A number of genes involved in zygotic genome activation (ZGA) have been identified, but the RNA‐binding maternal factors that are directly related to ZGA in mice remain unclear. The present study shows that maternal deletion of Igf  2bp2 (also commonly known as Imp2 ) in mouse embryos causes early embryonic developmental arrest in vitro at the 2‐cell‐stage. Transcriptomics and proteomics analyses of 2‐cell‐stage embryos in mice reveal that deletion of IMP2 downregulates the expression of Ccar1 and Rps14 , both of which are required for early embryonic developmental competence. IGF2, a target of IMP2, when added in culture media, increases the proportion of wild‐type embryos that develop successfully to the blastocyst stage: from 29% in untreated controls to 65% (50 × 10 ⁻⁹ m IGF2). Furthermore, in an experiment related to embryo transfer, foster mothers receiving IGF2‐treated embryos deliver more pups per female than females who receive untreated control embryos. In clinically derived human oocytes, the addition of IGF2 to the culture media significantly enhances the proportion of embryos that develop successfully. Collectively, the findings demonstrate that IMP2 is essential for the regulation and activation of genes known to be involved in ZGA and reveal the potential embryonic development‐related utility of IGF2 for animal biotechnology and for assisted reproduction in humans.

The histone modification writer Prdm9 has been shown to deposit H3K4me3 and H3K36me3 at future double-strand break (DSB) sites during the very early stages of meiosis, but the reader of these marks remains unclear. Here, we demonstrate that Zcwpw1 is an H3K4me3 reader that is required for DSB repair and synapsis in mouse testes. We generated H3K4me3 reader-dead Zcwpw1 mutant mice and found that their spermatocytes were arrested at the pachytene-like stage, which phenocopies theZcwpw1knock–out mice. Based on various ChIP-seq and immunofluorescence analyses using several mutants, we found that Zcwpw1's occupancy on chromatin is strongly promoted by the histone-modification activity of PRDM9. Zcwpw1 localizes to DMC1-labelled hotspots in a largely Prdm9-dependent manner, where it facilitates completion of synapsis by mediating the DSB repair process. In sum, our study demonstrates the function of ZCWPW1 that acts as part of the selection system for epigenetics-based recombination hotspots in mammals.

Context The high mobility group AT hook 2 (HMGA2) gene was previously identified in a genome-wide association study as a candidate risk gene that might be related to polycystic ovary syndrome (PCOS). Whether HMGA2 contributes to promoting granulosa cell (GC) proliferation in PCOS remains unknown. Objective We sought to determine whether HMGA2 is involved in the ovarian dysfunction of PCOS and in the mechanism of increased GC proliferation. Patients and Cells mRNA expression was analyzed in ovarian GCs from 96 women with PCOS and 58 healthy controls. Immortalized human GCs (KGN and SVOG cells) were used for the mechanism study. Main Outcome Measures mRNA expression in ovarian GCs was measured using quantitative RT-PCR, and KGN cells were cultured for proliferation assays after overexpression or knockdown of target genes. Protein expression analysis, luciferase assays, and RNA binding protein immunoprecipitation assays were used to confirm the mechanism study. Results HMGA2 and IGF2 mRNA binding protein 2 (IMP2) were highly expressed in the GCs of women with PCOS, and the HMGA2/IMP2 pathway promoted GC proliferation. Cyclin D2 and SERPINE1 mRNA binding protein 1 were regulated by IMP2 and were highly expressed in women with PCOS. Conclusions The HMGA2/IMP2 pathway was activated in women with PCOS and promoted the proliferation of GCs. This might provide new insights into the dysfunction of GCs in PCOS.

Meiosis is a specialized type of cell division that creates haploid germ cells and ensures their genetic diversity through homologous recombination. We show that the H3K4me3 reader ZCWPW1 is specifically required for meiosis prophase I progression in male but not in female germ cells in mice. Loss of Zcwpw1 in male mice caused a complete failure of synapsis, resulting in meiotic arrest at the zygotene to pachytene stage, accompanied by incomplete DNA double-strand break repair and lack of crossover formation, leading to male infertility. In oocytes, deletion of Zcwpw1 only somewhat slowed down meiosis prophase I progression; Zcwpw1^−/− oocytes were able to complete meiosis, and Zcwpw1^−/− female mice had normal fertility until mid-adulthood. We conclude that the H3K4me3 reader ZCWPW1 is indispensable for meiosis synapsis in males but is dispensable for females. Our results suggest that ZCWPW1 may represent a previously unknown, sex-dependent epigenetic regulator of germ cell meiosis in mammals.