Biology subjects

Jorgens, D. M.

Publications and source records attributed to Jorgens, D. M..

10 recordsLinked to original sources

bioRxiv2026

miR-34/449 miRNAs regulate choroid plexus ciliogenesis to control cerebrospinal fluid production

A developmental increase in cerebrospinal fluid (CSF) production during development is essential for neuronal growth and ventricular expansion. A key regulator of CSF production is the specialized sensory multicilia of the choroid plexus (ChP), which mediate non-canonical Sonic hedgehog (Shh) signaling to suppress water channel and ion transporter expression, thereby limiting CSF production. ChP multicilia progressively shortens during development, attenuating Shh signaling and promoting CSF production. Here, we identify miR-34/449 miRNAs as essential regulators of ChP multiciliogenesis. Whereas mutations in canonical ciliogenesis genes elevate CSF production and contribute to hydrocephaly, deletion of miR-34/449 reduces CSF volume and causes microcephaly. Loss of miR-34/449 miRNAs causes excessive basal body amplification, defective basal body docking, and failure of developmental multiciliary shortening. Consequently, miR-34/449-deficient ChP cilia remain abnormally long and fail to attenuate Shh signaling, resulting in sustained repression of water channel and ion transporter expression and reduced CSF production. Mechanistically, miR-34/449 miRNAs directly target Gmnc, a master transcriptional regulator of multiciliogenesis, to restrain basal body amplification and promote basal body docking. Together, our findings identify miR-34/449 miRNAs as critical regulators of ChP multiciliogenesis and establish the developmental remodeling of ChP multicilia as a mechanism to couple Shh signaling dynamics to developmental control of CSF production.

developmental biology↗

bioRxiv2026

Actin disassembly triggers CNS myelin compaction and wrapping

Compact myelin enables rapid and precise impulse conduction in the vertebrate nervous system. During CNS development, oligodendrocytes wrap spirally around axons while compacting membranes, yet how cytoskeletal remodeling is coupled to these events remains unclear. Actin disassembly is required for wrapping, but whether wrapping is driven by iterative actin-based protrusion or follows a transition to actin-independent mechanisms is unresolved. Here we integrate tract-resolved developmental profiling, live-cell compaction mapping, and in vivo genetic perturbation to define how actin disassembly is coupled to myelin wrapping. We find that actin filaments undergo pronounced, sustained disassembly before active wrapping begins, with little evidence for persistent actin within sheaths during wrapping. We develop a live-cell assay that maps membrane compaction in cultured oligodendrocytes and show that compaction zones are depleted of actin filaments and expand when actin disassembly is promoted. Consistent with this model, oligodendrocyte-specific actin disassembly in vivo accelerates the appearance of thicker myelin early in development. Together, our results support a model in which actin disassembly promotes myelin wrapping by enabling membrane compaction, and provide a platform to dissect how compaction is regulated in development and disease.

neuroscience↗

bioRxiv2026

Ca2+ influx through ER-plasma membrane contacts is required for brown fat thermogenesis and metabolic health

Brown adipose tissue (BAT) exhibits exceptional metabolic plasticity, rapidly increasing energy expenditure to sustain thermogenesis during cold exposure. This high metabolic activity imposes substantial demands on cellular systems, requiring robust adaptive mechanisms to maintain homeostasis and prevent cellular stress. Yet, the pathways that support and coordinate these adaptive responses in brown adipocytes remain incompletely understood. Here, we identify a cold-induced adaptive program in BAT characterized by the formation of endoplasmic reticulum-plasma membrane (ER-PM) contact sites and the activation of store-operated calcium entry (SOCE), which is essential for maintaining brown adipocyte health during thermogenic activation. Cold exposure enhances ER-PM contacts and upregulates the expression of STIM and Orai proteins, key mediators of SOCE. Loss of STIM in brown adipocytes disrupts intracellular Ca{superscript 2} homeostasis and induces aberrant aggregation of ER membranes. STIM deficiency also impairs cold-induced mitochondrial fission resulting in hyperfused mitochondria with reduced oxidative capacity, independently of UCP1 abundance. Importantly, mice lacking STIM in BAT exhibit impaired lipid oxidation, are cold intolerant and develop exacerbated peripheral insulin resistance when challenged with a high-fat diet. Together, these findings identify ER-PM remodeling and STIM-mediated SOCE as a central regulator that links organelle architecture to brown adipocyte function and contributes to whole-body metabolic homeostasis.

cell biology↗

bioRxiv2026

Volume EM reveals three-dimensional architecture of the desmosome in epithelial cells and tissue models

Desmosomes are a type of cell-cell adhesive junction present in cardiac tissue and epithelial tissues such as the epidermis. These intercellular junctions anchor to the intermediate filament cytoskeleton, providing mechanical integrity to the tissues in which they reside. Our understanding of desmosome architecture has largely been influenced by observations of two-dimensional images obtained through conventional electron microscopy. Here, using focused ion beam scanning electron microscopy, we report the three-dimensional ultrastructure of desmosomes in A431 and S1 human mammary epithelial cells. We also reveal differences in desmosome ultrastructure at homo- and heterotypic junctions of human nasal airway epithelial cells. Quantitative analyses of these volume EM datasets reveal variations in desmosome size, shape, and organization. Importantly, we report the presence of discontinuities or "holes" within the desmosome outer dense plaque, a novel feature that is observed in either one or both halves of a desmosome. This study provides the first comprehensive description of the epithelial desmosome as a three-dimensional structure, and emphasizes the need to investigate the effects of dynamic morphogenetic processes and disease states on desmosome ultrastructure.

cell biology↗

bioRxiv2025

Tom70-mediated mitochondria-nuclear envelope contacts regulate nuclear pore complex inheritance during gametogenesis

Gametogenesis rejuvenates the cellular lineage and excludes senescence-associated factors from gametes. In Saccharomyces cerevisiae, this involves sequestration of nuclear constituents into the Gametogenesis-Uninherited Nuclear Compartment (GUNC), which is excluded from gametes. Here we identify the conserved mitochondrial import receptor Tom70 as a key regulator of GUNC-mediated exclusion. Loss of TOM70 disrupts the sequestration of nuclear pore complexes, but not senescence-associated aggregates and nucleolar components, into the GUNC. Tom70s role appears independent of its canonical function in mitochondrial import and instead reflects a meiosis-specific requirement for mitochondria-nuclear envelope tethering. During meiosis II, Tom70 concentrates around the GUNC, where it recruits the nuclear envelope tethering protein Cnm1. Loss of CNM1 partially phenocopies tom70{Delta}, consistent with parallel tethering interactions. These findings uncover a previously unrecognized organelle contact-dependent pathway that remodels the nuclear envelope to support selective nuclear inheritance. More broadly, they highlight how organelle contacts integrate with nuclear quality control to safeguard gamete integrity.

cell biology↗

bioRxiv2024

Enhanced RNA replication and pathogenesis in recent SARS-CoV-2 variants harboring the L260F mutation in NSP6

The COVID-19 pandemic has been driven by SARS-CoV-2 variants with enhanced transmission and immune escape. Apart from extensive evolution in the Spike protein, non-Spike mutations are accumulating across the entire viral genome and their functional impact is not well understood. To address the contribution of these mutations, we reconstructed genomes of recent Omicron variants with disabled Spike expression (replicons) to systematically compare their RNA replication capabilities independently from Spike. We also used a single reference replicon and complemented it with various Omicron variant Spike proteins to quantify viral entry capabilities in single-round infection assays. Viral entry and RNA replication were negatively correlated, suggesting that as variants evolve reduced entry functions under growing immune pressure on Spike, RNA replication increases as a compensatory mechanism. We identified multiple mutations across the viral genome that enhanced viral RNA replication. NSP6 emerged as a hotspot with a distinct L260F mutation independently arising in the BQ.1.1 and XBB.1.16 variants. Using mutant and revertant NSP6 viral clones, the L260F mutation was validated to enhance viral replication in cells and increase pathogenesis in mice. Notably, this mutation enhanced host lipid droplet consumption by NSP6 without impacting its known ER-zippering function or double-membrane vesicle morphology. Collectively, a systematic analysis of RNA replication of recent Omicron variants defined NSP6s key role in viral RNA replication that provides insight into evolutionary trajectories of recent variants with possible therapeutic implications. Author SummaryAs SARS-CoV-2 continues to spread and adapt in humans, viral variants with enhanced spread and immune evasion have emerged throughout the COVID-19 pandemic. While most of the mutations occur in the Spike protein and have been extensively studied, non-Spike mutations have been accumulating and are not as well understood. Here, we constructed Spike-defective genomes of recent Omicron variants and systematically compared their RNA replication capabilities independently from Spike. We also performed single-round infection assays with various Omicron variant Spike proteins to quantify viral entry capabilities. Interestingly, viral entry and RNA replication were negatively correlated, suggesting that as variants evolved reduced entry functions under growing immune pressure on Spike, RNA replication increased as a compensatory mechanism. We focused on a viral protein NSP6 that acquired mutations that significantly enhanced RNA replication. We validated that a frequently accessed L260F mutation in NSP6 enhanced viral infection in cells and increased pathogenesis in mice. While the mutation did not alter NSP6s role in maintaining a membranous network of viral replication factories, the mutation enhanced viral hijacking of the host lipid droplet machinery. Collectively, we highlight the important role of non-Spike mutations in the evolutionary trajectories of SARS-CoV-2 variants with possible monitoring and therapeutic implications.

microbiology↗

bioRxiv2024

TOMM40 regulates hepatocellular and plasma lipid metabolism via an LXR-dependent pathway

The gene encoding TOMM40 (Transporter of Outer Mitochondrial Membrane 40) is adjacent to that encoding APOE, which has a central role in lipid and lipoprotein metabolism. Human genetic variants near APOE and TOMM40 are strongly associated with plasma lipid levels, but a specific role for TOMM40 in lipid metabolism has not been established. Investigating this, we show that suppression of TOMM40 in human hepatoma cells upregulates expression of APOE and LDLR in part via activation of LXRB (NR1H2) by oxysterols, with consequent increased uptake of VLDL and LDL. This is in part due to disruption of mitochondria-endoplasmic reticulum contact sites, with resulting accrual of reactive oxygen species and non-enzymatically derived oxysterols. With TOMM40 knockdown, cellular triglyceride and lipid droplet content are increased, effects attributable in part to receptor-mediated VLDL uptake, since lipid staining is significantly reduced by concomitant suppression of either LDLR or APOE. In contrast, cellular cholesterol content is reduced due to LXRB-mediated upregulation of the ABCA1 transporter as well as increased production and secretion of oxysterol-derived cholic acid. Consistent with the findings in hepatoma cells, in vivo knockdown of TOMM40 in mice results in significant reductions of plasma triglyceride and cholesterol concentrations, reduced hepatic cholesterol and increased triglyceride content, and accumulation of lipid droplets leading to development of steatosis. These findings demonstrate a role for TOMM40 in regulating hepatic lipid and plasma lipoprotein levels and identify mechanisms linking mitochondrial function with lipid metabolism. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=132 SRC="FIGDIR/small/600910v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@17b0c8forg.highwire.dtl.DTLVardef@17599aaorg.highwire.dtl.DTLVardef@1bb6ab2org.highwire.dtl.DTLVardef@15a035f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

CLCC1 promotes hepatic neutral lipid flux and nuclear pore complex assembly

Imbalances in lipid storage and secretion lead to the accumulation of hepatocyte lipid droplets (LDs) (i.e., hepatic steatosis). Our understanding of the mechanisms that govern the channeling of hepatocyte neutral lipids towards cytosolic LDs or secreted lipoproteins remains incomplete. Here, we performed a series of CRISPR-Cas9 screens under different metabolic states to uncover mechanisms of hepatic neutral lipid flux. Clustering of chemical-genetic interactions identified CLIC-like chloride channel 1 (CLCC1) as a critical regulator of neutral lipid storage and secretion. Loss of CLCC1 resulted in the buildup of large LDs in hepatoma cells and knockout in mice caused liver steatosis. Remarkably, the LDs are in the lumen of the ER and exhibit properties of lipoproteins, indicating a profound shift in neutral lipid flux. Finally, remote homology searches identified a domain in CLCC1 that is homologous to yeast Brl1p and Brr6p, factors that promote the fusion of the inner and outer nuclear envelopes during nuclear pore complex assembly. Loss of CLCC1 lead to extensive nuclear membrane herniations, consistent with impaired nuclear pore complex assembly. Thus, we identify CLCC1 as the human Brl1p/Brr6p homolog and propose that CLCC1-mediated membrane remodeling promotes hepatic neutral lipid flux and nuclear pore complex assembly.

cell biology↗

bioRxiv2023

Self-organizing actin networks drive sequential endocytic protein recruitment and vesicle release on synthetic lipid bilayers

Forces generated by actin assembly assist membrane invagination during clathrin-mediated endocytosis (CME). The sequential recruitment of core endocytic proteins and regulatory proteins, and assembly of the actin network, are well documented in live cells and are highly conserved from yeasts to humans. However, understanding of CME protein self-organization, as well as the biochemical and mechanical principles that underlie actins role in CME, is lacking. Here, we show that supported lipid bilayers coated with purified yeast WASP, an endocytic actin assembly regulator, and incubated in cytoplasmic yeast extracts, recruit downstream endocytic proteins and assemble actin tails. Time-lapse imaging of WASP-coated bilayers revealed sequential recruitment of proteins from different endocytic modules, faithfully replicating in vivo behavior. Reconstituted actin networks assemble in a WASP-dependent manner and deform lipid bilayers, as seen by electron microscopy. Time-lapse imaging revealed that vesicles are released from the lipid bilayers with a burst of actin assembly. Actin networks pushing on membranes have previously been reconstituted; here, we have reconstituted a biologically important variation of these actin networks that self-organize on bilayers and produce pulling forces sufficient to bud off membrane vesicles. We propose that actin-driven vesicle generation may represent an ancient evolutionary precursor to diverse vesicle forming processes adapted for a wide array of cellular environments and applications. Significance StatementActin filament assembly participates in many vesicle-forming processes. However, the underlying principles for how assembly is initiated and organized to effectively harness assembly forces remain elusive. To address this gap, we report a novel reconstitution of actin-driven vesicle release from supported lipid bilayers. Using real-time imaging, we observe sequential recruitment of endocytic proteins and, following a burst of actin assembly, vesicle release from bilayers. Given the absence of cargo or upstream endocytic regulatory proteins on the bilayers, and the participation of actin in many vesicle-forming processes, we posit that this mode of vesicle formation represents an early evolutionary precursor for multiple trafficking pathways. We expect that this assay will be of great use for future investigations of actin-mediated vesicle-forming processes.

cell biology↗

bioRxiv2019

Meiotic cellular rejuvenation is coupled to nuclear remodeling in budding yeast

Production of healthy gametes in meiosis relies on the quality control and proper distribution of both nuclear and cytoplasmic contents. Meiotic differentiation naturally eliminates age-induced cellular damage by an unknown mechanism. Using time-lapse fluorescence microscopy in budding yeast, we found that nuclear senescence factors - including protein aggregates, extrachromosomal ribosomal DNA circles, and abnormal nucleolar material - are sequestered away from chromosomes during meiosis II and subsequently eliminated. A similar sequestration and elimination process occurs for the core subunits of the nuclear pore complex in both young and old cells. Nuclear envelope remodeling drives the formation of a membranous compartment containing the sequestered material. Importantly, de novo generation of plasma membrane is required for the sequestration event, preventing the inheritance of long-lived nucleoporins and senescence factors into the newly formed gametes. Our study uncovers a new mechanism of nuclear quality control and provides insight into its function in meiotic cellular rejuvenation.

cell biology↗