Divergent roles for KLF4 and TFCP2L1 in naive ground state pluripotency and human primordial germ cell development

Temporal and spatial staging of lung alveolar regeneration is determined by the grainyhead transcription factor Tfcp2l1

Alveolar epithelial type 2 (AT2) cells harbor the facultative progenitor capacity in the lung alveolus to drive regeneration after lung injury. Using single-cell transcriptomics, software-guided segmentation of tissue damage, and in vivo mouse lineage tracing, we identified the grainyhead transcription factor cellular promoter 2-like 1 (Tfcp2l1) as a regulator of this regenerative process. Tfcp2l1 loss in adult AT2 cells inhibits self-renewal and enhances AT2-AT1 differentiation during tissue regeneration. Conversely, Tfcp2l1 blunts the proliferative response to inflammatory signaling during the early acute injury phase. Tfcp2l1 temporally regulates AT2 self-renewal and differentiation in alveolar regions undergoing active regeneration. Single-cell transcriptomics and lineage tracing reveal that Tfcp2l1 regulates cell fate dynamics across the AT2-AT1 differentiation and restricts the inflammatory program in murine AT2 cells. Organoid modeling shows that Tfcp2l1 regulation of interleukin-1 (IL-1) receptor expression controlled these cell fate dynamics. These findings highlight the critical role Tfcp2l1 plays in balancing epithelial cell self-renewal and differentiation during alveolar regeneration.

iPSCs derived from infertile men carrying complex genetic abnormalities can generate primordial germ-like cells

Despite increasing insight into the genetics of infertility, the developmental disease processes remain unclear due to the lack of adequate experimental models. The advent of induced pluripotent stem cell (iPSC) technology has provided a unique tool for in vitro disease modeling enabling major advances in our understanding of developmental disease processes. We report the full characterization of complex genetic abnormalities in two infertile patients with either azoospermia or XX male syndrome and we identify genes of potential interest implicated in their infertility. Using the erythroblasts of both patients, we generated primed iPSCs and converted them into a naive-like pluripotent state. Naive-iPSCs were then differentiated into primordial germ-like cells (PGC-LCs). The expression of early PGC marker genes SOX17, CD-38, NANOS3, c-KIT, TFAP2C, and D2-40, confirmed progression towards the early germline stage. Our results demonstrate that iPSCs from two infertile patients with significant genetic abnormalities are capable of efficient production of PGCs. Such in vitro model of infertility will certainly help identifying causative factors leading to early germ cells development failure and provide a valuable tool to explore novel therapeutic strategies.

Human reproduction is regulated by retrotransposons derived from ancient Hominidae-specific viral infections

Germ cells are essential to pass DNA from one generation to the next. In human reproduction, germ cell development begins with the specification of primordial germ cells (PGCs) and a failure to specify PGCs leads to human infertility. Recent studies have revealed that the transcription factor network required for PGC specification has diverged in mammals, and this has a significant impact on our understanding of human reproduction. Here, we reveal that the Hominidae-specific Transposable Elements (TEs) LTR5Hs, may serve as TEENhancers (TE Embedded eNhancers) to facilitate PGC specification. LTR5Hs TEENhancers become transcriptionally active during PGC specification both in vivo and in vitro with epigenetic reprogramming leading to increased chromatin accessibility, localized DNA demethylation, enrichment of H3K27ac, and occupation of key hPGC transcription factors. Inactivation of LTR5Hs TEENhancers with KRAB mediated CRISPRi has a significant impact on germ cell specification. In summary, our data reveals the essential role of Hominidae-specific LTR5Hs TEENhancers in human germ cell development.

The transcription factor network required for primordial germ cell (PGC) specification is known to diverge in mammals. Here the authors show that hominidae-specific transposable element (TE) LTR5Hs becomes transcriptionally active during PGC specification, and LTR5Hs inactivation abrogates human PGC specification

The transcription factor Tfcp2l1 promotes primordial germ cell-like cell specification of pluripotent stem cells

Primordial germ cells (PGCs) are common ancestors of all germline cells. However, mechanistic understanding of how PGC specification occurs is limited. Here, we identified transcription factor CP2-like 1 (Tfcp2l1), an important pluripotency factor, as a pivotal factor for PGC-like cell (PGCLC) specification. High-throughput sequencing and quantitative real-time PCR analysis showed that Tfcp2l1 expression is gradually increased during mouse and human epiblast differentiation into PGCLCs in vivo and in vitro. Consequently, overexpression of Tfcp2l1 can enhance the specification efficiency even without inductive cytokines in mouse epiblast-like cells derived from embryonic stem cells, while knockdown of Tfcp2l1 significantly inhibits PGCLC generation. Mechanistic studies revealed that Tfcp2l1 exerts its function partially through the direct induction of PR domain zinc finger protein 14, a key PGC marker, as downregulation of the PR domain zinc finger protein 14 transcript can impair the ability of Tfcp2l1 to direct PGCLC commitment. Importantly, we finally demonstrated that the crucial role of the human homolog Tfcp2l1 in promoting PGCLC specification is conserved in human pluripotent stem cells. Together, our data uncover a novel function of Tfcp2l1 in PGCLC fate determination and facilitate a better understanding of germ cell development.