Germline competency of human embryonic stem cells depends on eomesodermin.

In humans, germline competency and the specification of primordial germ cells (PGCs) are thought to occur in a restricted developmental window during early embryogenesis. Despite the importance of specifying the appropriate number of PGCs for human reproduction, the molecular mechanisms governing PGC formation remain largely unexplored. Here, we compared PGC-like cell (PGCLC) differentiation from 18 independently derived human embryonic stem cell (hESC) lines, and discovered that the expression of primitive streak genes were positively associated with hESC germline competency. Furthermore, we show that chemical inhibition of TGFß and WNT signaling, which are required for primitive streak formation and CRISPR/Cas9 deletion of Eomesodermin (EOMES), significantly impacts PGCLC differentiation from hESCs. Taken together, our results suggest that human PGC formation involves signaling and transcriptional programs associated with somatic germ layer induction and expression of EOMES.

Reconstituted ovaries self-assemble without an ovarian surface epithelium.

Three-dimensional (3D) stem cell models of the ovary have the potential to benefit women's reproductive health research. One such model, the reconstituted ovary (rOvary) self-assembles with pluripotent stem cell-derived germ cells creating a 3D ovarian mimic competent to support the differentiation of functional oocytes inside follicles. In this study, we evaluated the cellular composition of the rOvary revealing the capacity to generate multiple follicles surrounded by NR2F2+ stroma cells. However, the rOvary does not develop a surface epithelium, the source of second-wave pre-granulosa cells, or steroidogenic theca. Therefore, the rOvary models represent the self-assembly of activated follicles in a pre-pubertal ovary poised but not yet competent for hormone production.

EED is required for mouse primordial germ cell differentiation in the embryonic gonad.

Development of primordial germ cells (PGCs) is required for reproduction. During PGC development in mammals, major epigenetic remodeling occurs, which is hypothesized to establish an epigenetic landscape for sex-specific germ cell differentiation and gametogenesis. In order to address the role of embryonic ectoderm development (EED) and histone 3 lysine 27 trimethylation (H3K27me3) in this process, we created an EED conditional knockout mouse and show that EED is essential for regulating the timing of sex-specific PGC differentiation in both ovaries and testes, as well as X chromosome dosage decompensation in testes. Integrating chromatin and whole genome bisulfite sequencing of epiblast and PGCs, we identified a poised repressive signature of H3K27me3/DNA methylation that we propose is established in the epiblast where EED and DNMT1 interact. Thus, EED joins DNMT1 in regulating the timing of sex-specific PGC differentiation during the critical window when the gonadal niche cells specialize into an ovary or testis.

Expansion of Luminal Progenitor Cells in the Aging Mouse and Human Prostate.

Aging is associated with loss of tissue mass and a decline in adult stem cell function in many tissues. In contrast, aging in the prostate is associated with growth-related diseases including benign prostatic hyperplasia (BPH). Surprisingly, the effects of aging on prostate epithelial cells have not been established. Here we find that organoid-forming progenitor activity of mouse prostate basal and luminal cells is maintained with age. This is caused by an age-related expansion of progenitor-like luminal cells that share features with human prostate luminal progenitor cells. The increase in luminal progenitor cells may contribute to greater risk for growth-related disease in the aging prostate. Importantly, we demonstrate expansion of human luminal progenitor cells in BPH. In summary, we define a Trop2+ luminal progenitor subset and identify an age-related shift in the luminal compartment of the mouse and human prostate epithelium.