Richman, H. E. | Search bioRxiv

bioRxiv2026

Acute Degradation of Pumilio Proteins Uncovers a Biphasic Post-transcriptional Regulatory Hierarchy Controlling Embryonic Stem Cell Fate Decisions

Post-transcriptional regulation is critical for mammalian embryogenesis yet has been underexplored. We previously showed that RNA-binding Pumilio proteins (Pum1/2) are essential for early mouse embryogenesis and embryonic stem cell (ESC) functions. Here, using acute protein degradation systems combined with time-resolved RNA-seq and eCLIP, we delineate a two-phase regulatory hierarchy modulated by Pum1/2 in mouse ESCs. The first phase, occurring within 10 hours of Pum1/2 depletion, is predominantly the stabilization of over 100 Pum1/2-target mRNAs, while the second phase, occurring in subsequent 66 hours, propagates to over 1,000 mRNAs mostly through indirect regulatory effects. Functionally, Pum1/2 depletion delays transition from naive to formative pluripotency, impairs neuroectoderm differentiation, and enhances germline specification. Mechanistically, Pum1/2 directly repress mRNAs encoding PRC2 subunits, including Suz12, thereby constraining H3K27me3 deposition at neuroectodermal gene loci. These findings establish Pum1/2 as biphasic post-transcriptional regulators of pluripotency and lineage balance and link RNA stability control to chromatin-mediated silencing. HIGHLIGHTSO_LIAcute Pum1/2 degradation provides temporal resolution for profiling post-transcriptional regulation. C_LIO_LIPum1/2 destabilize more than 100 direct targets and modulate a biphasic network of over 1,000 mRNAs. C_LIO_LIPum1/2 loss delays pluripotency transition, suppresses neuroectoderm, and promotes germline fate. C_LIO_LIPum1/2 directly regulate Suz12 mRNA decay to modulate PRC2-mediated repression. C_LI

cell biology↗

bioRxiv2025

Transcriptional Integration of Meiotic Prophase I Progression and Early Oocyte Differentiation

Female reproductive senescence results from the regulated depletion of a finite pool of oocytes called the ovarian reserve. This pool of oocytes is initially established during fetal development, but the oocytes that comprise it must remain quiescent for decades until they are activated during maturation in adulthood. In order for developmentally competent oocytes to populate the ovarian reserve they must successfully initiate both meiosis and oogenesis. As the factors that regulate the timing and fidelity of these early events remain elusive, we assessed the precise function and timing of the transcriptional regulator TAF4b during meiotic prophase I progression in mouse fetal oocytes. Compared to matched controls, E14.5 Taf4b-deficient oocytes enter meiosis I in a timely manner however, their subsequent progression through the pachytene-to-diplotene transition of meiotic prophase I is compromised. Moreover, this disruption of meiotic progression is associated with the reduced ability of Taf4b-deficient oocytes to repair double-strand DNA breaks. Transcriptional profiling of Taf4b-deficient oocytes reveals that between E16.5 and E18.5 these oocytes fail to coordinate the reduction of meiotic gene expression and the induction of oocyte differentiation genes. These studies reveal that TAF4b promotes the formation of the ovarian reserve in part by orchestrating the timely transition to meiosis I arrest and oocyte differentiation, which are often perceived as separate events.

genetics↗