Explore the vast range of titles available.

Medulloblastoma (MB) comprises a group of heterogeneous paediatric embryonal neoplasms of the hindbrain with strong links to early development of the hindbrain 1 – 4 . Mutations that activate Sonic hedgehog signalling lead to Sonic hedgehog MB in the upper rhombic lip (RL) granule cell lineage 5 – 8 . By contrast, mutations that activate WNT signalling lead to WNT MB in the lower RL 9 , 10 . However, little is known about the more commonly occurring group 4 (G4) MB, which is thought to arise in the unipolar brush cell lineage 3 , 4 . Here we demonstrate that somatic mutations that cause G4 MB converge on the core binding factor alpha (CBFA) complex and mutually exclusive alterations that affect CBFA2T2 , CBFA2T3 , PRDM6 , UTX and OTX2 . CBFA2T2 is expressed early in the progenitor cells of the cerebellar RL subventricular zone in Homo sapiens , and G4 MB transcriptionally resembles these progenitors but are stalled in developmental time. Knockdown of OTX2 in model systems relieves this differentiation blockade, which allows MB cells to spontaneously proceed along normal developmental differentiation trajectories. The specific nature of the split human RL, which is destined to generate most of the neurons in the human brain, and its high level of susceptible EOMES + KI67 + unipolar brush cell progenitor cells probably predisposes our species to the development of G4 MB. Derailed differentiation of human-specific progenitors of the developing cerebellar rhombic lip is the cause of group 4 medulloblastoma, the most common childhood brain tumour. 

Medulloblastoma (MB) is the most common malignant brain tumor in children and among the subtypes, Group 3 MB has the worst outcome. Here, we perform an in vivo, patient-specific screen leading to the identification of Otx2 and c-MYC as strong Group 3 MB inducers. We validated our findings in human cerebellar organoids where Otx2/c-MYC give rise to MB-like organoids harboring a DNA methylation signature that clusters with human Group 3 tumors. Furthermore, we show that SMARCA4 is able to reduce Otx2/c-MYC tumorigenic activity in vivo and in human cerebellar organoids while SMARCA4 T910M, a mutant form found in human MB patients, inhibits the wild-type protein function. Finally, treatment with Tazemetostat, a EZH2-specific inhibitor, reduces Otx2/c-MYC tumorigenesis in ex vivo culture and human cerebellar organoids. In conclusion, human cerebellar organoids can be efficiently used to understand the role of genes found altered in cancer patients and represent a reliable tool for developing personalized therapies. Group 3 medulloblastoma (MB) is considered one of the most aggressive forms of this cancer. Here, the authors show that Otx2 and c-MYC oncogenes can drive Group 3 MB formation in mouse and human cerebellar organoids while SMARCA4 overexpression or a EZH2-specific inhibitor can inhibit tumorigenesis.

Early life stress increases risk for depression. Here we establish a “two-hit” stress model in mice wherein stress at a specific postnatal period increases susceptibility to adult social defeat stress and causes long-lasting transcriptional alterations that prime the ventral tegmental area (VTA)—a brain reward region—to be in a depression-like state. We identify a role for the developmental transcription factor orthodenticle homeobox 2 (Otx2) as an upstream mediator of these enduring effects. Transient juvenile—but not adult—knockdown of Otx2 in VTA mimics early life stress by increasing stress susceptibility, whereas its overexpression reverses the effects of early life stress. This work establishes a mechanism by which early life stress encodes lifelong susceptibility to stress via long-lasting transcriptional programming in VTA mediated by Otx2.

Recently, several studies using cultures of human embryos together with single-cell RNA-seq analyses have revealed differences between humans and mice, necessitating the study of human embryos 1 – 8 . Despite the importance of human embryology, ethical and legal restrictions have limited post-implantation-stage studies. Thus, recent efforts have focused on developing in vitro self-organizing models using human stem cells 9 – 17 . Here, we report genetic and non-genetic approaches to generate authentic hypoblast cells (naive hPSC-derived hypoblast-like cells (nHyCs))—known to give rise to one of the two extraembryonic tissues essential for embryonic development—from naive human pluripotent stem cells (hPSCs). Our nHyCs spontaneously assemble with naive hPSCs to form a three-dimensional bilaminar structure (bilaminoids) with a pro-amniotic-like cavity. In the presence of additional naive hPSC-derived analogues of the second extraembryonic tissue, the trophectoderm, the efficiency of bilaminoid formation increases from 20% to 40%, and the epiblast within the bilaminoids continues to develop in response to trophectoderm-secreted IL-6. Furthermore, we show that bilaminoids robustly recapitulate the patterning of the anterior–posterior axis and the formation of cells reflecting the pregastrula stage, the emergence of which can be shaped by genetically manipulating the DKK1/OTX2 hypoblast-like domain. We have therefore successfully modelled and identified the mechanisms by which the two extraembryonic tissues efficiently guide the stage-specific growth and progression of the epiblast as it establishes the post-implantation landmarks of human embryogenesis. Authentic hypoblast cells created from naive human pluripotent stem cells (hPSCs) spontaneously assemble with naive hPSCs to form a three-dimensional bilaminar structure (bilaminoids) with a pro-amniotic-like cavity.

The successful segregation of germ cells from somatic lineages is vital for sexual reproduction and species survival. In the mouse, primordial germ cells (PGCs), precursors of all germ cells, are induced from the post-implantation epiblast 1 . Induction requires BMP4 signalling to prospective PGCs 2 and the intrinsic action of PGC transcription factors 3 – 6 . However, the molecular mechanisms that connect BMP4 to induction of the PGC transcription factors that are responsible for segregating PGCs from somatic lineages are unknown. Here we show that the transcription factor OTX2 is a key regulator of these processes. Downregulation of Otx2 precedes the initiation of the PGC programme both in vitro and in vivo. Deletion of Otx2 in vitro markedly increases the efficiency of PGC-like cell differentiation and prolongs the period of PGC competence. In the absence of Otx2 activity, differentiation of PGC-like cells becomes independent of the otherwise essential cytokine signals, with germline entry initiating even in the absence of the PGC transcription factor BLIMP1. Deletion of Otx2 in vivo increases PGC numbers. These data demonstrate that OTX2 functions repressively upstream of PGC transcription factors, acting as a roadblock to limit entry of epiblast cells to the germline to a small window in space and time, thereby ensuring correct numerical segregation of germline cells from the soma. The transcription factor OTX2 ensures that germline induction is initially kept in check and only proceeds after OTX2 downregulation.

Transcription factor networks, together with histone modifications and signalling pathways, underlie the establishment and maintenance of gene regulatory architectures associated with the molecular identity of each cell type. However, how master transcription factors individually impact the epigenomic landscape and orchestrate the behaviour of regulatory networks under different environmental constraints is only partially understood. Here, we show that the transcription factor Nanog deploys multiple distinct mechanisms to enhance embryonic stem cell self-renewal. In the presence of LIF, which fosters self-renewal, Nanog rewires the pluripotency network by promoting chromatin accessibility and binding of other pluripotency factors to thousands of enhancers. In the absence of LIF, Nanog blocks differentiation by sustaining H3K27me3, a repressive histone mark, at developmental regulators. Among those, we show that the repression of Otx2 plays a preponderant role. Our results underscore the versatility of master transcription factors, such as Nanog, to globally influence gene regulation during developmental processes. Transcription factor (TF) networks are essential for the molecular identity of each cell type. Here, the authors show that TF Nanog utilises multiple molecular strategies to enhance embryonic stem cell self-renewal, which include regulation of chromatin accessibility in the presence of LIF or maintenance of H3K27me3 at developmental regulators in its absence.

The conversion of DNA 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) by TET enzymes represents a significant epigenetic modification, yet its role in early human embryos remains largely unknown. Here we showed that the early human embryo inherited a significant amount of 5hmCs from an oocyte, which unexpectedly underwent de novo hydroxymethylation during its growth. Furthermore, the generation of 5hmC in the paternal genome after fertilization roughly followed the maternal pattern, which was linked to DNA methylation dynamics and regions of sustained methylation. The 5hmCs persisted until the eight-cell stage and exhibited high enrichment at OTX2 binding sites, whereas knockdown of OTX2 in human embryos compromised the expression of early lineage genes. Specifically, the depletion of 5hmC affected the activation of embryonic genes, which was further evaluated by ectopically expressing mouse Tet3 in human early embryos. These findings revealed distinct dynamics of 5hmC and unravelled its multifaceted functions in early human embryonic development. Liang, Yan, Long, Ji et al. find that the origin and dynamics of 5-hydroxymethylcytosine (5hmC) during early development are not conserved between humans and mice and that 5hmC contributes to the activation of human embryonic genes.

Naive epiblast and embryonic stem cells (ESCs) give rise to all cells of adults. Such developmental plasticity is associated with genome hypomethylation. Here, we show that LIF–Stat3 signaling induces genomic hypomethylation via metabolic reconfiguration. Stat3 −/− ESCs show decreased α-ketoglutarate production from glutamine, leading to increased Dnmt3a and Dnmt3b expression and DNA methylation. Notably, genome methylation is dynamically controlled through modulation of α-ketoglutarate availability or Stat3 activation in mitochondria. Alpha-ketoglutarate links metabolism to the epigenome by reducing the expression of Otx2 and its targets Dnmt3a and Dnmt3b . Genetic inactivation of Otx2 or Dnmt3a and Dnmt3b results in genomic hypomethylation even in the absence of active LIF–Stat3. Stat3 −/− ESCs show increased methylation at imprinting control regions and altered expression of cognate transcripts. Single-cell analyses of Stat3 −/− embryos confirmed the dysregulated expression of Otx2 , Dnmt3a and Dnmt3b as well as imprinted genes. Several cancers display Stat3 overactivation and abnormal DNA methylation; therefore, the molecular module that we describe might be exploited under pathological conditions. Stat3 depletion in pluripotent cells decreases α-ketoglutarate and increases the expression of Otx2 and its targets Dnmt3a and Dnmt3b , leading to global DNA hypermethylation.

Zygotic genome activation is tightly associated with the modulation of chromatin accessibility via maternal transcription factors. Understanding how chromatin accessibility is established and identifying key maternal regulators are crucial to comprehending this process. Here, by developing CANTAC-seq, we generate a genome-wide map of accessible chromatin of early Xenopus tropicalis embryos and find that the open chromatin landscape is progressively established at cis -regulatory elements during zygotic genome activation. Based on the motif analysis and perturbation experiments, we demonstrate that E2f1 maintains a repressive chromatin environment and inhibits zygotic gene transcription before the mid-blastula transition. Moreover, we identify that Otx1, another maternal transcriptional activator, coordinates with E2f1 in regulating chromatin accessibility and zygotic genome activation. Together, E2f1 and Otx1 determine the timely expression of a subset of genes required for zygotic gene transcription and germ layer differentiation. Zygotic genome activation coincides with extensive chromatin remodeling coordinated by maternal transcription factors. Here, by mapping accessible chromatin during early embryonic development of Xenopus tropicalis , the authors show how maternal factors E2f1 and Otx1 work together to control zygotic genome activation.

Centralized nervous systems enable animals to detect environmental cues and coordinate behavior, but their evolutionary origins in deuterostomes remain unclear. Among deuterostomes, echinoderms—such as sea urchins—have long been thought to lack brain-like structures, especially in larval stages. Although recent gene expression and neural activity studies suggest brain-like properties in sea urchin larvae, direct links to behavior are still emerging. Here, we identify a light-sensitive cluster of neurons in the posterior neuroectoderm of sea urchin larvae. These neurons express UV-sensitive Opsin5 and regulatory genes such as rx , otx , six3 , and lhx6 , which are conserved in the vertebrate diencephalon. We mapped this domain using single-cell RNA sequencing and in situ hybridization. Knockdown of Opn5L impaired light-dependent swimming, indicating an active role in photoreception. While further work is needed to fully establish circuit-to-behavior relationships, our findings add to growing evidence that sea urchin larvae possess a non-visual photoreceptive neural center with molecular features shared by vertebrate brain regions. This suggests that such domains originated in the deuterostome ancestor and contributed to the early evolution of brain function. Here, they show that sea urchin larvae possess a non-visual, light-sensitive neural center with vertebrate-like molecular signatures, shedding light on the ancient origins of brain function in deuterostomes.