Upon fertilization, drastic chromatin reorganization occurs during preimplantation development . However, the global chromatin landscape and its molecular dynamics in this period remain largely unexplored in humans. Here we investigate chromatin states in human preimplantation development using an improved assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) . We find widespread accessible chromatin regions in early human embryos that overlap extensively with putative cis-regulatory sequences and transposable elements. Integrative analyses show both conservation and divergence in regulatory circuitry between human and mouse early development, and between human pluripotency in vivo and human embryonic stem cells. In addition, we find widespread open chromatin regions before zygotic genome activation (ZGA). The accessible chromatin loci are readily found at CpG-rich promoters. Unexpectedly, many others reside in distal regions that overlap with DNA hypomethylated domains in human oocytes and are enriched for transcription factor-binding sites. A large portion of these regions then become inaccessible after ZGA in a transcription-dependent manner. Notably, such extensive chromatin reorganization during ZGA is conserved in mice and correlates with the reprogramming of the non-canonical histone mark H3K4me3, which is uniquely linked to genome silencing. Taken together, these data not only reveal a conserved principle that underlies the chromatin transition during mammalian ZGA, but also help to advance our understanding of epigenetic reprogramming during human early development and in vitro fertilization.
Context:Recently, two patients with primary ovarian insufficiency (POI) delivered healthy babies after in vitro activation (IVA) treatment followed by auto-transplantation of frozen-thawed ovarian tissues.Objective:This study sought to report the first case of live birth after IVA treatment following fresh ovarian tissue grafting in patients with POI, together with monitoring of follicle development and serum hormonal changes.Design:This was a prospective observational cohort study.Setting:We performed IVA treatment in 14 patients with POI with mean age of 29 years, mean duration since last menses of 3.8 years, and average basal FSH level of 94.5 mIU/mL.Interventions:Prior to IVA treatment, all patients received routine hormonal treatments with no follicle development. We removed one ovary from patients with POI and treated them with Akt stimulators. We improved upon early procedures by grafting back fresh tissues using a simplified protocol.Main Outcome Measures:In six of the 14 patients (43%), a total of 15 follicle development waves were detected, and four patients had successful oocyte retrieval to yield six oocytes. For two patients showing no spontaneous follicle growth, human menopausal gonadotropin treatment induced follicle growth at 6–8 months after grafting. After vitro fertilization of oocyte retrieved, four early embryos were derived. Following embryo transfer, one patient became pregnant and delivered a healthy baby boy, with three other embryos under cryopreservation.Conclusion:IVA technology can effectively activate residual follicles in some patients with POI and allow them to conceive their own genetic offspring. IVA may also be useful for treating patients with ovarian dysfunction including aging women and cancer survivors.
This work was supported by the National Natural Science Foundation of China (Grants 31271605 and 31471404), and the National Science Foundation for Young Scientists of China (Grant 31401274), and Science Foundation of First Affiliated Hospital of Zhengzhou University for Yong Scientists. The authors have declared that no competing interests exist.
The euploidy rates between the D5 and D6 blastocysts did not differ. High-quality D6 blastocysts in frozen-thawed cycles had similar developmental potential and pregnancy outcomes compared to those of high-quality D5 blastocysts. The quality of the blastocysts was an important factor that affected the pregnancy outcomes of the frozen-thawed cycles.
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