Maternal and embryonic signals cause functional differentiation of luminal epithelial cells and receptivity establishment.

Embryo implantation requires temporospatial maternal-embryonic dialog. Using single-cell RNA sequencing for the uterus from 2.5 to 4.5 days post-coitum (DPC) and bulk sequencing for the corresponding embryos of 3.5 and 4.0 DPC pregnant mice, we found that estrogen-responsive luminal epithelial cells (EECs) functionally differentiated into adhesive epithelial cells (AECs) and supporting epithelial cells (SECs), promoted by progesterone. Along with maternal signals, embryonic Pdgfa and Efna3/4 signaling activated AECs and SECs, respectively, enhancing the attachment of embryos to the endometrium and furthering embryo development. This differentiation process was largely conserved between humans and mice. Notably, the developmental defects of SOX9-positive human endometrial epithelial cells (similar to mouse EEC) were related to thin endometrium, whereas functional defects of SEC-similar unciliated epithelial cells were related to recurrent implantation failure (RIF). Our findings provide insights into endometrial luminal epithelial cell development directed by maternal and embryonic signaling, which is crucial for endometrial receptivity.

Biological and RNA regulatory function of MOV10 in mammalian germ cells.

BACKGROUND: RNA regulation by RNA-binding proteins (RBPs) involve extremely complicated mechanisms. MOV10 and MOV10L1 are two homologous RNA helicases implicated in distinct intracellular pathways. MOV10L1 participates specifically in Piwi-interacting RNA (piRNA) biogenesis and protects mouse male fertility. In contrast, the functional complexity of MOV10 remains incompletely understood, and its role in the mammalian germline is unknown. Here, we report a study of the biological and molecular functions of the RNA helicase MOV10 in mammalian male germ cells. RESULTS: MOV10 is a nucleocytoplasmic protein mainly expressed in spermatogonia. Knockdown and transplantation experiments show that MOV10 deficiency has a negative effect on spermatogonial progenitor cells (SPCs), limiting proliferation and in vivo repopulation capacity. This effect is concurrent with a global disturbance of RNA homeostasis and downregulation of factors critical for SPC proliferation and/or self-renewal. Unexpectedly, microRNA (miRNA) biogenesis is impaired due partially to decrease of miRNA primary transcript levels and/or retention of miRNA via splicing control. Genome-wide analysis of RNA targetome reveals that MOV10 binds preferentially to mRNAs with long 3'-UTR and also interacts with various non-coding RNA species including those in the nucleus. Intriguingly, nuclear MOV10 associates with an array of splicing factors, particularly with SRSF1, and its intronic binding sites tend to reside in proximity to splice sites. CONCLUSIONS: These data expand the landscape of MOV10 function and highlight a previously unidentified role initiated from the nucleus, suggesting that MOV10 is a versatile RBP involved in a broader RNA regulatory network.

Rapamycin-mediated mTOR inhibition impairs silencing of sex chromosomes and the pachytene piRNA pathway in the mouse testis.

Mechanistic target of rapamycin (mTOR) controls cell growth and metabolism in response to environmental and metabolic signals. Rapamycin robustly extends the lifespan in mammals and has clinical relevance in organ transplantation and cancer therapy but side effects include male infertility. Here, we report that chronic rapamycin treatment causes spermatogenic arrest in adult male mice due to defects in sex body formation and meiotic sex chromosome inactivation (MSCI). Many sex chromosome-linked genes were up-regulated in isolated pachytene spermatocytes from rapamycin-treated mice. RNA-Seq analysis also identified mRNAs encoding the core piRNA pathway components were decreased. Furthermore, rapamycin treatment was associated with a drastic reduction in pachytene piRNA populations. The inhibitory effects of rapamycin on spermatogenesis were partially reversible, with restoration of testis mass and sperm motility within 2 months of treatment cessation. Collectively, we have defined an essential role of mTOR in MSCI and identified a novel function as a regulator of small RNA homeostasis in male germ cells.

Differential regulation of spermatogenic process by Lkb1 isoforms in mouse testis.

Liver serine/threonine kinase B1 (LKB1) is a tumor suppressor associated with the pathogenesis of Peutz-Jeghers syndrome. Affected males are at increased risk of developing Sertoli cell tumors and display defective spermatogenesis. Male mice lacking the short isoform (Lkb1S) of Lkb1 were sterile and exhibited abnormal spermiogenesis. In addition to the short isoform, the long isoform of Lkb1 (Lkb1L) is also expressed in testis; however, the requirement of the long isoform for fertility and the functional difference between the isoforms remain unknown. Herein, different from the spermiation failure reported in Lkb1S knockout mice, conditional deletion (cKO) of both isoforms of Lkb1 in germ cells resulted in male sterility stemming from defects in acrosome formation, as well as nuclear elongation and condensation during spermatid differentiation. Additionally, cKO mice showed a progressive germ cell loss that was never reported in mice with Lkb1S deletion. Further experiments revealed that the defect resulted from the failure of spermatogonial stem/progenitor cells (SPCs) maintenance. Although increased mTORC1 activity in postnatal cKO testes was consistent with a tendency toward germline stem cell differentiation, in vivo inhibition of the pathway by rapamycin treatment failed to rescue the phenotype. Concurrently, we detected a significant reduction of mitochondrial activity in Lkb1deficient SPCs. The results suggest that the regulation of LKB1 on SPCs' maintenance is associated with mitochondrial functions but not through the mTOR signaling pathway. In summary, our study supports different roles of Lkb1 isoforms in spermatogenesis with Lkb1L directing SPCs maintenance, and Lkb1L and Lkb1S coordinately regulating spermatid differentiation.