Histone modifications regulate gene expression and development. To address how they are reprogrammed in human early development, we investigated key histone marks in human oocytes and early embryos. Unlike that in mouse oocytes, the permissive mark trimethylated histone H3 lysine 4 (H3K4me3) largely exhibits canonical patterns at promoters in human oocytes. After fertilization, prezygotic genome activation (pre-ZGA) embryos acquire permissive chromatin and widespread H3K4me3 in CpG-rich regulatory regions. By contrast, the repressive mark H3K27me3 undergoes global depletion. CpG-rich regulatory regions then resolve to either active or repressed states upon ZGA, followed by subsequent restoration of H3K27me3 at developmental genes. Finally, by combining chromatin and transcriptome maps, we revealed transcription circuitry and asymmetric H3K27me3 patterning during early lineage specification. Collectively, our data unveil a priming phase connecting human parental-to-zygotic epigenetic transition.

Background: The blastocyst morphology provided valuable roles for predicting pregnancy and live birth, but was still not fully understood for evaluating miscarriage. The aim of this study was to explore the association between blastocyst morphologic evaluation and first trimester miscarriage combined with karyotype of miscarried conceptus. Methods: This retrospective cohort study included a total of 2873 clinical pregnancy cycles with single blastocyst transfer performed from January 2013 to April 2019. Chromosome karyotype of miscarried conceptus was analyzed via single nucleotide polymorphism array analysis. Miscarriage and karyotype of miscarried conceptus associated with blastocyst morphology were analyzed by chi-square and logistic regression analysis. Results: A total of 354 (12.3%) cycles resulted in first trimester miscarriage. Miscarriage rates increased with trophectoderm (TE) grade from A to C (P = 0.012), while three morphologic parameters (blastocoele expansion degree, inner cell mass (ICM) and TE) showed no statistical significance with miscarriage after multivariable analysis. The rate of aneuploidy was 47.7% (83 of 174) in total miscarried conceptuses. For euploid miscarriages, the grade B of ICM occupied a higher proportion compared with aneuploidy, with OR of 2.474, (95% CI, 1.311-4.699), P = 0.005. Conclusions: Chromosomal aberration of embryo is an important genetic factor for first trimester miscarriage, and the quality of ICM is a potential indicator for euploid miscarriage. Blastocysts with grade A of ICM should be given priority during single blastocyst transfer to reduce potential miscarriage.

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Fetal growth restriction (FGR) is associated with multiple adverse perinatal outcomes, such as increased risk of intrauterine death, neonatal morbidity and mortality, and long-term adverse outcomes. Genetic etiological factors are critical in fetuses with intrauterine growth restriction, including chromosomal abnormalities, copy number variants, single gene disorders, uniparental disomy, epigenetic changes, and confined placental mosaicism. This paper aims to provide an overview of genetic defects related to FGR and to highlight the importance of prenatal genetic counseling and testing for precise diagnosis and management of FGR.