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Embryonic genome activation (EGA) is critical for embryonic development. However, our understanding of the regulatory mechanisms of human EGA is still incomplete. Human embryonic stem cells (hESCs) are an established model for studying developmental processes, but they resemble epiblast and are sub-optimal for modeling EGA. DUX4 regulates human EGA by inducing cleavage-stage-specific genes, while it also induces cell death. We report here that a short-pulsed expression of DUX4 in primed hESCs activates an EGA-like gene expression program in up to 17% of the cells, retaining cell viability. These DUX4-induced cells resembled eight-cell stage blastomeres and were named induced blastomere-like (iBM) cells. The iBM cells showed marked reduction of POU5F1 protein, as previously observed in mouse two-cell-like cells. Finally, the iBM cells were successfully enriched using an antibody against NaPi2b (SLC34A2), which is expressed in human blastomeres. The iBM cells provide an improved model system to study human EGA transcriptome.

Summary Actin has been linked to processes spanning the whole gene expression cascade, from regulating specific transcription factors, such as myocardin-related transcription factor, to chromatin remodeling and RNA polymerase function. However, whether actin controls the transcription of only specific genes or has a global role in gene expression has remained elusive. Our genome-wide analysis reveals, for the first time, that actin interacts with essentially all transcribed genes in Drosophila ovaries. Actin co-occupies the majority of gene promoters together with Pol II, and on highly expressed genes, these two proteins also associate with gene bodies. Mechanistically, actin is required for Pol II recruitment to gene bodies, and manipulation of nuclear transport factors for actin leads to the decreased expression of eggshell genes. Collectively, these results uncover a global role for actin in transcription and demonstrate the in vivo importance of balanced nucleocytoplasmic shuttling of actin in the transcriptional control of a developmental process., Graphical Abstract, Highlights • Genome-wide analysis shows actin on all transcribed genes • Actin binds with RNA polymerase II near transcription start sites of most genes • On highly expressed genes, actin is also found on the gene bodies • Nuclear transport of actin is required for transcription during fly development, Molecular Mechanism of Gene Regulation; Developmental Biology; Model Organism

Double homeobox 4 (DUX4) is expressed at the early pre-implantation stage in human embryos. Here we show that induced human DUX4 expression substantially alters the chromatin accessibility of non-coding DNA and activates thousands of newly identified transcribed enhance-like regions, preferentially located within ERVL-MaLR repeat elements. CRISPR activation of transcribed enhancers by C-terminal DUX4 motifs results in the increased expression of target embryonic genome activation (EGA) genes ZSCAN4 and KHDC1P1. We show that DUX4 is markedly enriched in human zygotes, followed by intense nuclear DUX4 localization preceding and coinciding Kith minor EGA. DUX4 knockdown in human zygotes led to changes in the EGA transcriptome but did not terminate the embryos. We also show that the DUX4 protein interacts with the Mediator complex via the C-terminal KIX binding motif. Our findings contribute to the understanding of DUX4 as a regulator of the non-coding genome.

The intestine is divided into functionally distinct regions along the anteroposterior (A/P) axis. How the regional identity influences the function of intestinal stem cells (ISCs) and their offspring remain largely unresolved. We introduce an imaging-based method, “Linear Analysis of Midgut” (LAM), which allows quantitative, regionally defined cellular phenotyping of the whole Drosophila midgut. LAM transforms image-derived cellular data from three-dimensional midguts into a linearized representation, binning it into segments along the A/P axis. Through automated multivariate determination of regional borders, LAM allows mapping and comparison of cellular features and frequencies with subregional resolution. Through the use of LAM, we quantify the distributions of ISCs, enteroblasts, and enteroendocrine cells in a steady-state midgut, and reveal unprecedented regional heterogeneity in the ISC response to a Drosophila model of colitis. Altogether, LAM is a powerful tool for organ-wide quantitative analysis of the regional heterogeneity of midgut cells.

Delayed puberty (DP) affects approximately 2% of adolescents. In the vast majority of patients in both sexes, it is due to constitutional delay of growth and puberty (CDGP), a self-limited condition in which puberty starts later than usual but progresses normally. However, some CDGP patients may benefit from medical intervention with low-dose sex steroids or peroral aromatase inhibitor letrozole (only for boys). Other causes of DP include permanent hypogonadotropic hypogonadism, functional hypogonadotropic hypogonadism (due to chronic diseases and conditions), and gonadal failure. In this review we discuss these themes along with the latest achievements in the field of puberty research, and include a brief synopsis on the differential diagnosis and management of patients with CDGP and congenital hypogonadotropic hypogonadism.