EMBO Reports最新文献

Most eukaryotes share core meiosis-specific genes, suggesting meiosis evolved once in the last eukaryotic common ancestor (LECA). These genes are master regulators of meiotic recombination, ensuring genetically diverse lineages. However, meiosis in organisms outside the animal, plant, and yeast lineages remains poorly understood. Core meiotic genes were recently identified in the model brown alga Ectocarpus but remain uncharacterised. Here, we combine bioinformatic, structural, and biochemical approaches to characterise the axial-element orthologues meiotic Ectocarpus HORMA-domain protein (ecHOP1) and its interactor reductional division protein 1 (ecRED1), providing insight into meiotic-recombination regulation in brown algae. We define the chromatin-binding region of ecHOP1 and show that it binds double-stranded DNA, and we find that Ectocarpus assembles its axial element using evolutionarily conserved principles in a unique combination. Our work lays a foundation for further studies of meiosis in brown algae and broadens understanding of the diversity and conservation of meiotic mechanisms.

Telomeres are essential for chromosome protection and genomic stability, and telomerase function is critical for organ homeostasis. Zebrafish is a useful vertebrate model for understanding cellular and molecular mechanisms of regeneration. The regeneration capacity of the caudal fin of wild-type zebrafish is not affected by repetitive amputation, but the behaviour of telomeres during this process has not yet been studied. Here, we characterize the regeneration process in a telomerase-deficient zebrafish model, and study the regenerative capacity after repetitive amputations at different ages. We find that the regenerative efficiency decreases with aging in all genotypes but telomere length is maintained even in telomerase-deficient fish. Our data indicate that telomere length can be maintained by the regenerating cells through the recombination-mediated Alternative Lengthening of Telomeres (ALT) pathway, which likely supports high rates of cell proliferation during the caudal fin regeneration process.

Naïve human embryonic stem cells (hESCs) possess some advantages over their primed counterparts, displaying distinctive metabolic and epigenetic properties. However, the master regulator governing these features remains unrecognized. Here, we systematically investigate functions of the core transcription factor NANOG in naïve hESCs. Acting as an upstream key regulator, NANOG directly activates genes associated with naïve pluripotency, acetyl-CoA synthesis and anti-oxidation in a naïve pluripotency state- dependent manner, and represses the expression of extraembryonic lineage genes in naïve hESCs. NANOG modulates transcription of multiple genes in various pathways of acetyl-CoA synthesis, maintains the intracellular acetyl-CoA level and characteristic epigenetic landscapes, particularly the high level of histone acetylation, in naïve hESCs. NANOG is indispensable for the high activity of both OXPHOS and glycolysis, a bivalent metabolic state typical in naïve hESCs. Furthermore, we identify GPX2 as a mediator of NANOG in sustaining redox balance and survival of naïve hESCs. Together, this study reveals previously unrecognized roles of NANOG in orchestrating transcriptional, metabolic and epigenetic signatures to secure human naïve pluripotency.

Batten disease is characterized by early-onset blindness, juvenile dementia and death within the second decade of life. The most common genetic cause are mutations in CLN3, encoding a lysosomal protein. Currently, no therapies targeting disease progression are available, largely because its molecular mechanisms remain poorly understood. To understand how CLN3 loss affects cellular signaling, we generated human CLN3 knock-out cells (CLN3-KO) and performed RNA-seq analysis. Our multi-dimensional analysis reveals the transcriptional regulator YAP1 as a key factor in remodeling the transcriptome in CLN3-KO cells. YAP1-mediated pro-apoptotic signaling is also increased as a consequence of CLN3 functional loss in retinal pigment epithelia cells, and in the hippocampus and thalamus of Cln3^Δ7/8 mice, an established model of Batten disease. Loss of CLN3 leads to DNA damage, activating the kinase c-Abl which phosphorylates YAP1, stimulating its pro-apoptotic signaling. This novel molecular mechanism underlying the loss of CLN3 in mammalian cells and tissues may pave a way for novel c-Abl-centric therapeutic strategies to target Batten disease.

Sexual dimorphism in neural wiring and behavior arises from both intrinsic genetic programs and environmental cues, yet how these factors interact to shape neuronal morphogenesis remains unclear. Here, we investigate sexually dimorphic collateral branching in PVP cholinergic interneurons of Caenorhabditis elegans. In hermaphrodites, PVP branches form near the vulva and exhibit dynamic morphologies enriched with synaptic proteins for dense core vesicles but not synaptic vesicles, suggesting a role in selective neuropeptide transmission. We find that sex identity is necessary but not sufficient for PVP branching. Sex identity engages autonomous insulin signaling via the FOXO transcription factor DAF-16 to promote branch formation and modulate dynamic branch morphologies according to nutritional status. However, external epithelial cues from primary vulval cells are both necessary and sufficient to induce branching independent of sex identity. Despite acting through distinct pathways, insulin signaling and vulval cues converge on F-actin cytoskeletal remodeling. These sexually dimorphic PVP branches modulate egg-laying behavior in hermaphrodites. Our study uncovers a multilayered regulatory framework integrating intrinsic sex-specific programs and extrinsic signaling to shape sexually dimorphic neural circuits.

Secretin is a gastrointestinal (GI) hormone that slows intestinal motility, an effect thought to be mediated through vagal afferent pathways. In this study we show evidence for a novel function of secretin involving a non-neural mechanism mediated by interstitial cells of Cajal (ICC). Transcripts of secretin receptors (Sctr) are expressed abundantly by ICC in the deep muscular plexus (ICC-DMP). Secretin inhibits small intestinal contractions in the presence of the neurotoxin, tetrodotoxin (TTX) and suppresses excitatory enteric neurotransmission. The inhibitory effects of secretin occur through inhibition of Ca²⁺ transients in ICC-DMP, likely via Gαs-coupled cAMP production and PKA activation that leads to inhibition of IP3 receptors. Our results provide a novel concept for the role of ICC-DMP in small intestinal motility. ICC-DMP serve as integration hubs in which signaling from the enteric nervous system and hormones converge and integrate regulatory responses controlling intestinal motility. In the case of secretin, integrated responses may serve to slow intestinal transit to enhance digestion and absorption of nutrients.

Early embryos often have unique chromatin states prior to zygotic genome activation (ZGA). In Drosophila, ZGA occurs after 13 reductive nuclear divisions during which the nuclear to cytoplasmic (N/C) ratio grows exponentially. Previous work found that histone H3 chromatin incorporation decreases while its variant H3.3 increases leading up to ZGA. In other cell types, H3.3 is associated with sites of active transcription and heterochromatin, suggesting a link between H3.3 and ZGA. Here, we test what factors regulate H3.3 incorporation at ZGA. We find that H3 nuclear availability falls more rapidly than H3.3 leading up to ZGA. We generate H3/H3.3 chimeric proteins at the endogenous H3.3 A locus and observe that chaperone binding, but not gene structure, regulates H3.3 behavior. We identify the N/C ratio as a major determinant of H3.3 incorporation. To isolate how the N/C ratio regulates H3.3 incorporation we test the roles of genomic content, zygotic transcription, and cell cycle state. We determine that cell cycle regulation, but not H3 availability or transcription, controls H3.3 incorporation. Overall, we propose that local N/C ratios control histone variant usage via cell cycle state during ZGA.

Primordial germ cells (PGCs) are the precursors of gametes, and the ability to derive PGC-like cells (PGCLCs) from pluripotent stem cells has transformed germline research. A key limitation remains producing PGCLCs in sufficient numbers for large-scale applications. Here, we show that overexpression of Nanog plus three PGC master regulators - Prdm1, Prdm14, and Tfap2c - in mouse epiblast-like cells and formative embryonic stem cells yields abundant and highly enriched PGCLCs without costly recombinant cytokines. Nanog enhances the PGC regulatory network, suppresses somatic differentiation, and stabilizes PGCLC fate. Transcriptomically, these PGCLCs are developmentally more advanced than cytokine-induced counterparts and can be sustained long-term or differentiated into spermatogonia-like cells. Using this platform, we conduct a CRISPRi screen of 701 epigenetic genes to identify those needed for PGCLC formation. Downregulation of Ncor2, a histone deacetylase (HDAC) recruiter, has the greatest impact. Additionally, the HDAC inhibitors valproic acid and sodium butyrate suppress PGCLC formation and sperm counts of in utero-exposed animals. This work establishes a scalable system for functional screening of genes that influence germline development.

Gastrulation is a fundamental developmental process during which germ layers are formed and the body axes are defined by the precise orchestration of cell movements and fate specification. Here, we identify the SOXE transcription factor Sox8 as a pivotal regulator of Xenopus laevis gastrulation. We show that Sox8 is expressed in the ventrolateral mesoderm, and that its depletion-via CRISPR-DiCas7-11-leads to blastopore closure defects and impaired AP axis elongation. Transcriptomic analysis reveals that Sox8 modulates Wnt signalling, in part by directly activating transcription of kremen2, a Wnt inhibitor. Indeed, chromatin immunoprecipitation confirms direct binding of Sox8 to the kremen2 promoter. Consequently, Sox8 or Kremen2 knockdown results in an abnormal ventral expansion of wnt11b mRNA that was consistent with increased nuclear β-catenin and reduced BMP signalling. These treatments also led to disruptions in axial and paraxial mesodermal patterning. Together, our data provide new insights into the molecular control of vertebrate gastrulation and invite researchers to assess whether this Sox8/Kremen2 regulatory axis is involved in other biological processes.

Notch signalling is a major signalling pathway coordinating cellular processes between neighbouring animal cells. In Drosophila, two E3 ubiquitin ligases, Neuralized (Neur) and Mindbomb1 (Mib1), regulate Notch ligand activation and are essential for development. However, the mammalian orthologs of Neur, Neuralized-like (NEURL) 1 and 1B, appear to be dispensable for development, as double knock-out mice show no overt developmental defects. Thus, it is unclear if and how NEURL proteins regulate the mammalian Notch ligands. To address this question, we examined NEURL proteins' ability to activate Notch ligands in a humanized Drosophila model and mammalian cell culture. We found that, unlike MIB1, NEURL proteins activate Notch only with a subset of mammalian ligands, which contain a Neuralized binding motif. This motif has the consensus sequence NxxN and is present only in Notch ligands DLL1 and JAG1, but not in DLL4 and JAG2. Thus, our results reveal a differential regulatory mechanism of Notch activation in mammals, which can potentially explain the limited role of NEURL proteins in mammalian development and homeostasis.