Biology subjects

Hoogenraad, C.

Publications and source records attributed to Hoogenraad, C..

10 recordsLinked to original sources

bioRxiv2026

A scalable human neuron model of Alzheimer's disease relevant tauopathy reveals mechanisms linking Tau fibrillization to synaptic dysfunction

Tauopathies, including Alzheimer's disease, are driven by pathological aggregation of hyperphosphorylated Tau, which disrupts synaptic integrity, impairs neuronal communication, and contributes to cognitive decline. To dissect tauopathy pathogenesis and enable therapeutic discovery, reliable and scalable human iPSC-neuron models are essential. Here, we developed two complementary iPSC-derived neuron models: an endogenous Tau seeding model, in which neurons are challenged with pre-formed Tau fragments that form paired helical filament (PHF)-consistent structures, and a Tau-0N3R overexpression seeding model to accelerate pathology. Both models recapitulate hallmark features of tauopathy, including the progressive formation of intracellular, hyperphosphorylated, sarkosyl-insoluble, and conformationally altered Tau aggregates (AT8, MC1 positive), along with synaptic and neuronal dysfunction. Cryogenic electron tomography (cryo-ET) further revealed the morphology of Tau fibrils within cells, as well as the ultrastructure of Tau fibrils trapping synaptic vesicles in situ. Using this platform, we performed integrated phosphoproteomics, high-content screening, and functional validation to identify key pathways driving Tau aggregation. MARK2-mediated phosphorylation within Tau's microtubule-binding domain emerged as an early trigger of aggregation, confirmed by site-specific mutagenesis. In parallel, small molecules targeting the PI3K/mTOR/GSK3 pathway reduced aggregation and restored synaptic function, with GSK3 inhibition lowering phosphorylation at critical aggregation-driving sites on Tau. Together, these findings establish a physiologically relevant, scalable platform for therapeutic screening that connects Tau seed uptake, site-specific phosphorylation, fibril formation, and synaptic disruption, ultimately identifying mechanistically separable intervention points along the aggregation cascade.

cell biology↗

bioRxiv2026

Hypothalamic oligodendrocytes regulate systemic energy balance through Notch-dependent state transitions

The central mechanisms through which glial cells regulate whole-body metabolism remain poorly understood. Here, we identify Notch signaling in hypothalamic oligodendrocyte lineage cells as a previously unrecognized regulator of systemic energy homeostasis. Pharmacological inhibition of the Notch ligands Jagged1 (Jag1) and Jagged2 (Jag2) induces rapid and reversible weight loss across diverse physiological and metabolic contexts independently of toxicity or caloric intake. Single-nucleus transcriptomic analyses identify hypothalamic oligodendrocyte precursor cells (OPCs) as the principal Notch-responsive population following systemic Jag1/2 inhibition and reveal expansion of a metabolically specialized GPR17 intermediate state characterized by enhanced oxidative metabolism and increased predicted communication with hypothalamic neurons. This glial remodeling is accompanied by fasting-like transcriptional reprogramming of AgRP neurons, reorganization of melanocortin-autonomic circuit activity, and activation of peripheral catabolic programs. Importantly, selective deletion of Notch1/2 in hypothalamic OPCs recapitulates the major physiological and metabolic effects of systemic Jag1/2 inhibition, establishing oligodendrocyte Notch signaling as a causal regulator of whole-body metabolism. Together, our findings establish Notch-dependent oligodendrocyte state transitions as a previously unrecognized mechanism linking glial plasticity to systemic energy homeostasis.

physiology↗

bioRxiv2022

Sodium channel endocytosis drives axon initial segment plasticity

Activity-dependent plasticity of the axon initial segment (AIS) endows neurons with the ability to adapt action potential output to changes in network activity. Action potential initiation at the AIS highly depends on the clustering of voltage-gated sodium channels, however the molecular mechanisms regulating their plasticity remain largely unknown. Here, we used novel genetic tools to endogenously label sodium channels and their scaffolding protein, to reveal their nanoscale organization and longitudinally image AIS plasticity in hippocampal neurons, in slices and primary cultures. We find that induction of NMDA receptor-mediated long-term synaptic depression is linked to a rapid and local endocytosis of sodium channels from the distal AIS. These data reveal a novel fundamental mechanism for rapid activity-dependent AIS reorganization sharing conserved features with synaptic plasticity.

neuroscience↗

bioRxiv2021

PTRN-1/CAMSAP and NOCA-2/NINEIN are required for microtubule polarity in Caenorhabditis elegans dendrites

The neuronal microtubule cytoskeleton is key to establish axon-dendrite polarity. Dendrites are characterized by the presence of minus-end out microtubules, however the mechanisms that organize these microtubules minus-end out is still poorly understood. Here, we characterized the role of two microtubule minus-end related proteins in this process in Caenorhabditis elegans, the microtubule minus-end stabilizing protein CAMSAP (PTRN-1) and a NINEIN homologue (NOCA-2). We found that CAMSAP and NINEIN function in parallel to mediate microtubule organization in dendrites. During dendrite outgrowth, RAB-11 positive vesicles localized to the dendrite tip function as a microtubule organizing center (MTOC) to nucleate microtubules. In the absence of either CAMSAP or NINEIN, we observed a low penetrance MTOC vesicles mis-localization to the cell body, and a nearly fully penetrant phenotype in double mutant animals. This suggests that both proteins are important for localizing the MTOC vesicles to the growing dendrite tip to organize microtubules minus-end out. Whereas NINEIN localizes to the MTOC vesicles where it is important for the recruitment of the microtubule nucleator {gamma}-tubulin, CAMSAP localizes around the MTOC vesicles and is co-translocated forward with the MTOC vesicles upon dendritic growth. Together, these results indicate that microtubule nucleation from the MTOC vesicles and microtubule stabilization are both important to localize the MTOC vesicles distally to organize dendritic microtubules minus-end out.

cell biology↗

bioRxiv2021

Organization and dynamics of the cortical complexes controlling insulin secretion in β-cells.

Insulin secretion in pancreatic {beta}-cells is regulated by cortical complexes that are enriched at the sites of adhesion to extracellular matrix facing the vasculature. Many components of these complexes, including Bassoon, RIM, ELKS and liprins, are shared with neuronal synapses. Here, we show that insulin secretion sites also contain non-neuronal proteins LL5{beta} and KANK1, which in migrating cells organize exocytotic machinery in the vicinity of integrin-based adhesions. Depletion of LL5{beta} or focal adhesion disassembly triggered by myosin II inhibition perturbed the clustering of secretory complexes and attenuated the first wave of insulin release. While previous analyses in vitro and in neurons suggested that secretory machinery might assemble through liquid-liquid phase separation, analysis of endogenously labeled ELKS in pancreatic islets indicated that its dynamics is inconsistent with such a scenario. Instead, fluorescence recovery after photobleaching and single molecule imaging showed that ELKS turnover is driven by binding and unbinding to low-mobility scaffolds. Both the scaffold movements and ELKS exchange were stimulated by glucose treatment. Our findings help to explain how integrin-based adhesions control spatial organization of glucose-stimulated insulin release.

cell biology↗

bioRxiv2019

Loss of BICD2 in muscle drives motor neuron loss in a developmental form of spinal muscular atrophy

BICD2 is a key component of the dynein/dynactin motor complex. Autosomal dominant mutations in BICD2 cause Spinal Muscular Atrophy Lower Extremity Predominant 2 (SMALED2), a developmental disease of motor neurons. In this study we sought to examine the motor neuron phenotype of conditional Bicd2-/- mice. Bicd2-/- mice show a significant reduction in the number of motor axons of the L4 ventral root compared to wild type mice. Muscle-specific knockout of Bicd2, but not motor neuron-specific Bicd2 loss, results in a reduction in L4 ventral axons comparable to global Bicd2-/- mice. Rab6, a small GTPase required for the sorting of secretory vesicles from the TGN to the plasma membrane is a major binding partner of BICD2. We therefore examined the secretory pathway in SMALED2 patient fibroblasts and demonstrated impaired flow of constitutive secretory cargoes. Together, these data indicate that BICD2 loss from muscles is a major driver of non-cell autonomous pathology with important implications for future therapeutic approaches to SMALED2. SummaryMissense mutations in the cargo adaptor protein BICD2 cause SMALED2, a developmental disease of motor neurons. In this study, the authors show that BICD2 mutations cause motor neuron loss by a non-cell autonomous mechanism determining a disabling impairment of muscle function.

neuroscience↗

bioRxiv2019

Tropomyosin Tpm3.1 is required to maintain the structure and function of the axon initial segment

The axon initial segment (AIS) is the site of action potential initiation and serves as a vesicular filter and diffusion barrier that help maintain neuronal polarity. Recent studies have revealed details about a specialized structural complex in the AIS. While an intact actin cytoskeleton is required for AIS formation, pharmacological disruption of actin polymerization compromises the AIS vesicle filter but does not affect overall AIS structure. In this study, we found that the tropomyosin isoform Tpm3.1 decorates a population of relatively stable actin filaments in the AIS. Inhibiting Tpm3.1 in cultured hippocampal neurons led to the loss of AIS structure, the AIS vesicle filter, the clustering of sodium ion channels, and reduced firing frequency. We propose that Tpm3.1-decorated actin filaments form a stable actin filament network under the AIS membrane which provides a scaffold for membrane organization and AIS proteins.

neuroscience↗

bioRxiv2019

Temporal quantitative proteomics of protein translation and phosphorylation in synaptic plasticity

At neuronal synapses, activation of metabotropic glutamate receptors (mGluR1/5) triggers a form of long-term depression (mGluR-LTD) that relies on new protein synthesis and the internalization of AMPA-type glutamate receptors. Dysregulation of these processes has been implicated in the development of mental disorders such as autism spectrum disorders and therefore merit a better understanding on a molecular level. Here, to study mGluR-LTD, we integrated quantitative high-resolution phosphoproteomics with the analyses of newly synthesized proteins via bio-orthogonal amino acids (azidohomoalanine) in a pulsed labeling strategy combined with tandem mass tag label-based quantification in cultured hippocampal neurons stimulated with DHPG. We identified several kinases with important roles in DHPG-mGluR-LTD, which we confirmed using small molecule kinase inhibitors. Furthermore, changes in the AMPA receptor endocytosis pathway in both protein synthesis and protein phosphorylation upon LTD were identified, whereby Intersectin-1 was validated as a vital player in this pathway. This study revealed several novel insights into the molecular mechanisms underlying mGluR-LTD and provides a broad view on its molecular basis, which serves as a rich resource for further analyses.

neuroscience↗

bioRxiv2019

Deciphering the protein dynamics and molecular determinants of iPSC-derived neurons.

Neuronal development is a multistep process with different regulatory programs that shapes neurons to form dendrites, axons and synapses. To date, knowledge on neuronal development is largely based on murine data and largely restricted to the genomic and transcriptomic level. Advances in stem cell differentiation now enable the study of human neuronal development, and here we provide a mass spectrometry-based quantitative proteomic signature, at high temporal resolution, of human stem cell-derived neurons. To reveal proteomic changes during neuronal development we make use of two differentiation approaches, either by expression of neurogenin-2 (Ngn2) leading to glutamatergic induced neurons (iN) or via small molecule manipulations, leading to patterned motor neurons. Our analysis revealed key proteins that show significant expression changes (FDR <0.001) during neuronal differentiation. We overlay our proteomics data with available transcriptomic data during neuronal differentiation and show distinct, datatype-specific, signatures. Overall, we provide a rich resource of information on proteins associated with human neuronal development, and moreover, highlight several signaling pathways involved, such as Wnt and Notch.

neuroscience↗

bioRxiv2019

Fibril formation rewires interactome of the Alzheimer protein Tau by π-stacking

Aggregation of the Tau protein defines progression of neurodegenerative diseases, including Alzheimers Disease. Tau assembles into oligomers and fibrils. The molecular basis of their toxicity is poorly understood. Here we show that {pi}-stacking by Arginine side chains rewires the interactome of Tau upon aggregation. Oligomeric nano-aggregates scavenge the COPI complex, fibrils attract proteins involved in microtubule binding, RNA binding and phosphorylation. The aberrant interactors have disordered regions with unusual sequence features. Arginines are crucial to initiate such aberrant interactions. Remarkably, substitution of Arginines by Lysines abolishes scavenging, which indicates a key role for the pi-stacking of the Arginine side chain. The molecular chaperone Hsp90 tames such re-arrangements, which suggests that the natural protein quality control system can suppress aberrant interactions. Together, our data present a molecular mode of action for derailment of protein-protein interaction in neurodegeneration.\n\nHIGHLIGHTSO_LITau fibrils act as fishing net for proteins.\nC_LIO_LITau fibrils attract specific protein families associated with Alzheimer.\nC_LIO_LI{pi}-stacking by Arginines key for aberrant binding to Tau fibrils\nC_LIO_LIThe Hsp90 chaperone stalls fibril growth and alters interactome\nC_LI

biochemistry↗