Biology subjects

Vazquez-Sanchez, S.

Publications and source records attributed to Vazquez-Sanchez, S..

9 recordsLinked to original sources

bioRxiv2025

Multimodal spatial transcriptomics determines repeat expansion, huntingtin aggregation, and selective cortical neuron loss in Huntington Disease

Huntingtons disease (HD) is caused by CAG expansion in HTT, yet how somatic repeat instability and huntingtin aggregation relate to selective cell loss in the human brain remains unclear. We have developed a multimodal spatial transcriptomics approach that enables defining transcriptional programs with subcellular resolution, somatic CAG repeat lengths, and six other pathology marks including huntingtin aggregates in every cell of intact brain sections. Imaging 428,173 cells in HD cortex revealed selective vulnerability: L5-6 NP and L6b deep-layer excitatory neurons undergo >50% loss, closely linked to very large (>380{+/-}55) somatic expansions. Intranuclear aggregation was most prevalent at intermediate somatic repeat expansion (220-300 CAGs) and was accompanied by broader transcriptional changes. In contrast, chandelier and somatostatin+ inhibitory interneurons are lost despite only modest repeat expansion or aggregation. These data provide a comprehensive resource and establish a broadly applicable framework for connecting repeat expansion and protein pathology across diverse cell types. Short Bullet pointsO_LIDevelopment of a novel, multimodal spatial transcriptomics platform enables definition of RNA transcriptomes with subcellular resolution, somatic repeat expansions, and protein accumulation in cells within tissue sections C_LIO_LIGeneration of two complementary datasets for HD and control cortex: 428,173 cells to quantify comprehensively cell-type vulnerability, and a deeper multimodal dataset in which CAG repeat expansion, huntingtin aggregation, six additional pathological readouts, and expression of 1,128 genes were measured in 185,721 cells, providing a comprehensive resource for the neurodegeneration community. C_LIO_LIDeep layer excitatory neuron loss (L5-6 NP and L6b) was associated with very large somatic CAG expansions (>380{+/-}55), while selective inhibitory neuron loss (chandelier and somatostatin interneurons) occurred with modest CAG repeat expansion or huntingtin intranuclear aggregation C_LIO_LIIntranuclear aggregation, not somatic repeat expansion, was more predictive of transcriptional changes, including chromatin remodeling and RNA export factors C_LI

neuroscience↗

bioRxiv2024

Acetylation of lysine 82 initiates TDP-43 nuclear loss of function by disrupting its nuclear import

The hallmark of a spectrum of age-dependent neurodegenerative diseases, including Amyotrophic Lateral Sclerosis (ALS), is a TDP-43 proteinopathy that includes nuclear loss of function and cytoplasmic aggregation. Here, reduced proteasome activity, as naturally occurs during aging, is shown to inhibit nuclear import of TDP-43. Quantitative mass spectrometry is used to determine that TDP-43 is the protein whose nuclear localization is most perturbed upon reduction in proteasome activity, culminating in elevated cytoplasmic TDP-43. Interaction of importin-1 with the bipartite classical nuclear localization sequence (cNLS) of TDP-43 is shown to be disrupted by partial proteasome inhibition but maintained by replacement with a PY-NLS that is recognized by importin-{beta}2. Mechanistically, this nuclear depletion of TDP-43 is shown to be driven by ubiquitination or acetylation of lysines 79, 82, and 84 within the cNLS when proteasome activity is reduced in human neurons. Specifically, acetylation at lysine 82 is sufficient to abolish TDP-43 binding to importin-1 and subsequent nuclear import of TDP-43. Moreover, using acetylation-specific TDP-43 antibodies, we detected acetylation of lysine 82 in the motor cortex of sporadic ALS patients but not control subjects. Our findings demonstrate that post-translational acetylation at lysine 82 of TDP-43 drives disruption of its importin-1-mediated nuclear import and is sufficient to initiate TDP-43 nuclear loss of function and cytoplasmic accumulation, evidence supporting acetylation as a plausible initiator of TDP-43 proteinopathies.

neuroscience↗

bioRxiv2024

Frontotemporal dementia-like disease progression elicited by seeded aggregation and spread of FUS

RNA binding proteins have emerged as central players in the mechanisms of many neurodegenerative diseases. In particular, a proteinopathy of fused in sarcoma (FUS) is present in some instances of familial Amyotrophic lateral sclerosis (ALS) and about 10% of sporadic FTLD. Here we establish that focal injection of sonicated human FUS fibrils into brains of mice in which ALS-linked mutant or wild-type human FUS replaces endogenous mouse FUS is sufficient to induce focal cytoplasmic mislocalization and aggregation of mutant and wild-type FUS which with time spreads to distal regions of the brain. Human FUS fibril-induced FUS aggregation in the mouse brain of humanized FUS mice is accelerated by an ALS-causing FUS mutant relative to wild-type human FUS. Injection of sonicated human FUS fibrils does not induce FUS aggregation and subsequent spreading after injection into naive mouse brains containing only mouse FUS, indicating a species barrier to human FUS aggregation and its prion-like spread. Fibril-induced human FUS aggregates recapitulate pathological features of FTLD including increased detergent insolubility of FUS and TAF15 and amyloid-like, cytoplasmic deposits of FUS that accumulate ubiquitin and p62, but not TDP-43. Finally, injection of sonicated FUS fibrils is shown to exacerbate age-dependent cognitive and behavioral deficits from mutant human FUS expression. Thus, focal seeded aggregation of FUS and further propagation through prion-like spread elicits FUS-proteinopathy and FTLD-like disease progression.

neuroscience↗

bioRxiv2024

Re-activation of neurogenic niches in aging brain

Recent studies proposing induced glia-to-neuron conversion raised the potential for generating new neurons to replace those lost due to injury, aging or neurodegenerative diseases. Here, single-cell spatial transcriptomics [Multiplexed Error Robust Fluorescence In Situ Hybridization (MERFISH)] is used to construct a spatial cell atlas of the subventricular and dentate gyrus neurogenic niches of young and aged adult murine brain. RNAs that encode the RNA binding protein Polypyrimidine Tract-Binding Protein (PTBP1) in the aged murine brain are determined to be highest in glia that line previously active neurogenic niches. A glial cell population with ependymal character within an initially quiescent subventricular neurogenic niche in the aged murine brain is identified that upon transient suppression of PTBP1 reenters the cell cycle, replicates DNA, and converts into neurons through a canonical adult neurogenesis pathway. Glia-derived neurons migrate from this niche, with some neurons transiting to the striatum and acquiring a transcriptome characteristic of GABAergic inhibitory neurons. Similar PTBP1 expressing quiescent glia are identified in the corresponding neurogenic niche of aged human brain. Thus, transient reduction of PTBP1 holds potential for inducing the generation of new neurons in quiescent neurogenic niches of the aged nervous system, thereby offering promising therapeutic applications. Bullet point summary1) Single-cell spatial transcriptomics is used to validate active neurogenesis in the two neurogenic niches of the young adult murine brain, determine that those niches are quiescent in the aging adult brain of mice, and demonstrate the absence of neurogenesis in the aging human brain. 2) The RNA binding protein PTBP1 is determined to be most highly expressed within glia that line the aged murine and human neurogenic niches, with its transient reduction sufficient in mice to activate/re-activate expression of genes characteristic of immature neurons. 3) Suppression of PTBP1 using a single intra-cerebral-ventricular injection of PTBP1-targeting antisense oligonucleotide (ASO) induces generation of new immature neurons in the neurogenic niches of the aged mouse brain via a canonical adult neurogenesis pathway. 4) Single-cell RNA signature tracing is used to identify a) a subclass of ependymal cells in a previously quiescent neurogenic niche of the aged mouse brain that convert into GABAergic inhibitory neurons following transient suppression of PTBP1, and b) the molecular steps in the conversion process including cell cycle re-entry, DNA replication, and transcriptome changes that mimic canonical neurogenesis. 5) A similar class of PTBP1-expressing ependymal cells lining the ventricle of the aging non-human primate and human brains is identified, suggesting the promise of re-activation of neurogenesis as a therapeutic approach in humans.

neuroscience↗

bioRxiv2023

Aberrant splicing in Huntington's disease via disrupted TDP-43 activity accompanied by altered m6A RNA modification.

Huntingtons disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the first exon of the HTT gene encoding huntingtin. Prior reports have established a correlation between CAG expanded HTT and altered gene expression. However, the mechanisms leading to disruption of RNA processing in HD remain unclear. Here, our analysis of the reported HTT protein interactome identifies interactions with known RNA-binding proteins (RBPs). Total, long-read sequencing and targeted RASL-seq of RNAs from cortex and striatum of the HD mouse model R6/2 reveals increased exon skipping which is confirmed in Q150 and Q175 knock-in mice and in HD human brain. We identify the RBP TDP-43 and the N6-methyladenosine (m6A) writer protein methyltransferase 3 (METTL3) to be upstream regulators of exon skipping in HD. Along with this novel mechanistic insight, we observe decreased nuclear localization of TDP-43 and cytoplasmic accumulation of phosphorylated TDP-43 in HD mice and human brain. In addition, TDP-43 co-localizes with HTT in human HD brain forming novel nuclear aggregate-like bodies distinct from mutant HTT inclusions or previously observed TDP-43 pathologies. Binding of TDP-43 onto RNAs encoding HD-associated differentially expressed and aberrantly spliced genes is decreased. Finally, m6A RNA modification is reduced on RNAs abnormally expressed in striatum from HD R6/2 mouse brain, including at clustered sites adjacent to TDP-43 binding sites. Our evidence supports TDP-43 loss of function coupled with altered m6A modification as a novel mechanism underlying alternative splicing/unannotated exon usage in HD and highlights the critical nature of TDP-43 function across multiple neurodegenerative diseases.

neuroscience↗

bioRxiv2021

Heat shock chaperone HSPB1 regulates cytoplasmic TDP-43 phase separation and liquid-to-gel transition

While the RNA binding protein TDP-43 reversibly phase separates within nuclei into complex droplets (anisosomes) with TDP-43-containing liquid outer shells and liquid centers of HSP70 family chaperones, cytoplasmic aggregates of TDP-43 are hallmarks of multiple neurodegenerative diseases, including ALS. Here we show that transient oxidative stress, proteasome inhibition, or inhibition of HSP70s ATP-dependent chaperone activity provokes reversible cytoplasmic TDP-43 de-mixing and transition from liquid to gel/solid, independent of RNA binding or stress granules. Isotope labeling mass spectrometry is used to identify that phase separated cytoplasmic TDP-43 is primarily bound by the small heat shock protein HSPB1. Binding is direct, mediated through TDP-43s RNA binding and low complexity domains. HSPB1 partitions into TDP-43 droplets, inhibits TDP-43 assembly into fibrils, and is essential for disassembly of stress-induced, TDP-43 droplets. Decrease of HSPB1 promotes cytoplasmic TDP-43 de-mixing and mislocalization. HSPB1 depletion is identified within ALS-patient spinal motor neurons containing aggregated TDP-43. These findings identify HSPB1 to be a regulator of cytoplasmic TDP-43 phase separation and aggregation.

cell biology↗

bioRxiv2021

Nuclear depletion of RNA binding protein ELAVL3 (HuC) in sporadic and familial amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a progressive fatal neurodegenerative disease caused by loss of motor neurons and characterized neuropathologically in almost all cases by nuclear depletion and cytoplasmic aggregation of TDP-43, a nuclear RNA binding protein (RBP). We identified ELAVL3 as one of the most downregulated genes in our transcriptome profiles of laser captured microdissection of motor neurons from sporadic ALS nervous systems and the top dysregulated RBPs. Neuropathological characterizations showed ELAVL3 nuclear depletion in a great percentage of remnant motor neurons, sometimes accompanied by cytoplasmic accumulations. These abnormalities were common in sporadic cases with and without intermediate expansions in ATXN2 and familial cases carrying mutations in C9orf72 and SOD1. Depletion of ELAVL3 occurred at both the RNA and protein levels and a short protein isoform was identified but it is not related to a TDP-43-dependent cryptic exon in intron 3. Strikingly, ELAVL3 abnormalities were more frequent than TDP-43 abnormalities and occurred in motor neurons still with normal nuclear TDP-43 present, but all neurons with abnormal TDP-43 also had abnormal ELAVL3. In a neuron-like cell culture model using SH-SY5Y cells, ELAVL3 mislocalization occurred weeks before TDP-43 abnormalities were seen. We interrogated genetic databases but did not identify association of ELAVL3 genetic structure associated with ALS. Taken together, these findings suggest that ELAVL3 is an important RBP in ALS pathogenesis acquired early and the neuropathological data suggest it is involved by loss of function rather than cytoplasmic toxicity.

neuroscience↗

bioRxiv2020

TDP-43 and HSP70 phase separate into anisotropic, intranuclear liquid spherical annuli

The RNA binding protein TDP-43 naturally phase separates within cell nuclei and forms cytoplasmic aggregates in age-related neurodegenerative diseases. Here we show that acetylation-mediated inhibition of TDP-43 binding to RNA produces co-de-mixing of acetylated and unmodified TDP-43 into symmetrical, intranuclear spherical annuli whose shells and cores have liquid properties. Shells are anisotropic, like liquid crystals. Consistent with our modelling predictions that annulus formation is driven by components with strong self-interactions but weak interaction with TDP-43, the major components of annuli cores are identified to be HSP70 family proteins, whose chaperone activity is required to maintain liquidity of the core. Proteasome inhibition, mimicking reduction in proteasome activity during aging, induces TDP-43-containing annuli in neurons in rodents. Thus, we identify that TDP-43 phase separation is regulated by acetylation, proteolysis, and ATPase-dependent chaperone activity of HSP70. One Sentence SummaryAcetylation of TDP-43 drives its phase separation into spherical annuli that form a liquid-inside-a-liquid-inside-a-liquid.

cell biology↗

bioRxiv2019

The endosomal protein sorting nexin 4 is a novel synaptic protein

Sorting nexin 4 (SNX4) is an evolutionary conserved protein that mediates recycling from the endosomes back to the plasma membrane in yeast and mammalian cells. SNX4 is expressed in the brain, but its neuronal localization and function have not been addressed. Using a new antibody, endogenous neuronal SNX4 co-localized with both early and recycling endosomes, similar to the reported localization of SNX4 in non-neuronal cells. Neuronal SNX4 was accumulated in synapses, and immuno-electron microscopy revealed that SNX4 was predominantly localized to presynaptic terminals. Acute depletion of neuronal SNX4 using independent shRNAs did not affect the levels of the canonical SNX4-cargo transferrin receptor. Explorative mass spectrometry showed that each SNX4-targetted shRNA resulted in a reproducible and distinct proteome and that synaptic communication-related proteins were downregulated upon expression of the three shRNAs. The identification of SNX4 as a novel synaptic protein indicates a selective demand for SNX4 dependent sorting in synapses.

neuroscience↗