during the Early Luteal Phase of the Bovine Estrous Cycle

“…Thus, it may be possible to imagine that the dominant and subordinate follicles have unique molecular signals that may affect differently the bidirectional crosstalk between the oocytes and the granulosa cells. Although, several authors [10]–[14] have described the presence of altered gene expression patterns in theca and/or granulosa cells of different follicular stages, the post transcriptional gene expression regulation mechanisms that lead the follicle to become dominant or subordinate are still unclear. Here we investigated accumulation or degradation of miRNAs in granulosa cells of subordinate and dominant follicles during the early luteal phase of the estrous cycle.…”

“…This may lead to the hypothesis that the follicular microenvironment could have unique molecular signals which would affect differently the bidirectional crosstalk between the oocytes and the companion somatic cells in the subordinate and dominant follicles. In this regard, several signaling molecules including the TGF-beta superfamily members, follicle stimulating hormone receptor, luteinizing hormone receptor, cytochrome 450s (CYP11A1, CYP17A1, CYP19A1) , GDF9, IGF-1, IGF-II, IGFBP2 and several of genes have been found to be altered in granulosa and/or theca cells depending on the size and stage of follicular development [10]–[14]. Abnormal expression of those developmentally related genes and gene products in the oocytes and supporting cells could then lead to cellular communication dysfunction and dysregulation of normal follicle recruitment and development [15].…”

Signaling by the Extracellular Matrix Protein Reelin Promotes Granulosa Cell Proliferation in the Chicken Follicle

“…Recent attempts to identify genes that regulate the selection and recruitment of follicles to develop into mature oocytes during the bovine estrous cycle by expression profiling led to the identification of ApoER2 as a candidate for such a function (10,11). In another study, ApoER2 has been shown to be preferentially expressed in bovine dominant follicles when compared with subordinate follicles (12). A splice variant of VLDLR, which is the major player in yolk uptake by the oocyte, is also expressed in chicken granulosa cells (13).…”

Development and Application of a Rat Ovarian Gene Expression Database

“…In the last decade, rapid progress has been made in discovering key players in these processes by using molecular techniques such as differential mRNA display (6,7), subtraction hybridization (8,9), ovarian cDNA library screening (10), and DNA microarray (11)(12)(13). Results from these pioneering studies have reinforced the belief that follicular development and ovulation are highly complex, tightly regulated processes that require numerous hormone-induced factors.…”