Biology subjects

Bowser, R.

Publications and source records attributed to Bowser, R..

7 recordsLinked to original sources

bioRxiv2021

Tau aggregates are RNA-protein assemblies that mis-localize multiple nuclear speckle components

Tau aggregates contribute to neurodegenerative diseases including frontotemporal dementia and Alzheimers disease (AD). Although RNA promotes tau aggregation in vitro, whether tau aggregates in cells contain RNA is unknown. We demonstrate in cell culture and mouse brains that both cytosolic and nuclear tau aggregates contain RNA, with enrichment for snRNAs and snoRNAs. Nuclear tau aggregates colocalize with and alter the composition, dynamics, and organization of nuclear speckles, which are membraneless organelles involved in pre-mRNA splicing. Moreover, several nuclear speckle components, including SRRM2, mislocalize to cytosolic tau aggregates in cells, mouse brains, and patient brains with AD, frontotemporal dementia (FTD), and corticobasal degeneration (CBD). Consistent with these alterations we observe the presence of tau aggregates is sufficient to alter pre-mRNA splicing. This work identifies tau alteration of nuclear speckles as a feature of tau aggregation that may contribute to the pathology of tau aggregates.

molecular biology↗

bioRxiv2021

Defining the Caprin-1 interactome in unstressed and stressed conditions

Cytoplasmic stress granules (SGs) are dynamic non-membranous foci containing translationally arrested mRNA and RNA binding proteins that form in response to a variety of cellular stressors. SGs may evolve into the cytoplasmic inclusions observed in many neurodegenerative diseases. Recent studies have examined the SG proteome by interrogating the interactome of G3BP1, a core SG protein. To gain further insight into the SG proteome, we employed an immunoprecipitation coupled with mass spectrometry approach of endogenous Caprin-1 in HeLa cells under unstressed or stressed conditions. Overall, we identified ~1,500 proteins that interact with Caprin-1. Interactors under stressed conditions were primarily annotated to the ribosome, spliceosome, and RNA transport pathways. We validated four Caprin-1 interactors that localized to arsenite-induced SGs: ANKHD1, Talin-1, GEMIN5, and SNRNP200. We also validated these stress-induced interactions in SH-SY5Y cells and determined that SNRNP200 also associated with osmotic and thermal induced SGs. Finally, we identified SNRNP200 in cytoplasmic aggregates in ALS spinal cord and motor cortex. Collectively, our findings provide the first description of the Caprin-1 protein interactome, identify novel cytoplasmic SG components, and reveal a SG protein in cytoplasmic aggregates in ALS patients. Proteomic data collected in this study are available via ProteomeXchange with identifier PXD023271.

cell biology↗

bioRxiv2020

Activated iPSC-microglia from C9orf72 ALS/FTD patients exhibit endosomal-lysosomal dysfunction

While motor and cortical neurons are affected in C9orf72 ALS/FTD, it remains still largely unknown if and how non-neuronal cells induce or exacerbate neuronal damage. We generated C9orf72 ALS/FTD patient-derived induced pluripotent stem cells differentiated into microglia (iPSC-MG) and examined their intrinsic phenotypes. Similar to iPSC motor neurons, C9orf72 ALS/FTD iPSC-MG mono-cultures form G4C2 repeat RNA foci, exhibit reduced C9orf72 protein levels and generate dipeptide repeat proteins. Healthy control and C9orf72 iPSC-MG equivalently express microglial specific genes and display microglial functions including inflammatory cytokine release and phagocytosis of extracellular toxic cargos such as synthetic amyloid beta peptides and healthy human brain synaptoneurosomes. Select C9orf72 iPSC-MG patient lines show inability to efficiently remove phagocytosed contents, suggesting dysfunction of the endosomal-lysosomal pathways. Finally, RNA sequencing revealed overall transcriptional changes in diseased microglia yet no significant differentially expressed microglial-enriched genes. These minimal differences in cellular, molecular and functional characteristics of microglial mono-cultures suggest that a diseased microenvironment is associated with microglial activation and subsequent regulation of neuronal dysfunction.

neuroscience↗

bioRxiv2020

TDP-43 proteinopathy alters the ribosome association of multiple mRNAs including the glypican Dally-like protein (Dlp)/GPC6

Amyotrophic lateral sclerosis (ALS) is a genetically heterogeneous neurodegenerative disease in which 97% of patients exhibit cytoplasmic aggregates containing the RNA binding protein TDP-43. Using tagged ribosome affinity purifications in Drosophila models of TDP-43 proteinopathy, we identified TDP-43 dependent translational alterations in motor neurons impacting the spliceosome, pentose phosphate and oxidative phosphorylation pathways. A subset of the mRNAs with altered ribosome association are also enriched in TDP-43 complexes suggesting that they may be direct targets. Among these, dlp mRNA, which encodes the glypican Dally like protein (Dlp)/GPC6, a wingless (Wg/Wnt) signaling regulator is insolubilized both in flies and patient tissues with TDP-43 pathology. While Dlp/GPC6 forms puncta in the Drosophila neuropil and ALS spinal cords, it is reduced at the neuromuscular synapse in flies suggesting compartment specific effects of TDP-43 proteinopathy. These findings together with genetic interaction data show that Dlp/GPC6 is a novel, physiologically relevant target of TDP-43 proteinopathy.

neuroscience↗

bioRxiv2019

RBM45 associates with nuclear stress bodies and forms nuclear inclusions during chronic cellular stress and in neurodegenerative diseases

RBM45 is a multifunctional RNA binding protein (RBP) found in cytoplasmic and nuclear inclusions in amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD), and Alzheimers disease (AD). While cytoplasmic RBM45 inclusions contain other disease-associated proteins, nuclear RBM45 inclusions are morphologically and biochemically distinct from previously described nuclear inclusion pathology in these diseases. To better understand nuclear RBM45 aggregation and inclusion formation, we evaluated the association of RBM45 with a variety of membraneless nuclear organelles, including nuclear speckles, Cajal bodies, and nuclear gems. Under basal conditions, RBM45 is diffusely distributed throughout the nucleus and does not localize to a specific nuclear organelle. During cellular stress, however, the nuclear RBM45 distribution undergoes an RNA-binding dependent rearrangement wherein RBM45 coalesces into a small number of nuclear puncta. These puncta contain the nuclear stress body (NSB) markers heat shock factor 1 (HSF1) and scaffold attachment factor B (SAFB). During chronic stress, the persistent association of RBM45 with NSBs leads to the formation of large, insoluble nuclear RBM45 inclusions. RBM45 nuclear inclusions persist after stressor removal and NSB disassembly and the inclusions resemble the nuclear RBM45 pathology seen in ALS, FTLD, and AD. We also quantified the cell type- and disease-specific patterns of RBM45 pathology in ALS, FTLD, AD, and non-neurologic disease control subjects. RBM45 nuclear and cytoplasmic inclusions are found in neurons and glia in ALS, FTLD, and AD but not in controls. Across diseases, RBM45 nuclear inclusion pathology occurs more frequently than cytoplasmic RBM45 inclusion pathology and exhibits cell type-specific variation. Collectively, our results define new stress-associated functions of RBM45, a mechanism for its nuclear aggregation and inclusion formation, a role for NSBs in the pathogenesis of diseases such as ALS, FTLD, and AD, and further underscore the importance of self-association to both the normal and pathological functions of RBPs in these diseases.

neuroscience↗

bioRxiv2019

Blood-spinal cord barrier leakage is not caused by neurodegeneration in amyotrophic lateral sclerosis

BackgroundAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease involving progressive degeneration of upper and lower motor neurons. Both lower motor neuron loss and the deposition of phosphorylated TDP-43 inclusions display regional patterning along the spinal cord. The blood-spinal cord barrier (BSCB) ordinarily restricts entry into the spinal cord parenchyma of blood components that are neurotoxic, but in ALS there is evidence for barrier breakdown. Here we sought to examine whether BSCB breakdown, motor neuron loss, and TDP-43 proteinopathy display the same regional patterning across and along the spinal cord.\n\nMethodsWe measured cerebrospinal fluid (CSF) hemoglobin in living ALS patients (n=87 controls, n=236 ALS) as a potential biomarker of BSCB and blood-brain barrier leakage. We then immunostained cervical, thoracic, and lumbar post mortem spinal cord tissue (n=5 controls, n=13 ALS) and employed semi-automated imaging and analysis to quantify and map lower motor neuron loss and phosphorylated TDP-43 inclusion load against hemoglobin leakage.\n\nResultsMotor neuron loss and TDP-43 proteinopathy were seen at all three levels of the ALS spinal cord, with most abundant TDP-43 deposition in the ventral grey (lamina IX) of the cervical and lumbar cord. In contrast, hemoglobin leakage was observed along the ALS spinal cord axis but was most severe in the dorsal grey and white matter in the thoracic spinal cord.\n\nConclusionsOur data show that leakage of the blood-spinal cord barrier occurs during life but at end-stage its distribution is independent from the major motor neuron pathology and is unlikely to be a major contributor to pathogenesis in ALS.

neuroscience↗

bioRxiv2019

Glycolysis upregulation is neuroprotective as a compensatory mechanism in ALS

Amyotrophic Lateral Sclerosis (ALS), is a fatal neurodegenerative disorder, with TDP-43 inclusions as a major pathological hallmark. Using a Drosophila model of TDP-43 proteinopathy we found significant alterations in glucose metabolism including increased pyruvate, suggesting that modulating glycolysis may be neuroprotective. Indeed, a high sugar diet improves locomotor and lifespan defects caused by TDP-43 proteinopathy in motor neurons or glia, but not muscle, suggesting that metabolic dysregulation occurs in the nervous system. Overexpressing human glucose transporter GLUT-3 in motor neurons mitigates TDP-43 dependent defects in synaptic vesicle recycling and improves locomotion. Furthermore, PFK mRNA, a key indicator of glycolysis, is upregulated in flies and patient derived iPSC motor neurons with TDP-43 pathology. Surprisingly, PFK overexpression rescues TDP-43 induced locomotor deficits. These findings from multiple ALS models show that mechanistically, glycolysis is upregulated in degenerating motor neurons as a compensatory mechanism and suggest that increased glucose availability is protective.

neuroscience↗