No abstract

Neonatal germ cell development provides the foundation of spermatogenesis. However, a systematic understanding of this process is still limited. To resolve cellular and molecular heterogeneity in this process, we profiled single cell transcriptomes of undifferentiated germ cells from neonatal mouse testes and employed unbiased clustering and pseudotime ordering analysis to assign cells to distinct cell states in the developmental continuum. We defined the unique transcriptional programs underlying migratory capacity, resting cellular states and apoptosis regulation in transitional gonocytes. We also identified a subpopulation of primitive spermatogonia marked by CD87 (plasminogen activator, urokinase receptor), which exhibited a higher level of self-renewal gene expression and migration potential. We further revealed a differentiation-primed state within the undifferentiated compartment, in which elevated Oct4 expression correlates with lower expression of self-renewal pathway factors, higher Rarg expression, and enhanced retinoic acid responsiveness. Lastly, a knockdown experiment revealed the role of Oct4 in the regulation of gene expression related to the MAPK pathway and cell adhesion, which may contribute to stem cell differentiation. Our study thus provides novel insights into cellular and molecular regulation during early germ cell development.

No abstract

Ten eleven translocation (Tet) family-mediated DNA oxidation on 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) represents a novel epigenetic modification that regulates dynamic gene expression during embryonic stem cells (ESCs) differentiation. Through the role of Tet on 5hmC regulation in stem cell development is relatively defined, how the Tet family is regulated and impacts on ESCs lineage development remains elusive. In this study, we show non-coding RNA regulation on Tet family may contribute to epigenetic regulation during ESCs differentiation, which is suggested by microRNA-29b (miR-29b) binding sites on the Tet1 3′ untranslated region (3′ UTR). We demonstrate miR-29b increases sharply after embyoid body (EB) formation, which causes Tet1 repression and reduction of cellular 5hmC level during ESCs differentiation. Importantly, we show this miR-29b/Tet1 regulatory axis promotes the mesendoderm lineage formation both in vitro and in vivo by inducing the Nodal signaling pathway and repressing the key target of the active demethylation pathway, Tdg. Taken together, our findings underscore the contribution of small non-coding RNA mediated regulation on DNA demethylation dynamics and the differential expressions of key mesendoderm regulators during ESCs lineage specification. MiR-29b could potentially be applied to enrich production of mesoderm and endoderm derivatives and be further differentiated into desired organ-specific cells.