Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>Neurons are highly polarized cells that face the fundamental challenge of compartmentalizing a vast and diverse repertoire of proteins in order to function properly<jats:sup>1</jats:sup>. The axon initial segment (AIS) is a specialized domain that separates a neuron’s morphologically, biochemically and functionally distinct axon and dendrite compartments<jats:sup>2,3</jats:sup>. How the AIS maintains polarity between these compartments is not fully understood. Here we find that in <jats:italic>Caenorhabditis elegans</jats:italic>, mouse, rat and human neurons, dendritically and axonally polarized transmembrane proteins are recognized by endocytic machinery in the AIS, robustly endocytosed and targeted to late endosomes for degradation. Forcing receptor interaction with the AIS master organizer, ankyrinG, antagonizes receptor endocytosis in the AIS, causes receptor accumulation in the AIS, and leads to polarity deficits with subsequent morphological and behavioural defects. Therefore, endocytic removal of polarized receptors that diffuse into the AIS serves as a membrane-clearance mechanism that is likely to work in conjunction with the known AIS diffusion-barrier mechanism to maintain neuronal polarity on the plasma membrane. Our results reveal a conserved endocytic clearance mechanism in the AIS to maintain neuronal polarity by reinforcing axonal and dendritic compartment membrane boundaries.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Cellular function in tissue is dependent on the local environment, requiring new methods for spatial mapping of biomolecules and cells in the tissue context<jats:sup>1</jats:sup>. The emergence of spatial transcriptomics has enabled genome-scale gene expression mapping<jats:sup>2–5</jats:sup>, but the ability to capture spatial epigenetic information of tissue at the cellular level and genome scale is lacking. Here we describe a method for spatially resolved chromatin accessibility profiling of tissue sections using next-generation sequencing (spatial-ATAC-seq) by combining in situ Tn5 transposition chemistry<jats:sup>6</jats:sup> and microfluidic deterministic barcoding<jats:sup>5</jats:sup>. Profiling mouse embryos using spatial-ATAC-seq delineated tissue-region-specific epigenetic landscapes and identified gene regulators involved in the development of the central nervous system. Mapping the accessible genome in the mouse and human brain revealed the intricate arealization of brain regions. Applying spatial-ATAC-seq to tonsil tissue resolved the spatially distinct organization of immune cell types and states in lymphoid follicles and extrafollicular zones. This technology progresses spatial biology by enabling spatially resolved chromatin accessibility profiling to improve our understanding of cell identity, cell state and cell fate decision in relation to epigenetic underpinnings in development and disease.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Compelling evidence shows that brown and beige adipose tissue are protective against metabolic diseases<jats:sup>1,2</jats:sup>. PR domain-containing 16 (PRDM16) is a dominant activator of the biogenesis of beige adipocytes by forming a complex with transcriptional and epigenetic factors and is therefore an attractive target for improving metabolic health<jats:sup>3–8</jats:sup>. However, a lack of knowledge surrounding the regulation of PRDM16 protein expression hampered us from selectively targeting this transcriptional pathway. Here we identify CUL2–APPBP2 as the ubiquitin E3 ligase that determines PRDM16 protein stability by catalysing its polyubiquitination. Inhibition of CUL2–APPBP2 sufficiently extended the half-life of PRDM16 protein and promoted beige adipocyte biogenesis. By contrast, elevated CUL2–APPBP2 expression was found in aged adipose tissues and repressed adipocyte thermogenesis by degrading PRDM16 protein. Importantly, extended PRDM16 protein stability by adipocyte-specific deletion of CUL2–APPBP2 counteracted diet-induced obesity, glucose intolerance, insulin resistance and dyslipidaemia in mice. These results offer a cell-autonomous route to selectively activate the PRDM16 pathway in adipose tissues.</jats:p>

<jats:title>Abstract</jats:title><jats:p>A key event at the onset of development is the activation of a contractile actomyosin cortex during the oocyte-to-embryo transition<jats:sup>1–3</jats:sup>. Here we report on the discovery that, in <jats:italic>Caenorhabditis elegans</jats:italic> oocytes, actomyosin cortex activation is supported by the emergence of thousands of short-lived protein condensates rich in F-actin, N-WASP and the ARP2/3 complex<jats:sup>4–8</jats:sup> that form an active micro-emulsion. A phase portrait analysis of the dynamics of individual cortical condensates reveals that condensates initially grow and then transition to disassembly before dissolving completely. We find that, in contrast to condensate growth through diffusion<jats:sup>9</jats:sup>, the growth dynamics of cortical condensates are chemically driven. Notably, the associated chemical reactions obey mass action kinetics that govern both composition and size. We suggest that the resultant condensate dynamic instability<jats:sup>10</jats:sup> suppresses coarsening of the active micro-emulsion<jats:sup>11</jats:sup>, ensures reaction kinetics that are independent of condensate size and prevents runaway F-actin nucleation during the formation of the first cortical actin meshwork.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Cellular RNAs are heterogeneous with respect to their alternative processing and secondary structures, but the functional importance of this complexity is still poorly understood. A set of alternatively processed antisense non-coding transcripts, which are collectively called <jats:italic>COOLAIR</jats:italic>, are generated at the <jats:italic>Arabidopsis</jats:italic> floral-repressor locus <jats:italic>FLOWERING LOCUS C</jats:italic> (<jats:italic>FLC</jats:italic>)<jats:sup>1</jats:sup>. Different isoforms of <jats:italic>COOLAIR</jats:italic> influence <jats:italic>FLC</jats:italic> transcriptional output in warm and cold conditions<jats:sup>2–7</jats:sup>. Here, to further investigate the function of <jats:italic>COOLAIR</jats:italic>, we developed an RNA structure-profiling method to determine the in vivo structure of single RNA molecules rather than the RNA population average. This revealed that individual isoforms of the <jats:italic>COOLAIR</jats:italic> transcript adopt multiple structures with different conformational dynamics. The major distally polyadenylated <jats:italic>COOLAIR</jats:italic> isoform in warm conditions adopts three predominant structural conformations, the proportions and conformations of which change after cold exposure. An alternatively spliced, strongly cold-upregulated distal <jats:italic>COOLAIR</jats:italic> isoform<jats:sup>6</jats:sup> shows high structural diversity, in contrast to proximally polyadenylated <jats:italic>COOLAIR</jats:italic>. A hyper-variable <jats:italic>COOLAIR</jats:italic> structural element was identified that was complementary to the <jats:italic>FLC</jats:italic> transcription start site. Mutations altering the structure of this region changed <jats:italic>FLC</jats:italic> expression and flowering time, consistent with an important regulatory role of the <jats:italic>COOLAIR</jats:italic> structure in <jats:italic>FLC</jats:italic> transcription. Our work demonstrates that isoforms of non-coding RNA transcripts adopt multiple distinct and functionally relevant structural conformations, which change in abundance and shape in response to external conditions.</jats:p>