EMBO Reports最新文献

During ovariogenesis, more than two-thirds of germ cells are sacrificed to improve the quality of the remaining oocytes. However, the detailed mechanisms behind this selection process are not fully understood in mammals. Here, we developed a high-resolution, four-dimensional ovariogenesis imaging system to track the progression of oocyte fate determination in live mouse ovaries. Through this, we identified a cyst-independent oocyte phagocytosis mechanism that plays a key role in determining oocyte survival. We found that oocytes act as individual cells, rather than connected cyst structures, during ovarian reserve construction. In this process, dominant oocytes capture and absorb cell debris from sacrificed oocytes to enrich their cytoplasm and support their survival. Single-cell sequencing indicated that the sacrificed oocytes are regulated by autophagy. When oocyte sacrifice was inhibited using autophagy inhibitors, the pool of surviving oocytes expanded, but they failed to fully develop and contribute to fertility. Our study suggests that mammals have evolved a cyst-independent selection system to improve oocyte quality, which is essential for sustaining a long reproductive lifespan.

During vertebrate neurogenesis, a transition from symmetric proliferative to asymmetric neurogenic divisions is critical to balance growth and differentiation. Using single-cell RNA-seq data from the chick embryonic neural tube, we identify the cell cycle regulator Cdkn1c as a key regulator of this transition. While Cdkn1 is classically associated with neuronal cell cycle exit, we show that its expression initiates at low levels in neurogenic progenitors. Functionally targeting the onset of this expression impacts the course of neurogenesis: Cdkn1c knockdown impairs neuron production by favoring proliferative symmetric divisions. Conversely, inducing a low-level Cdkn1c misexpression in self-expanding progenitors forces them to prematurely undergo neurogenic divisions. Cdkn1c exerts this effect primarily by inhibiting the CyclinD1-CDK4/6 complex and G1 phase lengthening. We propose that Cdkn1c acts as a dual driver of the neurogenic transition whose low level of expression first controls the progressive entry of progenitors into neurogenic modes of division before higher expression mediates cell cycle exit in daughter cells. This highlights that the precise control of neurogenesis regulators' expression sequentially imparts distinct functions essential for proper neural development.

Melanoma is a highly metastatic form of skin cancer for which current therapies offer limited benefits. We show here that the histone reader ATAD2 is overexpressed in melanoma and predicts poor prognosis, and that the MAP kinase pathway, via the transcription factor E2F1, stimulates ATAD2 expression. Genetic or pharmacological inhibition of ATAD2 suppresses the growth and metastasis of BRAF and NRAS mutant melanoma. Mechanistically, we show that ATAD2 inhibition activates both distinct and common tumor-suppressive pathways in BRAF and NRAS mutant melanoma. In particular, we find that ATAD2 inhibition induces ferroptosis in both contexts by downregulating the ferroptosis suppressor GPX4. The ferroptosis inducer erastin also inhibits melanoma growth. Combining the ATAD2 inhibitor BAY-850 with the MEK inhibitor trametinib potently suppresses melanoma growth. Our study identifies ATAD2 as a key driver of melanoma and provides a rationale for targeting ATAD2 in conjunction with the MAPK pathway to treat melanoma.

Hypoxia is both a physiological and pathological signal in cells. Changes in gene expression play a critical role in the cellular response to hypoxia, enabling cells to adapt to reduced oxygen availability. These changes are primarily mediated by the HIF family of transcription factors, however, other transcription factors such as NF-κB, are also activated by hypoxia. Although NF-κB is known to be activated by hypoxia, the extent to which NF-κB contributes to the hypoxic response remains poorly understood. Here, we analysed hypoxia-induced, NF-κB-dependent gene expression, to define the NF-κB-dependent hypoxic signature. Our analysis reveals that most genes downregulated by hypoxia require NF-κB for their repression. We show that although the NF-κB-mediated hypoxic response may vary between cell types, a core subset of hypoxia-inducible genes requires NF-κB across multiple cell backgrounds. We demonstrate that NF-κB is critical for reactive oxygen species (ROS) generation and regulation of genes involved in oxidative phosphorylation under hypoxia. This work highlights NF-κB's central role in the hypoxia response and offering new insights into gene expression regulation by hypoxia and NF-κB.

The brain's perineuronal extracellular matrix (ECM) is a crucial factor in maintaining the stability of mature brain circuitry. However, how activity-induced synaptic plasticity is achieved in the adult brain with a dense ECM is unclear. We hypothesized that neuronal activity induces cleavage of ECM, creating conditions for synaptic rearrangements. To test this hypothesis, we investigated neuronal activity-dependent proteolytic cleavage of brevican, a prototypical ECM proteoglycan, and the importance of this process for functional and structural synaptic plasticity in the rat hippocampus ex vivo. Our findings reveal that chemical long-term potentiation (cLTP) triggers rapid brevican cleavage in perisynaptic regions through the activation of an extracellular proteolytic cascade involving proprotein convertases and ADAMTS-4 and ADAMTS-5. This process requires NMDA receptor activation and involves astrocytes. Interfering with cLTP-induced brevican cleavage prevents the formation of new dendritic protrusions in CA1 but does not impact LTP induction by theta-burst stimulation of CA3-CA1 synapses. Our data reveal a mechanism of activity-dependent ECM remodeling and suggest that ECM degradation is essential for structural synaptic plasticity.

Argonautes are ancient proteins with well-characterised functions in cell-autonomous gene regulation and genome defence, but less clear roles in non-cell-autonomous processes. Extracellular Argonautes have been reported across plants, animals and protozoa, yet their biochemical and functional properties remain elusive. Here, we demonstrate that an extracellular Argonaute (exWAGO) released by the rodent-infective nematode Heligmosomoides bakeri is detectable inside mouse cells during the natural infection. We show that exWAGO is released from H. bakeri in both vesicular and non-vesicular forms that have different resistances to proteolysis, different accessibilities to antibodies and associate with different subsets of secondary siRNAs. Using recombinant exWAGO protein, we demonstrate that non-vesicular exWAGO is internalised by mouse cells in vitro and that immunisation of mice with exWAGO confers partial protection against subsequent H. bakeri infection and generates antibodies that block exWAGO uptake into cells. Finally, we show that properties of exWAGO are conserved across Clade V nematodes that infect humans and livestock. Together, this work expands the context in which Argonautes function and illuminates an RNA-binding protein as a vaccine target for parasitic nematodes.

Human immune protection against bacteria critically depends on activation of the complement system. The direct bacteriolytic activity of complement molecules against Gram-negative bacteria acts via the formation of Membrane Attack Complex (MAC) pores. Bactericidal MAC pores damage the bacterial outer membrane, leading to destabilization of the inner membrane. Although it is well-established that inner membrane damage is crucial for bacterial cell death, the critical event causing MAC-mediated inner membrane damage remains elusive. Here we question whether the bacterial cell envelope possesses vulnerable spots for MAC pores to insert. By following the localization of MAC pores on E. coli over time using fluorescence microscopy, we elucidate that MAC deposition initiates at the new bacterial pole, which induces inner membrane damage and halts bacterial division. MAC components C8 and C9 preferentially localize at new bacterial poles, while C3b localizes randomly on the bacterial surface. This suggests that preferential MAC localization is determined by one of the initial steps of MAC formation. These findings provide valuable information about the interplay between immune components and the Gram-negative cell envelope.