Retinoic acid enhances progesterone production via the cAMP/PKA signaling pathway in immature rat granulosa cells

Effect of Upregulation of Transcription Factor TFDP1 Binding Promoter Activity Due to RBP4 g.36491960G>C Mutation on the Proliferation of Goat Granulosa Cells

Retinol-binding protein 4 (RBP4), a member of the lipocalin family, is a specific carrier of retinol (vitamin A) in the blood. Numerous studies have shown that RBP4 plays an important role in mammalian embryonic development and that mutations in RBP4 can be used for the marker-assisted selection of animal reproductive traits. However, there are few studies on the regulation of reproduction and high-prolificacy traits by RBP4 in goats. In this study, the 5′ flanking sequence of RBP4 was amplified, and a G>C polymorphism in the promoter region -211 bp (g.36491960) was detected. An association analysis revealed that the respective first, second and third kidding number and mean kidding number of nanny goats with CC and GC genotypes (2.167 ± 0.085, 2.341 ± 0.104, 2.529 ± 0.107 and 2.189 ± 0.070 for CC and 2.052 ± 0.047, 2.206 ± 0.057, 2.341 ± 0.056 and 2.160 ± 0.039 for GC) were significantly higher (p < 0.05) than those with the GG genotype (1.893 ± 0.051, 2.027 ± 0.064, 2.107 ± 0.061 and 1.74 ± 0.05). The luciferase assay showed that luciferase activity was increased in C allele individuals compared with that in G allele individuals. A competitive electrophoretic mobility shift assay (EMSA) showed that individuals with the CC genotype had a stronger promoter region binding capacity than those with the GG genotype. In addition, transcription factor prediction software showed that the RBP4 g.36491960G>C mutation added a novel binding site for transcription factor DP-1 (TFDP1). RT−qPCR results showed that the expression of TFDP1 was significantly higher in the high-prolificacy group than in the low-prolificacy group, and the expression of RBP4 was higher in both the CC and GC genotypes than that in the GG genotype. TFDP1 overexpression significantly increased the expression of RBP4 mRNA (p < 0.05) and the expression of the cell proliferation factors cyclin-D1, cyclin-D2 and CDK4 (p < 0.05). The opposite trend was observed after interference with TFDP1. Both the EdU and CCK-8 results showed that TFDP1 expression could regulate the proliferation of goat ovarian granulosa cells. In summary, our results showed that RBP4 g.36491960G>C was significantly associated with fecundity traits in goats. The g.36491960G>C mutation enhanced the transcriptional activity of RBP4 and increased the expression of RBP4, thus improving the fertility of Yunshang black goats.

Long Non-coding RNA Maternally Expressed 3 Increases the Expression of Neuron-Specific Genes by Targeting miR-128-3p in All-Trans Retinoic Acid-Induced Neurogenic Differentiation From Amniotic Epithelial Cells

MicroRNA (miR)-128-3p is a brain-enriched miRNA that participates in the regulation of neural cell differentiation and the protection of neurons, but the mechanisms by which miR-128-3p regulates its target and downstream genes to influence cell fate from adult stem cells are poorly understood. In this study, we show down-regulation of miR-128-3p during all-trans retinoic acid (ATRA)-induced neurogenic differentiation from amniotic epithelial cells (AECs). We investigated miR-128-3p in both the Notch pathway and in the expression of neuron-specific genes predicted to be involved in miR-128-3p signaling to elucidate its role in the genetic regulation of downstream neurogenic differentiation. Our results demonstrate that miR-128-3p is a negative regulator for the transcription of the neuron-specific genes β III-tubulin, neuron-specific enolase (NSE), and polysialic acid-neural cell adhesion molecule (PSA-NCAM) via targeting Jagged 1 to inhibit activation of the Notch signaling pathway. We also used bioinformatics algorithms to screen for miR-128-3p interactions with long non-coding (lnc) RNA and circular RNA as competing endogenous RNAs to further elucidate underlying down-regulated molecular mechanisms. The lncRNA maternally expressed 3 is up-regulated by the ATRA/cAMP/CREB pathway, and it, in turn, is directly down-regulated by miR-128-3p to increase the amount of neuron differentiation. Endogenous miRNAs are, therefore, involved in neurogenic differentiation from AECs and should be considered during the development of effective cell transplant therapies for the treatment of neurodegenerative disease.

Retinoic Acid and Germ Cell Development in the Ovary and Testis

Retinoic acid (RA), a derivative of vitamin A, is critical for the production of oocytes and sperm in mammals. These gametes derive from primordial germ cells, which colonize the nascent gonad, and later undertake sexual differentiation to produce oocytes or sperm. During fetal development, germ cells in the ovary initiate meiosis in response to RA, whereas those in the testis do not yet initiate meiosis, as they are insulated from RA, and undergo cell cycle arrest. After birth, male germ cells resume proliferation and undergo a transition to spermatogonia, which are destined to develop into haploid spermatozoa via spermatogenesis. Recent findings indicate that RA levels change periodically in adult testes to direct not only meiotic initiation, but also other key developmental transitions to ensure that spermatogenesis is precisely organized for the prodigious output of sperm. This review focuses on how female and male germ cells develop in the ovary and testis, respectively, and the role of RA in this process.

Transcriptomic Analysis of Porcine Granulosa Cells Overexpressing Retinol Binding Protein 4

Retinol binding protein 4 (RBP4), mainly secreted by the liver and adipocytes, is a transporter of vitamin A. RBP4 has been shown to be involved in several pathophysiological processes, such as obesity, insulin resistance, and cardiovascular risk. Reports have indicated the high expression levels of RBP4 in cystic follicles. However, the role of RBP4 in mammalian follicular granulosa cells (GCs) remains largely unknown. To illustrate the molecular pathways associated with the effects of RBP4 on GCs, we used high-throughput sequencing to detect differential gene expression in GCs overexpressing RBP4. A total of 113 differentially expressed genes (DEGs) were identified in RBP4-overexpressing GCs, and they included 71 upregulated and 42 downregulated genes. The differential expressions of the top 10 DEGs were further confirmed by real-time quantitative polymerase chain reaction. Pathway analysis indicated that the DEGs are mostly involved in oxidative phosphorylation, Parkinson’s disease, non-alcoholic fatty liver disease, Huntington’s disease, cardiac muscle contraction, Alzheimer’s disease, fatty acid biosynthesis, AMP-activated protein kinase signaling pathway, and insulin signaling pathway. Genes in these pathways should be useful for future studies on GCs. Altogether, the results of our study establish a framework for understanding the potential functions of RBP4 in porcine GCs.

Molecular mechanism of mercuric chloride inhibiting progesterone secretion in ovarian granulosa cells of laying hens

This study investigated the effect of mercury (Hg) on progesterone secretion in ovarian granulosa cells of laying hens. The gene expressions of steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage (P450scc) and 3β-hydroxysteroid dehydrogenase (3β-HSD), cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway and intracellular calcium ion (Ca²⁺ ) were further investigated to uncover the molecular mechanism. Results revealed that the cell viability was gradually decreased after Hg exposure from 0 to 24 hr. Besides, progesterone secretion was significantly decreased (p < 0.05) as the concentration of Hg increased from 0 to 4 μM followed by a plateau in 6 μM Hg group at 12-hr time point. Compared with 0 μM Hg group, 4 and 6 μM Hg for 48 hr had significantly decreased progesterone secretion (p < 0.05), while Hg exposure for 6 and 24 hr had no apparent effect on progesterone secretion. In addition, positive correlations occurred among intracellular progesterone, cAMP, PKA, mRNA expressions of StAR, P450scc and 3β-HSD at 12-h and 24-h time points. On the contrary, intracellular Ca²⁺ level was negatively related to cAMP level at 6 time point and was negatively correlated with progesterone and PKA level at 48 time point. It could be concluded that Hg dose- and time-dependently inhibited progesterone secretion by means of attenuating cAMP-PKA signal pathway, gene expressions of StAR, P450scc and 3β-HSD and enhancing intracellular Ca²⁺ in ovarian granulosa cells of laying hens.