Biology subjects

Gu, G.

Publications and source records attributed to Gu, G..

At least 19 recordsLinked to original sources

bioRxiv2026

Copine-6 integrates calcium, phosphoinositide and Rab11 signals to coordinate glutamate receptor recycling

Endosomal trafficking is a major pathway that delivers cell-surface proteins, including glutamate receptors, to support neurotransmission and normal brain functions. Activity-dependent insertion of glutamate receptors is essential for synaptic plasticity, learning and memory. Copine-6 is a neuronal-specific calcium (Ca2+) binding protein that mediates activity-induced exocytosis of -amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptors. The activation of N-methyl-D-aspartate (NMDA) receptors triggers Ca2+-dependent translocation of Copine-6 to intracellular endosomal compartments. However, the mechanisms underlying the activity-dependent accumulation of Copine-6 in endosomes remain unknown. Here, we show that Copine-6 exhibits Ca2+-dependent binding to phosphatidylinositol-3-phosphate (PI(3)P) through the C2B domain and displays enhanced interaction with active Rab11a in a Ca2+-independent manner via the vWA domain. Mutations in the C2B that inhibit binding to PI(3)P not only block the activity-induced translocation of Copine-6 to early endosomes, but it also causes an aberrant accumulation of Copine-6 in recycling endosomes. Consequently, loss of Copine-6 expression impairs the efficient coupling of early and recycling endosomes and blocks activity-dependent delivery of both AMPA and NMDA receptors onto the neuronal plasma membrane. These defects can be restored by re-expressing wild-type Copine-6, but not the C2B phospholipid-binding mutant. Together, our findings establish Copine-6 as a molecular bridge that enhances coupling between the early and recycling endosomal membranes, thereby facilitating the activity-dependent forward trafficking of glutamate receptors to the neuronal plasma membrane to maintain synaptic potentiation.

cell biology↗

bioRxiv2025

Deregulated Myt3 translation predisposes islet β-cells to dysfunction under obesity-induced metabolic stress

In response to obesity-related metabolic stress, islet {beta}-cells adapt (or compensate) by increasing their secretory function and mass. Yet, for unknown reasons, this compensation is reversed in some individuals at some point to induce {beta}-cell failure and overt type 2 diabetes (T2D). We have previously shown that transcription factor Myt3 (St18) and its paralogs, Myt1 and Myt2, prevent {beta}-cell failure. Myt3 was induced at post-transcriptional levels by obesity-related stress in both mouse and human {beta} cells and its downregulation accompanied {beta}-cell dysfunction during T2D development. Single-nucleotide polymorphisms in MYT3 were associated with an increased risk of developing human diabetes. We now demonstrate that Myt3 translation is regulated by an upstream open-reading frame that overlaps with the main Myt3 open-reading frame in mice. Disrupting this overlap enhances Myt3 translation in mouse {beta} cells without metabolic stress but decreases it under high-fat-diet challenges. Consequently, this deregulation results in {beta}-cell dysfunction and glucose intolerance in mice, accompanied by compromised expression of several {beta}-cell function genes. These findings suggest that stress-induced Myt3 translation is part of the compensation mechanism that prevents {beta}-cell failure.

genetics↗

bioRxiv2025

A Comprehensive Workflow for Imaging Live Insulin Secretion Events and Granules in Intact Islets

Accurate detection of insulin secretion from pancreatic beta cells is crucial for understanding normal physiological insulin secretion and its pathophysiological counterpart in diabetic states. Traditional methods using fluorescently labeled insulin granules or dye labeling often struggle to distinguish secretion from insulin granule dynamics. We present an optimized protocol using the cell-impermeable Zn2+-binding dye FluoZin-3, which fluoresces upon Zn2+ co-secretion with insulin outside of the islet, more accurately representing secretion. FluoZin-3 combined with intact islet attachment to vascular extracellular matrix and TIRF microscopy offers high spatial and temporal resolution as well as a high signal-to-noise ratio in a minimally perturbed system. Additionally, by integrating the cell-permeable Zn2+-binding dye ZIGIR, we can track insulin granule dynamics alongside secretion events. Our approach generates large datasets, which we efficiently analyze using ilastik machine learning software, enabling fast, accurate, and optionally supervised analysis. This technique builds on our groups previous protocols, detailing a streamlined workflow adaptable to high-resolution, live-cell microscopy for not just insulin but other secretory/granule systems as well. With this method, we investigated secretion behavior of different IG pools in real time during the first phase of insulin secretion: predocked, which appear before high glucose stimulation and are docked at the membrane; docked, which appear upon high glucose stimulation and dock at the membrane; and newcomer, which appear upon high glucose stimulation but dont dock at the membrane. The predocked and newcomer insulin granules are equally secreted and newcomer insulin granules dwell less than one second before secretion upon high glucose stimulation. The predocked and docked insulin granules, however, stay longer at the membrane before secretion. This method is useful for the investigation of functional beta cell heterogeneity of insulin granule secretion in space and time.

cell biology↗

bioRxiv2025

Myelin transcription factors 1 and 3 have overlapping but distinct roles in insulin secretion and survival of human β cells

Aims/hypothesisGenetic and environmental factors work together to cause islet beta-cell failure, leading to type 2 diabetes (T2D). How these factors are integrated to regulate beta cells remains largely unclear. Based on our previous findings that the family of Myelin transcription factors (MYT1, MYT1L, and ST18) prevents mouse beta-cell failure by repressing the overactivation of stress response, their regulation by obesity-related nutrition signals in human beta cells, and their association with T2D, we postulate that these factors prevent human beta-cell failure under normal physiology and obesity-related stress. MethodsMYT1 or ST18 were knocked down in primary human beta cells using shRNA. Beta-cell survival, secretory function, and gene expression were examined after islet cells were cultured in vitro or xenotransplanted into mice under normal or obesity-related stress. ResultsIn culture, MYT1-knockdown (KD) caused beta-cell death, while ST18-KD compromised glucose-stimulated insulin secretion. Under obesity-induced stress as xenotransplants, ST18-KD also caused beta-cell death. Accordingly, MYT1-KD deregulated several genes and genesets in cell death and cellular stress response, while ST18-KD deregulated those regulating stress response, mitochondria, and ion channels. Corresponding to these gene expression changes, ST18-KD reduces glucose-stimulated Ca2+ influx in beta cells. In addition, the MYT1- and ST18-regulated genes are enriched for T2D-associated loci, with an enrichment of 2.05-fold relative to random distribution. Conclusions/interpretationThe MYT TFs complement each other to integrate genetic and environmental factors to prevent beta-cell failure and T2D, with their major effects exerted on beta-cell viability and/or Ca2+ influx. Graphical AbstractNutrient-responsive transcription factors MYT1 and ST18 regulate human beta-cell survival and secretory functions. Under low metabolic stress, MYT1 regulates cell survival while ST18 regulates insulin secretion. Under high metabolic stress, ST18 also regulates beta-cell survival. MYT1, at least partly, regulates cell survival through stress-related apoptotic processes, while ST18 regulates insulin secretion via Ca2+ influx. Research in context summaryO_ST_ABSBackgroundC_ST_ABSO_LIThe myelin transcription factors (MYT TFs, including MYT1, MYT1l, and ST18) prevent mouse beta-cell failure by depressing the overactivation of stress-response genes. C_LIO_LISNPs in all three MYT loci are associated with human type 2 diabetes. C_LIO_LIThe expression and nuclear localization of MYT1 and ST18 were increased in primary human beta cells under acute metabolic stress but downregulated in type 2 diabetes. C_LIO_LIThe co-knockdown of MYT1, MYT1L, and ST18 in a human beta-cell line resulted in apoptosis. C_LI Key questionO_LIHow does MYT1 or ST18 regulate human beta-cell function and survival? C_LI New findingsO_LIMYT1 prevents human beta-cell death under normal and metabolic stress conditions, corresponding to deregulation of a few genes involved in cell death under cellular stress. C_LIO_LIST18 promotes insulin secretion under normal physiological conditions by regulating Ca2+ influx and prevents beta-cell death under metabolic stress. C_LIO_LIThe MYT1- and ST18-regulated genes are enriched for type 2 diabetes-risk loci. C_LI Clinical impactO_LIRegulators of the MYT-TF activities could be explored to delay/prevent beta-cell failure and the development of type 2 diabetes. C_LI

cell biology↗

bioRxiv2024

Directed insulin secretion occurs at precise cortical regions with optimal ELKS content that are devoid of microtubules

To maintain normal blood glucose levels, pancreatic beta cells secrete insulin into the bloodstream at specialized regions at the cell periphery, often called secretion hot spots. While many secretory machinery components are located all over the cell membrane, directed secretion relies on distinct cortical patches of the scaffolding protein ELKS and the microtubule (MT)-anchoring protein LL5{beta}. However, using TIRF microscopy of intact mouse islets to precisely localize secretion events within ELKS/LL5{beta} patches, we now show that secretion is restricted to only 5% of ELKS/LL5{beta} patch area. Moreover, the majority of secretion occurs at the margins of ELKS patches. This suggests that additional factor(s) must be responsible for hot spot definition. Because the MT cytoskeleton plays a regulatory role in the insulin secretion process via both delivery and removal of secretory granules from the secretion sites, we test whether local MT organization defines secretory activity at hot spots. We find that the majority of secretion events occur at regions devoid of MTs. Based on our findings, we present a model in which local MT disassembly and optimal ELKS content are strong predictors of directed insulin secretion. Significance StatementO_LIInsulin has to be secreted directly into the bloodstream for efficient regulation of glucose metabolism. Molecular requirements for precise secretion location and microtubule-mediated regulation in directed secretion are uncharacterized. C_LIO_LIUsing intact mouse islets and a live insulin secretion assay, we demonstrate that cortical patches containing ELKS and LL5{beta} display secretory heterogeneity and secretion hot spots are precisely localized to patch edges that are devoid of microtubules. C_LIO_LIThese findings suggest that microtubule absence is critical for secretion and secretion occurs away from presumed sites of secretory granule delivery. This expands the current knowledge of regulation and spatial characteristics of insulin secretion. C_LI

cell biology↗

bioRxiv2024

Pancreatic islet alpha cells regulate microtubule stability in neighboring beta cells to tune insulin secretion and induce functional heterogeneity in individual mouse and human islets

We have reported that the microtubule (MT) network in {beta} cells attenuates this function by withdrawing insulin secretory granules (ISGs) away from the plasma membrane. Thus, high glucose-induced MT remodeling is required for robust glucose-stimulated insulin secretion (GSIS). We now show that -cell secreted hormones, Gcg and/or Glp1, regulate the MT stability in {beta} cells. Activating the receptors of Gcg or Glp1 (GcgR or Glp1R) with chemical agonists induces MT destabilization in {beta} ells in the absence of high glucose. In contrast, inhibiting these receptors with antagonists attenuates high glucose-induced MT destabilization. Supporting the significance of this regulation, the MT networks in {beta} cells of islets with higher /{beta} cell ratio are less stable than those with lower /{beta} cell ratio. Within each individual islet, {beta} cells that are located close to cells show faster MTs remodeling upon glucose stimulation than those away. Consequently, islets with higher /{beta} cell ratio secrete more insulin in response to high glucose and plasma membrane depolarization, which is recapitulated by direct Gcg stimulation. These combined results reveal a new MT-dependent pathway by which cells, using Gcg and or Glp1-mediated paracrine signaling, tune {beta}-cell secretion. In addition, the different -{beta} cell ratios in individual islets lead to their heterogeneous secretory responses, which may be important for handling secretory function needs under different physiological conditions. HighlightsO_LIGcg sensitizes glucose-induced MT remodeling in mouse and human {beta} cells C_LIO_LIMT density in single islets anti-correlates with /{beta} cell ratio C_LIO_LIGSIS levels in single islets positively correlate with /{beta} cell ratio C_LIO_LIDifferent /{beta} cell ratio contributes to heterogeneity of single islet GSIS C_LI

cell biology↗

bioRxiv2024

Uncovering Individualized Cerebellar Atrophy Pattern and Behavioral Links in Children with Brainstem Tumor

Background and PurposeBrainstem tumors are rare but cause enduring behavioral issues, challenging patients and surgeons. Research on cerebellar changes in these patients limited, despite symptoms similar to cerebellar injuries. This study aims to investigate cerebellar damage pattern resulting from brainstem tumors and its association with behavioral disorders. MethodsIn this study, a U-Net-based segmentation algorithm was used to divide the cerebellum into 26 lobules, which were then used to build a normative model for assessing individual structural deviations. Furthermore, a behavior prediction model was developed using the total outlier count (tOC) index and brain volume as predictive features. ResultsMost patients were found to have negative deviations in cerebellar regions, particularly in anterior lobules like Left V. Higher tOC was significantly associated with severe social problems (r = 0.31, p = 0.001) and withdrawal behavior (r = 0.28, p = 0.001). Smaller size of cerebellar regions strongly correlated with more pronounced social problems (r = 0.27, p = 0.007) and withdrawal behavior (r = 0.25, p = 0.015). Notably, lobules Right X, V, IV, VIIB, Left IX, VIII, and X influenced social problems, while Left V, Right IV, Vermis VI, and VIII impacted withdrawal behavior. ConclusionsOur study revealed cerebellar damage patterns in patients with brainstem tumors, emphasizing the role of both anterior and posterior cerebellar lobes in social problems and withdrawal behavior. This research sheds light on the brain mechanisms underlying complex behavioral disorders in brainstem tumor patients.

neuroscience↗

bioRxiv2024

Atf4 protects islet beta-cell identity and function under acute glucose-induced stress but promotes beta-cell failure in the presence of free fatty acid

Glucolipotoxicity, caused by combined hyperglycemia and hyperlipidemia, results in {beta}-cell failure and type 2 diabetes (T2D) via cellular stress-related mechanisms. Activating transcription factor 4 (Atf4) is an essential effector of stress response. We show here that Atf4 expression in {beta}-cells is dispensable for glucose homeostasis in young mice, but it is required for {beta}-cell function during aging and under obesity-related metabolic stress. Henceforth, aged Atf4-deficient {beta}-cells display compromised secretory function under acute hyperglycemia. In contrast, they are resistant to acute free fatty acid-induced loss-of identity and dysfunction. At molecular level, Atf4-deficient {beta}-cells down-regulate genes involved in protein translation, reducing {beta}-cell identity gene products under high glucose. They also upregulate several genes involved in lipid metabolism or signaling, likely contributing to their resistance to free fatty acid-induced dysfunction. These results suggest that Atf4 activation is required for {beta}-cell identity and function under high glucose, but this paradoxically induces {beta}-cell failure in the presence of high levels of free fatty acids. Different branches of Atf4 activity could be manipulated for protecting {beta}-cells from metabolic stress-induced failure. HighlightsO_LIAtf4 is dispensable in {beta}-cells in young mice C_LIO_LIAtf4 protects {beta}-cells under high glucose C_LIO_LIAtf4 exacerbate fatty acid-induced {beta}-cell defects C_LIO_LIAtf4 activates translation but depresses lipid-metabolism C_LI

genetics↗

bioRxiv2024

ELO-6 expression predicts longevity in isogenic populations of Caenorhabditis elegans

Variations of individual lifespans within genetically identical populations in homogenous environments are remarkable, with the cause largely unknown. Gene expression changes with age, and the transcriptome changes correlate with chronological aging. Here, we show that in Caenorhabditis elegans, the expression dynamic of the fatty acid elongase ELO-6 during aging predicts individual longevity in isogenic populations. The expression of elo-6 is reduced with age. From adult day 5, ELO-6 expression level exhibits variation between individuals, and the expression level is positively correlated with adult lifespan and health span. Interventions that prolong longevity enhance the expression stability of ELO-6 during aging from adult day 4 to adult day 8, indicating ELO-6 is also a populational lifespan predictor. We performed transcriptome analysis in short-lived and long-lived isogenic worms and identified differentially expressed genes, which are enriched for PQM-1 binding sites. Decreasing pqm-1 expression in young adults improved the homogeneity of ELO-6 levels between individuals and enhanced health span. Furthermore, we found reducing the expression of genes that are highly expressed in short-lived individuals, including PQM-1 target genes, enhanced ELO-6 expression stability with age and extended lifespan. Thus, our study identified ELO-6 as a predictor of individual and populational lifespan and revealed the role of pqm-1 in restricting health span and possibly causing individual lifespan variation.

physiology↗

bioRxiv2023

Glucose-stimulated KIF5B-driven microtubule sliding organizes microtubule networks in pancreatic beta cells

In pancreatic islet {beta} cells, molecular motors use cytoskeletal polymers microtubules as tracks for intracellular transport of insulin secretory granules. The {beta}-cell microtubule network has a complex architecture and is non-directional, which provides insulin granules at the cell periphery for rapid secretion response, yet to avoid over-secretion and subsequent hypoglycemia. We have previously characterized a peripheral sub-membrane microtubule array, which is critical for the withdrawal of excessive insulin granules from the secretion sites. Microtubules in {beta} cells originate at the Golgi in the cell interior, and how the peripheral array is formed is unknown. Using real-time imaging and photo-kinetics approaches in clonal mouse pancreatic {beta} cells MIN6, we now demonstrate that kinesin KIF5B, a motor protein with a capacity to transport microtubules as cargos, slides existing microtubules to the cell periphery and aligns them to each other along the plasma membrane. Moreover, like many physiological {beta}-cell features, microtubule sliding is facilitated by a high glucose stimulus. These new data, together with our previous report that in high glucose sub-membrane MT array is destabilized to allow for robust secretion, indicate that MT sliding is another integral part of glucose-triggered microtubule remodeling, likely replacing destabilized peripheral microtubules to prevent their loss over time and {beta}-cell malfunction.

cell biology↗

bioRxiv2022

Protective human anti-poxvirus monoclonal antibodies are generated from rare memory B cells isolated by multicolor antigen tetramers

Smallpox, an epidemic disease caused by Orthopoxvirus variola, was eradicated worldwide through immunization. The immunization against smallpox was discontinued in 1980. However, incidences of monkeypox virus infection in humans have occurred sporadically, and there is also great fear that engineered forms of poxvirus could be used as biological weapons. Therefore, monoclonal antibodies against poxvirus are in urgent need for the detection and treatment of poxvirus infection. The vaccinia virus extracellular envelope protein A33 is a potential candidate for subunit vaccine. We used multi-fluorescence-labeled tetrameric A33 antigen to identify rare poxvirus specific memory B cells from PBMC of volunteers with vaccinia virus immunization more than 40 years ago. Despite extremely low frequencies of the poxvirus specific memory B cells, we successfully sorted A33 tetramer-labeled single memory B cells and reconstructed antibodies with single-cell RT-PCR of the B-cell receptor. Among the monoclonal antibodies, one clone H2 exhibited high specificity and affinity with A33. H2 efficiently inhibited viral infection and spread in cells. Passive immunotherapy of H2 in mice protected mice from lethal infection when administered either prophylactically or therapeutically. These results suggest the potential of the anti-A33 human antibody-based detection and therapeutics for poxvirus infection.

immunology↗

bioRxiv2022

The microtubule minus end-binding protein CAMSAP2 does not regulate microtubule dynamics in primary pancreatic β-cells but facilitates insulin secretion

Glucose stimulation induces the remodeling of microtubules in Islet {beta}-cells to potentiate glucose-stimulated insulin secretion. CAMSAP2 is a microtubule minus-end binding protein and is reported to stabilize and position microtubules in several non-{beta}-cells, such as human retinal pigment epithelium cells. In immortalized insulinoma MIN6 cells, CAMSAP2 binds to and forms short stretches at microtubule minus ends in the cytoplasm, which is consistent with the reported subcellular localization and functions of CAMSAP2 in non-{beta}-cells. Surprisingly, we found that CAMSAP2 expressed in primary islet {beta}-cells does not form short stretches in the cytoplasm, but instead is localized to the Golgi apparatus. This novel localization is specific to {beta}-but not -cells in islets and it is independent of MT-binding. Knockdown of CAMSAP2 by shRNA impairs Golgi-ER trafficking, reduces total insulin content, and attenuates GSIS without affecting the MT dynamics or releasability of insulin granules in islet {beta}-cells. Corresponding to these results, we found that primary islets and MIN6 cells express different CAMSAP2 isoforms. We propose that primary islet {beta} cells use a novel CAMSAP2 isoform for a MT-independent non-canonical function, which is to promote Golgi-ER trafficking that supports efficient production of insulin secretory granules.

cell biology↗

bioRxiv2022

3D Printable High Performance Conducting Polymer Hydrogel for All-Hydrogel Bioelectronics

Owing to the unique combination of electrical conductivity and tissue-like mechanical properties, conducting polymer hydrogels have emerged as a promising candidate for bioelectronic interfacing with biological systems. However, despite the recent advances, the development of hydrogels with both excellent electrical and mechanical properties in physiological environments remains a lingering challenge. Here, we report a bi-continuous conducting polymer hydrogel (BC-CPH) that simultaneously achieves high electrical conductivity (over 11 S cm-1), stretchability (over 400%) and fracture toughness (over 3,300 J m-2) in physiological environments, and is readily applicable to advanced fabrication methods including 3D printing. Enabled by the BC-CPH, we further demonstrate multi-material 3D printing of monolithic all-hydrogel bioelectronic interfaces for long-term electrophysiological recording and stimulation of various organs. This study may offer promising materials and a platform for future bioelectronic interfacing.

bioengineering↗

bioRxiv2021

St18 specifies globus pallidus projection neuron identity in MGE lineage

The medial ganglionic eminence (MGE) is a progenitor domain in the subpallium that produces both locally-projecting interneurons which undergo tangential migration in structures such as the cortex as well as long-range projection neurons that occupy subcortical nuclei. Very little is known about the transcriptional mechanisms specifying the migratory behavior and axonal projection patterns of these two broad classes of MGE-derived neurons. In this study, we identify St18 as a novel transcriptional determinant specifying projection neuron fate in the MGE lineage. St18 is transiently expressed in the MGE subventricular zone (SVZ) and mantle, and we assessed its function using an ES cell-based model of MGE development. Induction of St18 is sufficient to direct ES-derived MGE neurons to adopt a projection neuron-like identity as defined by migration and morphology. Using genetic loss-of-function in mice, we find that St18 is required for the production of globus pallidus pars externa (GPe) prototypic projection neurons. Single cell RNA sequencing revealed that St18 regulates MGE output of specific neuronal populations: in the absence of St18, we observe a large expansion of cortical interneurons at the expense of putative GPe neurons. Through gene expression analysis we identified a downstream effector of St18, Cbx7, which is a component of Polycomb repressor complex 1. We find that Cbx7 is essential for projection neuron-like migration and is not involved in St18-mediated projection neuron-like morphology. Our results characterize a novel transcriptional determinant that directs GPe prototypic projection neuron identity. Further, we identified a downstream target of St18, Cbx7, which regulates only the migratory behavior of long-range projection neurons, suggesting that specific features of MGE projection neuron identity may be governed in a compartmentalized fashion by distinct transcriptional modules downstream of St18.

developmental biology↗

bioRxiv2021

Auto-qPCR: A Python based web app for automated and reproducible analysis of qPCR data

Quantifying changes in DNA and RNA levels is essential in numerous molecular biology protocols. Quantitative real time PCR (qPCR) techniques have evolved to become commonplace, however, data analysis includes many time-consuming and cumbersome steps, which can lead to mistakes and misinterpretation of data. To address these bottlenecks, we have developed an open-source Python software to automate processing of result spreadsheets from qPCR machines, employing calculations usually performed manually. Auto-qPCR is a tool that saves time when computing qPCR data, helping to ensure reproducibility of qPCR experiment analyses. Our web-based app (https://auto-q-pcr.com/) is easy to use and does not require programming knowledge or software installation. Using Auto-qPCR, we provide examples of data treatment, display and statistical analyses for four different data processing modes within one program: (1) DNA quantification to identify genomic deletion or duplication events; (2) assessment of gene expression levels using an absolute model, and relative quantification (3) with or (4) without a reference sample. Our open access Auto-qPCR software saves the time of manual data analysis and provides a more systematic workflow, minimizing the risk of errors. Our program constitutes a new tool that can be incorporated into bioinformatic and molecular biology pipelines in clinical and research labs.

molecular biology↗

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

TRPM7 is a critical regulator of pancreatic endocrine development and high-fat diet-induced β-cell proliferation.

The melastatin subfamily of the transient receptor potential channels (TRPM) are regulators of pancreatic {beta}-cell function. TRPM7 is the most abundant islet TRPM channel; however, the role of TRPM7 in {beta}-cell function has not been determined. Here, we utilized various spatiotemporal transgenic mouse models to investigate how TRPM7 knockout influences pancreatic endocrine development, proliferation, and function. Ablation of TRPM7 within pancreatic progenitors reduced pancreatic size, as well as -cell and {beta}-cell mass. This resulted in impaired glucose tolerance due to decreased serum insulin levels. However, ablation of TRPM7 following endocrine specification or in adult mice did not impact endocrine expansion or glucose tolerance. As TRPM7 regulates cell proliferation, we assessed how TRPM7 influences {beta}-cell hyperplasia under insulin resistant conditions. {beta}-cell proliferation induced by high-fat diet was significantly decreased in TRPM7 deficient {beta}-cells. The endocrine roles of TRPM7 may be influenced by cation flux through the channel, and indeed we find that TRPM7 ablation alters {beta}-cell intracellular Mg2+. Together, these findings reveal that TRPM7 controls pancreatic progenitor expansion and {beta}-cell proliferation, which is likely due to regulation of Mg2+ homeostasis. SummaryThis manuscript identifies a critical developmental role for TRPM7 channels in pancreatic progenitor cells. The manuscript also determines that TRPM7 plays a key role in {beta}-cell proliferation under insulin-resistant conditions.

developmental biology↗

bioRxiv2020

Microtubules regulate pancreatic beta cell heterogeneity via spatiotemporal control of insulin secretion hot spots

Heterogeneity of glucose-stimulated insulin secretion (GSIS) in pancreatic islets is physiologically important but poorly understood. Here, we utilize whole mouse islets to determine how microtubules affect secretion toward the vascular extracellular matrix. Our data indicate that microtubule stability in the {beta}-cell population is heterogenous, and that cells with more stable microtubules secrete less in response to a stimulus. Consistently, microtubule hyper-stabilization prevents, and microtubule depolymerization promotes {beta}-cell activation. Analysis of spatiotemporal patterns of secretion events shows that microtubule depolymerization activates otherwise dormant {beta}-cells via initiation of secretion clusters (hot spots). Microtubule depolymerization also enhances secretion from individual cells, introducing both additional clusters and scattered events. Interestingly, without microtubules, the timing of clustered secretion is dysregulated, extending the first phase of GSIS. Our findings uncover a novel microtubule function in tuning insulin secretion hot spots, which leads to accurately measured and timed response to glucose stimuli and promotes functional {beta}-cell heterogeneity.

cell biology↗