Biology subjects

Hu, R.

Publications and source records attributed to Hu, R..

At least 91 records · Page 5Linked to original sources

bioRxiv2021

The genomic formation of Tanka people, an isolated 'Gypsies in water' in the coastal region of Southeast China

ObjectivesThree different hypotheses proposed via the controversial evidence from cultural, anthropological and uniparental genetic analysis respectively stated that Tanka people probably originated from Han Chinese, ancient Baiyue tribe, or the admixture of them. Therefore, the genetic origin and admixture history of the Tanka people, an isolated "Gypsies in water" in the coastal region of Southeast China, are needed to be genetically clarified. Materials and methodsTo elucidate the genetic origin of the Southeast Tanka people and explore their genetic relationship with surrounding indigenous Tai-Kadai and Austronesian people and Neolithic-to-historic ancients from the Yellow River Basin (YRB) and Fujian, we conducted a large-scale population genomic study among 1498 modern and ancient Eurasians, in which 73 Tanka and 4 Han people were first reported here. Both allele-shared and haplotype-based statistical methods were used here, including PCA, ADMIXTURE, f-statistics, ALDER, qpGraph-/TreeMix and qpAdm/qpWave, ChromoPainter and FineSTRUCTURE ResultsWe found a specific genetic cline in PCA plots and detected the Tanka-specific homogeneous ancestry in model-based ADMIXTURE results, suggesting differentiated demographic history between Tanka and surrounding Hans. Formal tests based on sharing allele patterns showed a close relationship between Tanka people and Han Chinese, but the Tanka population harbored more southern East Asian ancestry related to Austronesian and Tai-Kadai people compared with southern Hans. Besides, the reconstructed differentiated demographic history revealed that southern Xinshizhou Tanka harbored more ancestry related to the Tai-Kadai or coastal ancient Neolithic to Bronze Age East Asians compared with northern Shacheng Tanka. The qpGraph-/TreeMix-based phylogenetic framework, qpAdm/qpWave-based admixture modeling and FineSTRUCTURE-based dendrogram among ancient northern and southern East Asians further demonstrated that the primary ancestry of modern Tanka derived from ancient millet farmers in the YRB with additional admixture from multiple southern East Asian sources. DiscussionSharing ancestry estimated from the f-statistics and sharing haplotypic landscape inferred from the ChromoPainter and FineSTRUCTURE showed that Southeast Tanka people not only had a close genetic relationship with both Northern Hans and YRB millet farmers but also possessed more southern East Asian ancestry related to Austronesian, Tai-Kadai and Hmong-Mien people. Our genomic data and fitted admixture models supported modern Tanka originated from ancient North China and obtained additional gene flow from ancient southern East Asians in the processes of southward migrations.

genetics↗

bioRxiv2021

In Vivo Simultaneous Nonlinear Absorption Raman and Fluorescence (SNARF) Imaging of Mouse Brain Cortical Structures

AO_SCPLOWBSTRACTC_SCPLOWTwo-photon excited fluorescence (TPEF) microscopy is a widely used optical imaging technique that has revolutionized neurophotonics through a diverse palette of dyes, specialized transgenic models, easy implementation, and straightforward data analysis. However, in vivo TPEF imaging is often limited in the number of contrasts available to distinguish different cells, structures, or functions. We propose using two label-free multiphoton microscopy techniques - stimulated Raman scattering (SRS) microscopy and transient absorption microscopy (TAM) - as complementary and orthogonal imaging modalities to TPEF for in vivo brain imaging. In this study, we construct a simultaneous nonlinear absorption, Raman, and fluorescence (SNARF) microscope and image several cortical structures up to 250-300 m below the pial surface, the highest reported in vivo imaging depth for SRS or TAM. We further demonstrate the capabilities of our SNARF microscope through the quantification of age-dependent myelination, hemodynamics, vessel structure, cell density, and cell identity in vivo. Using machine learning, we report the use of label-free SRS and TAM features to predict capillary-lining cell identities with 90% accuracy. The SNARF microscope and methodology outlined herein provide a powerful platform to study several research topics, including neurovascular coupling, blood-brain barrier, neuronal and axonal degeneration in aging, and neurodegenerative diseases.

neuroscience↗

bioRxiv2021

Quantitative imaging of intracellular density with ratiometric stimulated Raman scattering microscopy

Cell size and density impact a wide range of physiological functions, including tissue homeostasis, growth regulation, and osmoregulation. Both are tightly regulated in mammalian cells. In comparison, density variation of a given cell type is much smaller than cell size, indicating that maintenance of cell type-specific density is important for cell function. Despite this importance, little is known about how cell density affects cell function and how it is controlled. Current tools for intracellular cell density measurements are limited either to suspended cells or cells growing on 2D substrates, neither of which recapitulate the physiology of single cells in intact tissue. While optical measurements have the potential to measure cell density in situ and noninvasively, light scattering in multicellular systems prevents direct quantification. Here, we introduce an intracellular density imaging technique based on ratiometric stimulated Raman scattering microscopy (rSRS). It quantifies intracellular drymass density through vibrational imaging of macromolecules. Moreover, water is used as an internal standard to correct for aberration and light scattering. We demonstrate real-time measurement of intracellular density quantification and show that density is tightly regulated across different cell types and can be used to differentiate cell types as well as cell states. We further demonstrate dynamic imaging of density change in response to osmotic challenge as well as intracellular density imaging of a 3D tumor spheroid. Our technique has the potential for imaging intracellular density in intact tissue and understanding density regulation and its role in tissue homeostasis.

biophysics↗

bioRxiv2021

Three-dimensional organization of chromatin associated RNAs and their role in chromatin architecture in human cells

The interphase genome is dynamically organized in the nucleus and decorated with chromatin-associated RNA (caRNA). It remains unclear whether the genome architecture modulates the spatial distribution of caRNA and vice versa. Here, we generate a resource of genome-wide RNA-DNA and DNA-DNA contact maps in human cells. These maps reveal the chromosomal domains demarcated by locally transcribed RNA, hereafter termed RNA-defined chromosomal domains. Further, the spreading of caRNA is constrained by the boundaries of topologically associating domains (TADs), demonstrating the role of the 3D genome structure in modulating the spatial distribution of RNA. Conversely, stopping transcription or acute depletion of RNA induces thousands of chromatin loops genome-wide. Activation or suppression of the transcription of specific genes suppresses or creates chromatin loops straddling these genes. Deletion of a specific caRNA-producing genomic sequence promotes chromatin loops that straddle the interchromosomal target sequences of this caRNA. These data suggest a feedback loop where the 3D genome modulates the spatial distribution of RNA, which in turn affects the dynamic 3D genome organization.

genomics↗

bioRxiv2021

Homogeneous environmental selection overturns distance-decay relationship of soil prokaryotic community

Though being fundamental to global diversity distribution, little is known about the geographic pattern of soil microorganisms across different biomes on a large scale. Here, we investigated soil prokaryotic communities from Chinese northern grasslands on a scale up to 4,000 km in both alpine and temperate biomes. Surprisingly, prokaryotic similarities increased with geographic distance after tipping points of 1,760 - 1,920 km, overturning the well-accepted distance-decay relationship and generating a significant U-shape pattern. Such U-shape pattern was likely due to decreased disparities in environmental heterogeneity along with geographic distance when across biomes, as homogeneous environmental selection dominated prokaryotic assembly based on {beta}NTI analysis. Consistently, short-term environmental heterogeneity also followed the U-shape pattern spatially, mainly attributed to dissolved nutrients. In sum, these results demonstrate that homogeneous environmental selection via dissolved nutrients overwhelmed the "distance" effect when across biomes, subverting the previously well-accepted geographic pattern for microbes on a large scale.

ecology↗

bioRxiv2021

Fluorescence-Activated Droplet Sorting of Polyethylene terephthalate Degrading Enzymes

Enzymes that can decompose synthetic plastics such as polyethylene terephthalate (PET) are urgently needed. However, a bottleneck remains due to a lack of techniques for detecting and sorting environmental microorganisms with vast diversity and abundance. Here, we developed a fluorescence-activated droplet sorting (FADS) pipeline for high-throughput screening of PET-degrading microorganisms or enzymes (PETases). The pipeline comprises three steps: generation and incubation of droplets encapsulating single cells, picoinjection of fluorescein dibenzoate (FDBz) as the fluorogenic probe, and screening of droplets to obtain PET-degrading cells. We characterized critical factors associated with this method, including specificity and sensitivity for discriminating PETase from other enzymes. We then optimized its performance and compatibility with environmental samples. The system was used to screen a wastewater sample from a PET textile mill. We successfully obtained PET-degrading species from nine different genera. Moreover, two putative PETases from isolates Kineococcus endophyticus Un-5 and Staphylococcus epidermidis Un-C2-8 were genetically derived, heterologously expressed, and preliminarily validated for PET-degrading activities. We speculate that the FADS pipeline can be widely adopted to discover new PET-degrading microorganisms and enzymes in various environments and may be utilized in the directed evolution of PETases using synthetic biology.

microbiology↗

bioRxiv2021

Topologically Associating Domain Boundaries are Commonly Required for Normal Genome Function

Topologically associating domain (TAD) boundaries are thought to partition the genome into distinct regulatory territories. Anecdotal evidence suggests that their disruption may interfere with normal gene expression and cause disease phenotype1-3, but the overall extent to which this occurs remains unknown. Here we show that TAD boundary deletions commonly disrupt normal genome function in vivo. We used CRISPR genome editing in mice to individually delete eight TAD boundaries (11-80kb in size) from the genome in mice. All deletions examined resulted in at least one detectable molecular or organismal phenotype, which included altered chromatin interactions or gene expression, reduced viability, and anatomical phenotypes. For 5 of 8 (62%) loci examined, boundary deletions were associated with increased embryonic lethality or other developmental phenotypes. For example, a TAD boundary deletion near Smad3/Smad6 caused complete embryonic lethality, while a deletion near Tbx5/Lhx5 resulted in a severe lung malformation. Our findings demonstrate the importance of TAD boundary sequences for in vivo genome function and suggest that noncoding deletions affecting TAD boundaries should be carefully considered for potential pathogenicity in clinical genetics screening.

genomics↗

bioRxiv2021

Visual temporal integration by multi-level regularities fosters the emergence of dynamic conscious experience

The relationship between information integration and visual awareness is central to contemporary theories and research on human consciousness. While there is evidence that humans are adept at integrating spatially structured information to form a coherent conscious percept, to date, little is known about how we integrate visual information over time based on its temporal structure and whether such temporal integration process contributes to our awareness of the dynamic world. Using binocular rivalry, we demonstrated that a diverse set of structured visual streams, constituted either by idiom, shape, or motion stimuli, predominated over their non-structured but otherwise matched counterparts in the competition for conscious access. Despite the apparent resemblance, there was a substantial dissociation of these observed privileges between the semantic- and perceptual-level structures, specifically regarding their resistance to spatiotemporal perturbations and demands for conscious processing over the visual integration process. These findings corroborate the essential role of structure-guided information integration in the generation of conscious content and highlight temporal integration by multi-level regularities as a fundamental mechanism to foster the emergence of continuous conscious experience.

neuroscience↗

bioRxiv2021

Genetic diversity, evolutionary dynamics and pathogenicity of ferret badger rabies virus variants in mainland China, 2008-2018

In contrast to dog associated human rabies cases decline year by year due to the rabies vaccination coverage rates increase in China, ferret badger (FB, Melogale moschata)-associated human rabies cases emerged in the 1990s, and are now an increasingly recognized problem in southeast China. To investigate epidemiology, temporal evolution dynamics, transmission characterization and pathogenicity of FB-associated rabies viruses (RABVs), from 2008 to 2018, we collected 3,622 FB brain samples in Jiangxi and Zhejiang Province, and detected 112 RABV isolates. Four FB-related lineages were identified by phylogenetic analysis (lineages A-D), the estimated Times to Most Recent Common Ancestor were 1941, 1990, 1937 and 1997 for lineages A-D respectively. Furthermore, although no FB-associated human rabies case has been reported there apart from Wuyuan area, FB-RABV isolates are mainly distributed in Jiangxi Province. Pathogenicity of FB-RABVs was assessed using peripheral inoculation in mice and in beagles with masseter muscles, mortality-rates ranging from 20% to 100% in mice and 0 to 20% in beagles in the groups infected with the various isolates. Screening of sera from humans with FB bites and no postexposure prophylaxis to rabies, revealed that 5 of 9 were positive for neutralizing antibodies of RABV. All the results above indicated that FB-RABV variants caused a lesser pathogenicity in mice, beagles and even humans. Vaccination in mice suggests that inactivated vaccine or recombinant subunit vaccine products can be used to control FB- associated rabies, however, oral vaccines for stray dogs and wildlife need to be developed and licensed in China urgently. IMPORTANCEIn recent years FB-associated rabies virus has been identified as a major life-threatening pathogen in some districts in China. To understand the risk to public health and the contemporary dynamics, the present study conducted extensive investigations on FB rabies, distribution, virus isolation, phylogeny analysis, pathogenicity determination of various FB rabies virus strains, besides, serologic epidemiology survey to those whom bit by FB was also collected. The results show that the majority of FBs dwell in southeast China, like Jiangxi and Zhejiang Province, Phylogenetic analysis indicates that all isolated FB RABVs evolved from dogs, and the FB RABV can separate into 4 distinct lineages distributed relatively independent in different areas. The isolate strains differ in pathogenicity, although they have relatively lower pathogenicity compared to dog rabies virus according to our study, the need for further study to licensed oral vaccines and FB RABV pathogenesis is emphasized in order to control rabies.

pathology↗

bioRxiv2021

MLL3/MLL4 Histone Methyltranferase Activity Dependent Chromatin Organization at Enhancers during Embryonic Stem Cell Differentiation

MLL3 (KMT2C) and MLL4 (KMT2D), the major mono-methyltransferases of histone H3 lysine 4 (H3K4), are required for cellular differentiation and embryonic development in mammals. We previously observed that MLL3/4 promote long-range chromatin interactions at enhancers, however, it is still unclear how their catalytic activities contribute to enhancer-dependent gene activation in mammalian cell differentiation. To address this question, we mapped histone modifications, long-range chromatin contacts as well as gene expression in MLL3/4 catalytically deficient mouse embryonic stem (ES) cells undergoing differentiation toward neural precursor cells. We showed that MLL3/4 activities are responsible for deposition of H3K4me1 modification and formation of long-range enhancer-promoter contacts at a majority of putative enhancers gained during cell differentiation, but are dispensable for most candidate enhancers found in undifferentiated ES cells that persist through differentiation. While transcriptional induction at most genes is unaltered in the MLL3/4 catalytically deficient cells, genes making more contacts with MLL3/4-dependent putative enhancers are disproportionately affected. These results support that MLL3/4 contributes to cellular differentiation through histone-methyltransferase-activity dependent induction of enhancer-promoter contacts and transcriptional activation at a subset of lineage-specific genes.

cell biology↗

bioRxiv2021

Parallel Characterization of cis-Regulatory Elements for Multiple Genes UsingCRISPRpath

Current pooled CRISPR screens for cis-regulatory elements (CREs) can only accommodate one gene based on its expression level. Here, we describe CRISPRpath, a scalable screening strategy for parallelly characterizing CREs of genes linked to the same biological pathway and converging phenotypes. We demonstrate the ability of CRISPRpath for simultaneously identifying functional enhancers of six genes in the 6-thioguanine-induced DNA mismatch repair pathway using both CRISPR interference (CRISPRi) and CRISPR nuclease (CRISPRn) approaches. 60% of the identified enhancers are known promoters with distinct epigenomic features compared to other active promoters, including increased chromatin accessibility and interactivity. Furthermore, by imposing different levels of selection pressure, CRISPRpath can distinguish enhancers exerting strong impact on gene expression from those exerting weak impact. Our results offer a nuanced view of cis-regulation and demonstrate that CRISPRpath can be leveraged for understanding the complex gene regulatory program beyond transcriptional output at scale.

genomics↗

bioRxiv2021

Discovery and Functional Characterization of Pro-growth Enhancers in Human Cancer Cells

Precision medicine depends critically on developing treatment strategies that can selectively target cancer cells with minimal adverse effects. Identifying unique transcriptional regulators of oncogenic signaling, and targeting cancer-cell-specific enhancers that may be active only in specific tumor cell lineages, could provide the necessary high specificity, but a scarcity of functionally validated enhancers in cancer cells presents a significant hurdle to this strategy. We address this limitation by carrying out large-scale functional screens for pro-growth enhancers using highly multiplexed CRISPR-based perturbation and sequencing in multiple cancer cell lines. We used this strategy to identify 488 pro-growth enhancers in a colorectal cancer cell line and 22 functional enhancers for the MYC and MYB key oncogenes in an additional nine cancer cell lines. The majority of pro-growth enhancers are accessible and presumably active only in cancer cells but not in normal tissues, and are enriched for elements associated with poor prognosis in colorectal cancer. We further identify master transcriptional regulators and demonstrate that the cancer pro-growth enhancers are modulated by lineage-specific transcription factors acting downstream of growth signaling pathways. Our results uncover context-specific, potentially actionable pro-growth enhancers from cancer cells, yielding insight into altered oncogenic transcription and revealing potential therapeutic targets for cancer treatment.

cancer biology↗

bioRxiv2021

Sex Differences in Solute and Water Handling in the Human Kidney: Modeling and Functional Implications

Besides the excretion of metabolic wastes, the kidneys regulate homeostasis of electrolytes, pH, metabolites, volume and blood pressure. Sex differences in kidney function and blood pressure have been widely described across many species. Immunoblot analysis has revealed that the kidney of a female rat is not simply a smaller version of a male kidney. Rather, male and female rat kidneys exhibit dimorphic patterns of transporter expression and salt handling, the functional implications of which have been analyzed in a series of previously published modeling studies of rat kidney function. In the present study, we extend the analysis to the human kidney: we developed sex-specific models of solute and water transport in the human kidney, and identified epithelial transport parameters, consistent with patterns found in male and female rats, that yield urine output and excretion rates consistent with known human values. The model predicts that the lower sodium hydrogen exchanger 3 (NHE3) activity in women reduces the fractional reabsorption of Na+, K+, Cl-, and water along the proximal tubule, compared to men, and that the larger load on the distal nephron can be handled by enhanced activities in key Na+ transporter such as epithelial sodium channel (ENaC) and sodium chloride cotransporter (NCC) in women. Model simulations further indicate that the larger distal transport capacity and proximal transport reserve may better prepare women for elevated demands of pregnancy and lactation. The larger distal transport capacity may also contribute to reduced efficacy of angiotensin converting enzyme inhibitors to lower blood pressure in women. Author summaryThe kidneys maintain homeostasis by controlling the amount of water, ions, and other substances in the blood. That function is accomplished by the nephrons, which transform glomerular filtrate into urine by an exquisite transport process mediated by a number of membrane transporters. Recently, the distribution of renal transporters along the nephron has been shown to be markedly different between male and female rodents. We postulate that similar sexual dimorphism exists between men and women, and we seek to reveal its physiological implications. We hypothesize that the larger abundance of a renal Na+ transport in the proximal tubules in females may also better prepare them for the fluid retention adaptations required during pregnancy and lactation, durint which renal and systemic hemodynamics are both drastically altered by the marked volume expansion and vasodilation. Also, kidneys play a key role in blood pressure regulation, and a popular class of anti-hypertensive medications, angiotensin converting enzymes (ACE) inhibitors, have been reported to be less effective in women. Model simulations suggest that the blunted natriuretic and diuretic effects of ACE inhibition in women can be attributed, in part, to their higher distal baseline transport capacity.

physiology↗

bioRxiv2020

Hsp70 chaperons TDP-43 in dynamic, liquid-like phase and prevents it from amyloid aggregation

TAR DNA binding protein 43 kDa (TDP-43) undergoes liquid-liquid phase separation (LLPS) and forms reversible, cytoprotective nuclear bodies (NBs) in response to stress in cells. Abnormal liquid-to-solid phase transition condenses TDP-43 into irreversible pathological fibrils, which is associated with neurodegenerative disorders including amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD). However, the mechanisms how cells maintain the dynamics of TDP-43 NBs in stressed conditions are not well understood. Here, we show that the molecular chaperon heat shock protein 70 (Hsp70) is recruited into TDP-43 NBs in stressed cells. It co-phase separates with TDP-43 and delays the maturation of TDP-43 droplets in vitro. In cells, downregulation of Hsp70 not only diminishes the formation but also reduces the dynamics of TDP-43 NBs especially during prolonged stress, which potentiates the cytotoxicity of TDP-43. Using NMR, we reveal that Hsp70 binds to the highly aggregation-prone, transient -helix of TDP-43 via its nucleotide-binding domain, which keeps TDP-43 in the highly dynamic, liquid-like phase and prevents pathological aggregation of TDP-43 both in vitro and in cells. Collectively, our findings demonstrate a crucial role of Hsp70 in chaperoning TDP-43 in the liquid-like phase, which provides a novel layer of the molecular mechanism how chaperons help proteins to remain functional and protect cells from stressed and/or diseased conditions.

cell biology↗

bioRxiv2020

Cortical entrainment to hierarchical contextual rhythms recomposes dynamic attending in visual perception

Temporal regularity is ubiquitous and essential to guiding attention and coordinating behavior within a dynamic environment. Previous researchers have modeled attention as an internal rhythm that may entrain to first-order regularity from rhythmic events to prioritize information selection at specific time points. Using the attentional blink paradigm, here we show that higher-order regularity based on rhythmic organization of contextual features (pitch, color, or motion) may serve as a temporal frame to recompose the dynamic profile of visual temporal attention. Critically, such attentional reframing effect is well predicted by cortical entrainment to the higher-order contextual structure at the delta band as well as its coupling with the stimulus-driven alpha power. These results suggest that the human brain involuntarily exploits multiscale regularities in rhythmic contexts to recompose dynamic attending in visual perception, and highlight neural entrainment as a central mechanism for optimizing our conscious experience of the world in the time dimension.

neuroscience↗

bioRxiv2020

Genomic Insights into the Demographic History of Southern Chinese

Southern China is the birthplace of rice-cultivating agriculture, different language families, and human migrations that facilitated these cultural diffusions. The fine-scale demographic history in situ, however, remains unclear. To comprehensively cover the genetic diversity in East and Southeast Asia, we generated genome-wide SNP data from 211 present-day Southern Chinese and co-analyzed them with more than 1,200 ancient and modern genomes. We discover that the previously described Southern East Asian or Yangtze River Farmer lineage is monophyletic but not homogeneous, comprising four regionally differentiated sub-ancestries. These ancestries are respectively responsible for the transmission of Austronesian, Kra-Dai, Hmong-Mien, and Austroasiatic languages and their original homelands successively distributed from East to West in Southern China. Multiple phylogenetic analyses support that the earliest living branching among East Asian-related populations is First Americans ([~]27,700 BP), followed by the pre-LGM differentiation between Northern and Southern East Asians ([~]23,400 BP) and the pre-Neolithic split between Coastal and Inland Southern East Asians ([~]16,400 BP). In North China, distinct coastal and inland routes of south-to-north gene flow had established by the Holocene, and further migration and admixture formed the genetic profile of Sinitic speakers by [~]4,000 BP. Four subsequent massive migrations finalized the complete genetic structure of present-day Southern Chinese. First, a southward Sinitic migration and the admixture with Kra-Dai speakers formed the Sinitic Cline. Second, a bi-directional admixture between Hmong-Mien and Kra-Dai speakers gave rise to the Hmong-Mien Cline in the interior of South China between [~]2,000 and [~]1,000 BP. Third, a southwestward migration of Kra-Dai speakers in recent [~]2,000 years impacted the genetic profile for the majority of Mainland Southeast Asians. Finally, an admixture between Tibeto-Burman incomers and indigenous Austroasiatic speakers formed the Tibeto-Burman speakers in Southeast Asia by [~]2,000 BP.

genomics↗

bioRxiv2020

Microtubules and Gαo-signaling independently regulate the preferential secretion of newly synthesized insulin granules in pancreatic islet β cells

For sustainable function, each pancreatic islet {beta} cell maintains thousands of insulin granules (IGs) at all times. Glucose stimulation induces the secretion of a small portion of these IGs and simultaneously triggers IG biosynthesis to sustain this stock. The failure of these processes, often induced by sustained high-insulin output, results in type 2 diabetes. Intriguingly, newly synthesized IGs are more likely secreted during glucose-stimulated insulin secretion. The older IGs tend to lose releasability and be degraded, which represents a futile metabolic load that can sensitize {beta} cells to workload-induced dysfunction and even death. Here, we examine the factor(s) that allows the preferential secretion of younger IGs. We show that {beta} cells without either microtubules (MTs) or Go signaling secrete a bigger portion of older IGs, which is associated with increased IG docking on plasma membrane. Yet Go inactivation does not alter the {beta}-cell MT network. These findings suggest that Go and MT regulate the preferential release of newer IGs via parallel pathways and provide two potential models to further explore the underlying mechanisms and physiological significance of this regulation in functional {beta} cells.

cell biology↗

bioRxiv2020

CHMP2B regulates TDP-43 phosphorylation and proteotoxicity via modulating CK1 turnover independent of the autophagy-lysosomal pathway

Protein inclusions containing phosphorylated TDP-43 are a shared pathology in several neurodegenerative diseases including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, most ALS/FTD patients do not have a mutation in TDP-43 or the enzymes directly regulating its phosphorylation. It is intriguing how TDP-43 becomes hyperphosphorylated in each disease condition. In a genetic screen for novel TDP-43 modifiers, we found that knockdown (KD) of CHMP2B, a key component of the endosomal sorting complex required for transport (ESCRT) machinery, suppressed TDP-43-mediated neurodegeneration in Drosophila. Further investigation using mammalian cells indicated that CHMP2B KD decreased whereas its overexpression (OE) increased TDP-43 phosphorylation levels. Moreover, a known FTD-causing mutation CHMP2Bintron5 promoted hyperphosphorylation, insolubility and cytoplasmic accumulation of TDP-43. Interestingly, CHMP2B did not manifest these effects by its well-known function in the autophagy-lysosomal pathway. Instead, the kinase CK1 tightly regulated TDP-43 phosphorylation level in cells, and CHMP2B OE or CHMP2BIntron5 significantly decreased ubiquitination and the turnover of CK1 via the ubiquitin-proteasome (UPS) pathway. Finally, we showed that CHMP2B protein levels increased in the cerebral cortices of aged mice, which might underlie the age-associated TDP-43 pathology and disease onset. Together, our findings reveal a molecular link between the two ALS/FTD-pathogenic proteins CHMP2B and TDP-43, and provide an autophagy-independent mechanism for CHMP2B in pathogenesis. SIGNIFICANCE STATEMENTTDP-43 and CHMP2B are both ALS/FTD-associated proteins. Protein aggregations containing phosphorylated TDP-43 are a pathological hallmark of ALS/FTD; however, it is unclear how increased phosphorylation of TDP-43 occurs in diseases. The pathogenesis of CHMP2B has mainly been considered as a consequence of autophagy-lysosomal dysfunction. Here, we reveal that increase of CHMP2B levels (which occurs in aged mouse brains) or expression of the disease-causing mutation CHMP2BIntron5 promotes TDP-43 hyperphosphorylation, insolubility and cytoplasmic mislocalization. This effect is independent of the autophagy-lysosomal pathway but rather relies on the proteasome-mediated turnover of the kinase CK1 that phosphorylates TDP-43. Together, we provide a new molecular mechanism of CHMP2B pathogenesis by linking it to TDP-43 pathology via CK1.

neuroscience↗