The gonadal niche safeguards human fetal germline cell development following maternal SARS-CoV-2 infection.

During pregnancy, germline development is vital for maintaining the continuation of species. Recent studies have shown increased pregnancy risks in COVID-19 patients at the perinatal stage. However, the potential consequence of infection for reproductive quality in developing fetuses remains unclear. Here, we analyze the transcriptome and DNA methylome of the fetal germline following maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We find that infection at early gestational age, a critical period of human primordial germ cell specification and epigenetic reprogramming, trivially affects fetal germ cell (FGC) development. Additionally, FGC-niche communications are not compromised by maternal infection. Strikingly, both general and SARS-CoV-2-specific immune pathways are greatly activated in gonadal niche cells to protect FGCs from maternal infection. Notably, there occurs an "in advance" development tendency in FGCs after maternal infection. Our study provides insights into the impacts of maternal SARS-CoV-2 infection on fetal germline development and serves as potential clinical guidance for future pandemics.

Chromatin landscape instructs precise transcription factor regulome during embryonic lineage specification.

Embryos, originating from fertilized eggs, undergo continuous cell division and differentiation, accompanied by dramatic changes in transcription, translation, and metabolism. Chromatin regulators, including transcription factors (TFs), play indispensable roles in regulating these processes. Recently, the trophoblast regulator TFAP2C was identified as crucial in initiating early cell fate decisions. However, Tfap2c transcripts persist in both the inner cell mass and trophectoderm of blastocysts, prompting inquiry into Tfap2c's function in post-lineage establishment. In this study, we delineate the dynamics of TFAP2C during the mouse peri-implantation stage and elucidate its collaboration with the key lineage regulators CDX2 and NANOG. Importantly, we propose that de novo formation of H3K9me3 in the extraembryonic ectoderm during implantation antagonizes TFAP2C binding to crucial developmental genes, thereby maintaining its lineage identity. Together, these results highlight the plasticity of the chromatin environment in designating the genomic binding of highly adaptable lineage-specific TFs and regulating embryonic cell fates.

Defining a TFAP2C-centered transcription factor network during murine peri-implantation.

Transcription factors (TFs) play important roles in early embryonic development, but factors regulating TF action, relationships in signaling cascade, genome-wide localizations, and impacts on cell fate transitions during this process have not been clearly elucidated. In this study, we used uliCUT&RUN-seq to delineate a TFAP2C-centered regulatory network, showing that it involves promoter-enhancer interactions and regulates TEAD4 and KLF5 function to mediate cell polarization. Notably, we found that maternal retinoic acid metabolism regulates TFAP2C expression and function by inducing the active demethylation of SINEs, indicating that the RARG-TFAP2C-TEAD4/KLF5 axis connects the maternal-to-zygotic transition to polarization. Moreover, we found that both genomic imprinting and SNP-transferred genetic information can influence TF positioning to regulate parental gene expressions in a sophisticated manner. In summary, we propose a ternary model of TF regulation in murine embryonic development with TFAP2C as the core element and metabolic, epigenetic, and genetic information as nodes connecting the pathways.

BMP4 preserves the developmental potential of mESCs through Ube2s- and Chmp4b-mediated chromosomal stability safeguarding.

Chemically defined medium is widely used for culturing mouse embryonic stem cells (mESCs), in which N2B27 works as a substitution for serum, and GSK3ß and MEK inhibitors (2i) help to promote ground-state pluripotency. However, recent studies suggested that MEKi might cause irreversible defects that compromise the developmental potential of mESCs. Here, we demonstrated the deficient bone morphogenetic protein (BMP) signal in the chemically defined condition is one of the main causes for the impaired pluripotency. Mechanistically, activating the BMP signal pathway by BMP4 could safeguard the chromosomal integrity and proliferation capacity of mESCs through regulating downstream targets Ube2s and Chmp4b. More importantly, BMP4 promotes a distinct in vivo developmental potential and a long-term pluripotency preservation. Besides, the pluripotent improvements driven by BMP4 are superior to those by attenuating MEK suppression. Taken together, our study shows appropriate activation of BMP signal is essential for regulating functional pluripotency and reveals that BMP4 should be applied in the serum-free culture system.