Chi, R.-p. A. | Search bioRxiv

bioRxiv2020

Identification of a Novel PP2A Regulator, WNK1, as Critical For Uterine Function

WNK1 is an atypical kinase protein ubiquitously expressed in humans and mice. A mutation in its encoding gene causes hypertension in humans which is associated with abnormal ion homeostasis. Our earlier findings demonstrated that WNK1 is critical for in vitro decidualization in human endometrial stromal cells – pointing towards an unrecognized role of WNK1 in female reproduction. Here, we employed a mouse model with conditional WNK1 ablation from the female reproductive tract to define its in vivo role in uterine biology. Loss of WNK1 altered uterine morphology, causing endometrial epithelial hyperplasia, adenomyosis and a delay in embryo implantation, ultimately resulting in compromised fertility. Combining transcriptomic, proteomic and interactomic analyses revealed a novel regulatory pathway whereby WNK1 represses AKT phosphorylation through the phosphatase PP2A in endometrial cells from both humans and mice. We show that WNK1 interacts with PPP2R1A, an isoform of the PP2A scaffold subunit. This interaction stabilizes the PP2A complex, which then dephosphorylates AKT. Therefore, loss of WNK1 reduced PP2A activity, causing AKT hypersignaling. Using FOXO1 as a readout of AKT activity, we demonstrate that there was escalated FOXO1 phosphorylation and nuclear exclusion, leading to a disruption in the regulation of genes that are crucial for embryo implantation.Competing Interest StatementThe authors have declared no competing interest.View Full Text

developmental biology↗

bioRxiv2019

Transcriptional and Progesterone Receptor Binding Profiles of the Human Endometrium Reveal Important Pathways and Regulators in the Epithelium During the Window of Implantation

ContextPoor uterine receptivity is one major factor leading to pregnancy loss and infertility. Understanding the molecular events governing successful implantation is hence critical in combating infertility.\n\nObjectiveTo define PGR-regulated molecular mechanisms and epithelial roles in receptivity.\n\nDesignRNA-seq and PGR-ChIP-seq were conducted in parallel to identify PGR-regulated pathways during the WOI in endometrium of fertile women.\n\nSettingEndometrial biopsies from the proliferative and mid-secretory phases were analyzed.\n\nPatients or Other ParticipantsParticipants were fertile, reproductive aged (18-37) women with normal cycle length; and without any history of dysmenorrhea, infertility, or irregular cycles. In total, 42 endometrial biopsies obtained from 42 women were analyzed in this study.\n\nInterventionsThere were no interventions during this study.\n\nMain Outcome MeasuresHere we measured the alterations in gene expression and PGR occupancy in the genome during the WOI, based on the hypothesis that PGR binds uterine chromatin cycle-dependently to regulate genes involved in uterine cell differentiation and function.\n\nResults653 genes were identified with regulated PGR binding and differential expression during the WOI. These were involved in regulating inflammatory response, xenobiotic metabolism, EMT, cell death, interleukin/STAT signaling, estrogen response, and MTORC1 response. Transcriptome of the epithelium identified 3,052 DEGs, of which 658 were uniquely regulated. Transcription factors IRF8 and MEF2C were found to be regulated in the epithelium during the WOI at the protein level, suggesting potentially important functions that are previously unrecognized.\n\nConclusionPGR binds the genomic regions of genes regulating critical processes in uterine receptivity and function.\n\nPrecisUsing a combination of RNA-seq and PGR ChIP-seq, novel signaling pathways and epithelial regulators were identified in the endometrium of fertile women during the window of implantation.

developmental biology↗