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Prolactin receptor signaling mediates beta-cell epigenetic adaptations to promote OVOL2-binding [scATAC-seq]

ABSTRACT: "Maternal pancreatic β-cells undergo functional and structural changes to adapt to increased metabolic demands during pregnancy. Lactogen signaling via the prolactin receptor (PRLR) contributes to these adaptations by increasing β-cell mass, insulin transcription and glucose-stimulated insulin secretion. Lactogen-responsive tissues such as the mammary glands and some hypothalamic nuclei display gestationally induced epigenetic changes, some of which persist long after birth. We have previously found that prolactin treatment in islets regulates the expression of epigenetic modifiers. However, whether lactogen signaling in β-cells mediates epigenetic changes to regulate chromatin accessibility has not been examined. Therefore, our objective was to determine whether PRLR signaling alters chromatin accessibility of β-cells to facilitate transcriptional regulation. We identified differentially accessible regions in wild type β-cells which had 718 overrepresented motifs following prolactin treatment of murine islets. Validating this approach, these included motifs bound by established PRLR signaling effectors such as the STAT family of transcription factors (TFs). Using RNA-sequencing we identified transcriptional changes in 41 TFs whose motifs were overrepresented in DARs. These TFs included several previously linked to PRLR signaling within β-cells, including Myc, Mafb and Esr1. Importantly, we also identified several TFs not previously associated with PRLR signaling, which included OVOL2 which is often associated with epigenetic regulation. OVOL2 is a transcription factor involved in EMT inhibition and energy homeostasis with unknown roles in β-cell functions. Here, we establish that OVOL2 acts as a negative regulator of PRL-dependent effects on glucose stimulated insulin secretion and β-cell proliferation, establishing a novel regulatory pathway for PRLR signaling.

ORGANISM(S): Mus musculus

PROVIDER: GSE319576 | GEO | 2026/04/01

REPOSITORIES: GEO

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Project description:ABSTRACT:Pregnancy requires a higher functional beta cell mass and this is associated with profound changes in the gene expression profile of pancreatic islets. Taking Tph1 as a sensitive marker for pregnancy-related islet mRNA expression in female mice, we previously identified prolactin receptors and placental lactogen as key signalling molecules. Since beta cells from male mice also express prolactin receptors, the question arose whether male and female islets have the same phenotypic resilience at the mRNA level during pregnancy. We addressed this question in vitro, by using islet tissue culture with placental lactogen and in vivo, by transplanting male or female islets into female acceptor mice. Additionally, the islet mRNA expression of pregnant prolactin receptor deficient mice was compared with that of their pregnant wild-type littermates. When cultured with placental lactogen, or transplanted in female recipients that became pregnant (day 12.5), male islets induced the ‘islet pregnancy gene signature’, which we defined as the 12 highest induced genes in non-transplanted female islets at day 12.5 of pregnancy. In addition, serotonin immunoreactivity was also induced in these male transplanted islets at day 12.5 of pregnancy. In order to investigate the importance of prolactin receptors in these mRNA changes we used a prolactin receptor deficient mouse model. For the 12 genes of the signature, which are highly induced in control pregnant mice, no significant induction of mRNA transcripts was found at day 9.5 of pregnancy. Together, our results support the key role of placental lactogen as a circulating factor that can trigger the pregnancy mRNA profile in male and female beta cells. The data obtained from the normal islets of pregnant mice (day12.5) was already described in Schraenen et al. 2010 (PMID: 20886204 and PMID: 20938637). Islets and islet grafts were isolated from non-prengant and pregnant mice for RNA extraction and hybridization on Affymetrix microarrays. For every condition, at least 3 biological replicates were used.

Project description:Primary hyperparathyroidism is a common endocrine disorder frequently affecting postmenopausal women. In this study we have investigated expression of the prolactin receptor (PRLr) in a panel of 37 sporadic parathyroid tumours, as well as functionality in vitro in cultured parathyroid tumour cells. High levels of the prolactin receptor gene (PRLR) transcripts were demonstrated in parathyroid tissues as compared to other reference tissues and breast cancer cells. PRLr products of 60/70 kDa were highly expressed in all parathyroid tumours. In addition varying levels of the 80 kDa PRLr isoform, with known proliferative activity, were demonstrated. In parathyroid tumours PRLr immunoreactivity was observed in cytoplasm in all cases and in addition in the plasma membrane (n = 12) or enlarged lysosomes (n = 4). In normal parathyroid rim PRLr was expressed in cytoplasm and granulae. In in vitro studies of short-term cultured human parathyroid tumour cells prolactin stimulation was associated with transcriptional changes in JAK/STAT, RIG-I like receptor and type II interferon signaling pathways as documented by gene expression profiling. Moreover, PRLR gene expression in parathyroid tumors was significantly inversely correlated with plasma total Ca2+ levels. In conclusion, the prolactin receptor was found highly abundant in human parathyroid gland, parathyroid tumours, correlated with patient Ca2+ levels and functionally responsive to physiological levels of prolactin. These findings suggest a role for the prolactin receptor in human parathyroid adenomas. Expression profiling was done in parathyroid adenomas subjected to prolactin treatment in culture. In addition, corresponding paraffin sections were obtained for verification of PRLr expression by immunohistochemistry. 200 mg/L prolactin (recombinant humanM-BM- prolactin, Cat. No. JM-4687-50, MBL Woburn, MA) was added to 1M-CM-^W 10^6 attached parathyroid tumour cells. Cells were harvested using RNAlater (QIAGEN) and homogenized with QIAshredder for RNA extraction after 3 h and 24 h in culture, respectively. Negative controls were collected in parallel with each case at the same time points. RNA was extracted using QIA Cube, and quality assessed with Bioanalyser and Nanodrop. Expression array profiling and data analysis was done at the KI core facility Bioinformatics and Expression Analysis (BEA, Novum, Huddinge) using the Affymetrix platform and the TITAN ST 1.1 array. A total of 16 samples were analysed including 4 parathyroid adenomas cultured for 3 h or 24 h in the presence of prolactin plus control samples cultured in parallel without prolactin.

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Prolactin receptor signaling mediates beta-cell epigenetic adaptations to promote OVOL2-binding [scATAC-seq]

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