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The corpus luteum is an endocrine gland that synthesizes and secretes progesterone. Luteinizing hormone (LH) activates protein kinase A (PKA) signaling in luteal cells, increasing delivery of substrate to mitochondria for progesterone production. Mitochondria maintain a highly regulated equilibrium between fusion and fission in order to sustain biological function. Dynamin-related protein 1 (DRP1), is a key mediator of mitochondrial fission. The mechanism by which DRP1 is regulated in the ovary is largely unknown. We hypothesize that LH via PKA differentially regulates the phosphorylation of DRP1 on Ser616 and Ser637 in bovine luteal cells. In primary cultures of steroidogenic small luteal cells (SLCs), LH, and forskolin stimulated phosphorylation of DRP1 (Ser 637), and inhibited phosphorylation of DRP1 (Ser 616). Overexpression of a PKA inhibitor blocked the effects of LH and forskolin on DRP1 phosphorylation. In addition, LH decreased the association of DRP1 with the mitochondria. Genetic knockdown of the DRP1 mitochondria receptor, and a small molecule inhibitor of DRP1 increased basal and LH-induced progesterone production. Studies with a general Dynamin inhibitor and siRNA knockdown of DRP1 showed that DRP1 is required for optimal LH-induced progesterone biosynthesis. Taken together, the findings place DRP1 as an important target downstream of PKA in steroidogenic luteal cells.

2.AbstractEstablishment and maintenance of pregnancy is dependent on progesterone synthesized by luteal tissue in the ovary. Our objective was to identify the characteristics of lipid droplets (LDs) in ovarian steroidogenic cells. We hypothesized that LDs are a major feature of steroidogenic luteal cells and store cholesteryl esters. Bovine luteal tissue was used for whole tissue analysis. Further analyses were performed on isolated ovarian steroidogenic cells: granulosa and theca cells of the follicle, and small/large luteal cells. Isolated luteal LDs were collected for lipid/protein analyses. Luteal tissue contained perilipins 2/3/5, hormone-sensitive lipase and abhydrolase domain containing 5. Luteal tissue was enriched in TGs compared to other tissues, except of adipose tissue. Large and small luteal cells were distinguished from follicular cells by the presence of LDs and LD-associated proteins. Furthermore, LDs from large luteal cells were numerous and small; whereas, LDs from small luteal cells were large and less numerous. Isolated LDs contained nearly all of the TGs and cholesteryl esters present in luteal tissue. Isolated luteal LDs were composed primarily of TG, with lesser amounts of cholesteryl esters, diglyceride and other phospholipids. Bovine luteal tissue LDs are distinct from LDs in other bovine tissues, including follicular steroidogenic cells.

Affymetrix Bovine GeneChip® Gene 1.0 ST Array RNA expression analysis was performed on four somatic ovarian cell types: the granulosa cells (GCs) and theca cells (TCs) of the dominant follicle and the large luteal cells (LLCs) and small luteal cells (SLCs) of the corpus luteum. The normalized linear microarray data was deposited to the NCBI GEO repository (GSE83524). Subsequent ANOVA determined genes that were enriched (≥2 fold more) or decreased (≤−2 fold less) in one cell type compared to all three other cell types, and these analyzed and filtered datasets are presented as tables. Genes that were shared in enriched expression in both follicular cell types (GCs and TCs) or in both luteal cells types (LLCs and SLCs) are also reported in tables. The standard deviation of the analyzed array data in relation to the log of the expression values is shown as a figure. These data have been further analyzed and interpreted in the companion article “Gene expression profiling of ovarian follicular and luteal cells provides insight into cellular identities and functions” (Romereim et al., 2017) [1].

The corpus luteum (CL) is a transient endocrine gland that synthesizes and secretes the steroid hormone, progesterone. Progesterone biosynthesis is a complex process, converting cholesterol via a series of enzymatic reactions, into progesterone. Lipid droplets in luteal cells store cholesterol in the form of cholesterol esters, which can be utilized for steroidogenesis. In small luteal cells, luteinizing hormone (LH) increases intracellular cAMP concentrations leading to activation of protein kinase A (PKA), which phosphorylates downstream proteins, such as hormone sensitive lipase (HSL). Phosphorylation of HSL at Ser563 leads to increased HSL activation and association with lipid droplets, events which theoretically release cholesterol, which can be used for progesterone synthesis. Bovine CL were obtained from a local abattoir, dispersed, and luteal cells were enriched for SLC via centrifugal elutriation. Our results reveal that LH, forskolin, and cAMP induce HSL phosphorylation at Ser563and Ser660. Moreover, inhibiting HSL activity attenuates LH-induced P4 synthesis. Confocal analysis revealed that LH stimulates translocation of HSL to lipid droplets and mitochondria. Furthermore, LH increased trafficking of cholesterol from the lipid droplets to the mitochondria which was dependent on both PKA and HSL activation. These results demonstrate cholesterol stored in lipid droplets are utilized for LH-induced progesterone biosynthesis. Likewise, PKA-induced activation of HSL is required for release and trafficking of cholesterol from the lipid droplets to the mitochondria. Taken together, these findings support a role for a PKA/HSL signaling pathway in response to LH and demonstrate the dynamic relationship between PKA, HSL, and the lipid droplets in the synthesis of progesterone.HighlightsLH and PKA induce HSL phosphorylation at Ser563and Ser660HSL is required for optimal LH-induced P4 synthesisLH stimulates translocation of HSL to lipid droplets and mitochondriaLH stimulated trafficking of cholesterol from lipid droplets to mitochondria

In ruminants, prostaglandin F2alpha (PGF2α)-mediated luteolysis is essential prior to estrous cycle resumption, and is a target for improving fertility. To deduce early PGF2α-provoked changes in the corpus luteum a short time-course (0.5–4 h) was performed on cows at midcycle. A microarray-determined transcriptome was established and examined by bioinformatic pathway analysis. Classic PGF2α effects were evident by changes in early response genes (FOS, JUN, ATF3) and prediction of active pathways (PKC, MAPK). Several cytokine transcripts were elevated and NF-κB and STAT activation were predicted by pathway analysis. Self-organizing map analysis grouped differentially expressed transcripts into ten mRNA expression patterns indicative of temporal signaling cascades. Comparison with two analogous datasets revealed a conserved group of 124 transcripts similarly altered by PGF2α treatment, which both, directly and indirectly, indicated cytokine activation. Elevated levels of cytokine transcripts after PGF2α and predicted activation of cytokine pathways implicate inflammatory reactions early in PGF2α-mediated luteolysis.

Recent studies have suggested that chemokines may mediate the luteolytic action of prostaglandin F2α (PGF). Our objective was to identify chemokines induced by PGFin vivoand to determine the effects of interleukin 8 (IL8) on specific luteal cell typesin vitro. Mid-cycle cows were injected with saline or PGF, ovaries were removed after 0.5–4 h, and expression of chemokine was analyzed by qPCR.In vitroexpression of IL8 was analyzed after PGF administration and with cell signaling inhibitors to determine the mechanism of PGF-induced chemokine expression. Purified neutrophils were analyzed for migration and activation in response to IL8 and PGF. Purified luteal cell types (steroidogenic, endothelial, and fibroblast cells) were used to identify which cells respond to chemokines. Neutrophils and peripheral blood mononuclear cells (PBMCs) were cocultured with steroidogenic cells to determine their effect on progesterone production.IL8,CXCL2,CCL2, andCCL8transcripts were rapidly increased following PGF treatmentin vivo. The stimulatory action of PGF onIL8mRNA expressionin vitrowas prevented by inhibition of p38 and JNK signaling. IL8, but not PGF, TNF, or TGFB1, stimulated neutrophil migration. IL8 had no apparent action in purified luteal steroidogenic, endothelial, or fibroblast cells, but stimulated ERK phosphorylation in neutrophils. In coculture experiments neither IL8 nor activated neutrophils altered basal or LH-stimulated luteal cell progesterone synthesis. In contrast, activated PBMCs inhibited LH-stimulated progesterone synthesis from cultured luteal cells. These data implicate a complex cascade of events during luteolysis, involving chemokine signaling, neutrophil recruitment, and immune cell action within the corpus luteum.

This review focuses on recent advances in the understanding of metabolic processes used by the corpus luteum to control steroidogenesis and other cellular functions. The corpus luteum has abundant lipid droplets that are believed to store cholesteryl esters and triglycerides. Recent studies in other tissues indicate that cytoplasmic lipid droplets serve as platforms for cell signaling and interactions with other organelles. Lipid droplets are also critical organelles for controlling cellular metabolism. Emerging evidence demonstrates that LH via activation of the cAMP and the protein kinase A (PKA) signaling pathway stimulates the phosphorylation and activation of hormone-sensitive lipase (HSL), an enzyme that hydrolyzes cholesteryl esters stored in lipid droplets to provide cholesterol for steroidogenesis and fatty acids for utilization by mitochondria for energy production. The energy sensor AMP-activated protein kinase (AMPK) can inhibit steroidogenesis by interrupting metabolic pathways that provide cholesterol to the mitochondria or the expression of genes required for steroidogenesis. In addition to lipid droplets, autophagy also contributes to the regulation of the metabolic balance of the cell by eliminating damaged organelles and providing cells with essential nutrients during starvation. Autophagy in luteal cells is regulated by signaling pathways that impact AMPK activity and lipid droplet homeostasis. In summary, a number of signaling pathways converge on luteal lipid droplets to regulate steroidogenesis and metabolism. Knowledge of metabolic pathways in luteal cells is fundamental to understanding events that control the function and lifespan of the corpus luteum.

After ovulation, somatic cells of the ovarian follicle (theca and granulosa cells) become the small and large luteal cells of the corpus luteum. Aside from known cell type-specific receptors and steroidogenic enzymes, little is known about the differences in the gene expression profiles of these four cell types. Analysis of the RNA present in each bovine cell type using Affymetrix microarrays yielded new cell-specific genetic markers, functional insight into the behavior of each cell type via Gene Ontology Annotations and Ingenuity Pathway Analysis, and evidence of small and large luteal cell lineages using Principle Component Analysis. Enriched expression of select genes for each cell type was validated by qPCR. This expression analysis offers insight into cell-specific behaviors and the differentiation process that transforms somatic follicular cells into luteal cells.

Gonadotrophin-releasing hormone (GnRH) is a hypothalamic decapeptide with an undisputed role as a primary regulator of gonadal function. It exerts this regulation by controlling the release of gonadotrophins. However, it is becoming apparent that GnRH may have a variety of other vital roles in normal physiology. A reconsideration of the potential widespread action that this traditional reproductive hormone exerts may lead to the generation of novel therapies and provide insight into seemingly incongruent outcomes from current treatments using GnRH analogues to combat diseases such as prostate cancer.

Background Recently, the Bayesian method becomes more popular for analyzing high dimensional gene expression data as it allows us to borrow information across different genes and provides powerful estimators for evaluating gene expression levels. It is crucial to develop a simple but efficient gene selection algorithm for detecting differentially expressed (DE) genes based on the Bayesian estimators. Results In this paper, by extending the two-criterion idea of Chen et al. (Chen M-H, Ibrahim JG, Chi Y-Y. A new class of mixture models for differential gene expression in DNA microarray data. J Stat Plan Inference. 2008;138:387–404), we propose two new gene selection algorithms for general Bayesian models and name these new methods as the confident difference criterion methods. One is based on the standardized differences between two mean expression values among genes; the other adds the differences between two variances to it. The proposed confident difference criterion methods first evaluate the posterior probability of a gene having different gene expressions between competitive samples and then declare a gene to be DE if the posterior probability is large. The theoretical connection between the proposed first method based on the means and the Bayes factor approach proposed by Yu et al. (Yu F, Chen M-H, Kuo L. Detecting differentially expressed genes using alibrated Bayes factors. Statistica Sinica. 2008;18:783–802) is established under the normal-normal-model with equal variances between two samples. The empirical performance of the proposed methods is examined and compared to those of several existing methods via several simulations. The results from these simulation studies show that the proposed confident difference criterion methods outperform the existing methods when comparing gene expressions across different conditions for both microarray studies and sequence-based high-throughput studies. A real dataset is used to further demonstrate the proposed methodology. In the real data application, the confident difference criterion methods successfully identified more clinically important DE genes than the other methods. Conclusion The confident difference criterion method proposed in this paper provides a new efficient approach for both microarray studies and sequence-based high-throughput studies to identify differentially expressed genes. Electronic supplementary material The online version of this article (doi:10.1186/s12859-015-0664-3) contains supplementary material, which is available to authorized users.

Gonadotropin-releasing hormone (GnRH) is a decapeptide hypothalamic hormone that was named according to its first discovered function--at the head of the neuroendocrine reproductive axis. Numerous other organ systems express GnRH and/or its receptor, although a specific physiological role for GnRH outside of the reproductive axis has yet to be established. Several studies in lower vertebrates have reported GnRH and/or its receptor in the cerebellum. Here, we describe the presence of immunoreactive GnRH receptors in the Purkinje cells of the mammalian cerebellum for the first time. This study provides compelling anatomical evidence for a common link between the cerebellum and the hypothalamo-pituitary axis. Dysfunction of this link occurs in the rare genetic ataxia disorders--Gordon Holmes syndrome and Boucher-Neuhauser syndrome.