Journal articles
Yang YHC, Briant LJB, Raab CA, Mullapudi ST, Maischein H-M, Kawakami K, Stainier DYR (2022). Innervation modulates the functional connectivity between pancreatic endocrine cells.
Elife,
11Abstract:
Innervation modulates the functional connectivity between pancreatic endocrine cells.
The importance of pancreatic endocrine cell activity modulation by autonomic innervation has been debated. To investigate this question, we established an in vivo imaging model that also allows chronic and acute neuromodulation with genetic and optogenetic tools. Using the GCaMP6s biosensor together with endocrine cell fluorescent reporters, we imaged calcium dynamics simultaneously in multiple pancreatic islet cell types in live animals in control states and upon changes in innervation. We find that by 4 days post fertilization in zebrafish, a stage when islet architecture is reminiscent of that in adult rodents, prominent activity coupling between beta cells is present in basal glucose conditions. Furthermore, we show that both chronic and acute loss of nerve activity result in diminished beta-beta and alpha-beta activity coupling. Pancreatic nerves are in contact with all islet cell types, but predominantly with beta and delta cells. Surprisingly, a subset of delta cells with detectable peri-islet neural activity coupling had significantly higher homotypic coupling with other delta cells suggesting that some delta cells receive innervation that coordinates their output. Overall, these data show that innervation plays a vital role in the maintenance of homotypic and heterotypic cellular connectivity in pancreatic islets, a process critical for islet function.
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MacDonald AJ, Yang YHC, Cruz AM, Beall C, Ellacott KLJ (2021). Brain-Body Control of Glucose Homeostasis—Insights from Model Organisms.
Frontiers in Endocrinology,
12Abstract:
Brain-Body Control of Glucose Homeostasis—Insights from Model Organisms
Tight regulation of blood glucose is essential for long term health. Blood glucose levels are defended by the correct function of, and communication between, internal organs including the gastrointestinal tract, pancreas, liver, and brain. Critically, the brain is sensitive to acute changes in blood glucose level and can modulate peripheral processes to defend against these deviations. In this mini-review we highlight select key findings showcasing the utility, strengths, and limitations of model organisms to study brain-body interactions that sense and control blood glucose levels. First, we discuss the large platform of genetic tools available to investigators studying mice and how this field may yet reveal new modes of communication between peripheral organs and the brain. Second, we discuss how rats, by virtue of their size, have unique advantages for the study of CNS control of glucose homeostasis and note that they may more closely model some aspects of human (patho)physiology. Third, we discuss the nascent field of studying the CNS control of blood glucose in the zebrafish which permits ease of genetic modification, large-scale measurements of neural activity and live imaging in addition to high-throughput screening. Finally, we briefly discuss glucose homeostasis in drosophila, which have a distinct physiology and glucoregulatory systems to vertebrates.
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White SA, Zhang LS, Pasula DJ, Yang YHC, Luciani DS (2020). Bax and Bak jointly control survival and dampen the early unfolded protein response in pancreatic β-cells under glucolipotoxic stress.
Sci Rep,
10(1).
Abstract:
Bax and Bak jointly control survival and dampen the early unfolded protein response in pancreatic β-cells under glucolipotoxic stress.
ER stress and apoptosis contribute to the loss of pancreatic β-cells under pro-diabetic conditions of glucolipotoxicity. Although activation of canonical intrinsic apoptosis is known to require pro-apoptotic Bcl-2 family proteins Bax and Bak, their individual and combined involvement in glucolipotoxic β-cell death are not known. It has also remained an open question if Bax and Bak in β-cells have non-apoptotic roles in mitochondrial function and ER stress signaling, as suggested in other cell types. Using mice with individual or combined β-cell deletion of Bax and Bak, we demonstrated that glucolipotoxic β-cell death in vitro occurs by both non-apoptotic and apoptotic mechanisms, and the apoptosis could be triggered by either Bax or Bak alone. In contrast, they had non-redundant roles in mediating staurosporine-induced apoptosis. We further established that Bax and Bak do not affect normal glucose-stimulated β-cell Ca2+ responses, insulin secretion, or in vivo glucose tolerance. Finally, our experiments revealed that combined deletion of Bax and Bak amplified the unfolded protein response in islets during the early stages of chemical- or glucolipotoxicity-induced ER stress. These findings shed new light on roles of the core apoptosis machinery in β-cell survival and stress signals of importance for the pathobiology of diabetes.
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Yang YHC, Briant LJB, Raab C, Mullapudi ST, Maischein H-M, Kawakami K, Stainier DYR (2020). Innervation modulates the functional connectivity between pancreatic endocrine cells.
Abstract:
Innervation modulates the functional connectivity between pancreatic endocrine cells
AbstractDirect modulation of pancreatic endocrine cell activity by autonomic innervation has been debated. To resolve this question, we established an in vivo imaging model which also allows chronic and acute neuromodulation. Starting at a stage when zebrafish islet architecture is reminiscent of that in adult rodents, we imaged calcium dynamics simultaneously in multiple islet cell types. We first find that activity coupling between beta cells increases upon glucose exposure. Surprisingly, glucose exposure also increases alpha-alpha, alpha-beta and beta-delta coordination. We further show that both chronic and acute loss of nerve activity diminish activity coupling, as observed upon gap junction depletion. Notably, chronic loss of innervation severely disrupts delta cell activity, suggesting that delta cells receive innervation which coordinates its output. Overall, these data show that innervation plays a vital role in the establishment and maintenance of homotypic and heterotypic cellular connectivity in pancreatic islets, a process critical for islet function.
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Mullapudi ST, Boezio GLM, Rossi A, Marass M, Matsuoka RL, Matsuda H, Helker CSM, Yang YHC, Stainier DYR (2019). Disruption of the pancreatic vasculature in zebrafish affects islet architecture and function.
Development,
146(21).
Abstract:
Disruption of the pancreatic vasculature in zebrafish affects islet architecture and function.
A dense local vascular network is crucial for pancreatic endocrine cells to sense metabolites and secrete hormones, and understanding the interactions between the vasculature and the islets may allow for therapeutic modulation in disease conditions. Using live imaging in two models of vascular disruption in zebrafish, we identified two distinct roles for the pancreatic vasculature. At larval stages, expression of a dominant negative version of Vegfaa (dnVegfaa) in β-cells led to vascular and endocrine cell disruption with a minor impairment in β-cell function. In contrast, expression of a soluble isoform of Vegf receptor 1 (sFlt1) in β-cells blocked the formation of the pancreatic vasculature and drastically stunted glucose response, although islet architecture was not affected. Notably, these effects of dnVegfaa or sFlt1 were not observed in animals lacking vegfaa, vegfab, kdrl, kdr or flt1 function, indicating that they interfere with multiple ligands and/or receptors. In adults, disrupted islet architecture persisted in dnVegfaa-expressing animals, whereas sFlt1-expressing animals displayed large sheets of β-cells along their pancreatic ducts, accompanied by impaired glucose tolerance in both models. Thus, our study reveals novel roles for the vasculature in patterning and function of the islet.
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Yang YHC, Kawakami K, Stainier DYR (2018). A new mode of pancreatic islet innervation revealed by live imaging in zebrafish.
eLife,
7Abstract:
A new mode of pancreatic islet innervation revealed by live imaging in zebrafish
Pancreatic islets are innervated by autonomic and sensory nerves that influence their function. Analyzing the innervation process should provide insight into the nerve-endocrine interactions and their roles in development and disease. Here, using in vivo time-lapse imaging and genetic analyses in zebrafish, we determined the events leading to islet innervation. Comparable neural density in the absence of vasculature indicates that it is dispensable for early pancreatic innervation. Neural crest cells are in close contact with endocrine cells early in development. We find these cells give rise to neurons that extend axons toward the islet as they surprisingly migrate away. Specific ablation of these neurons partly prevents other neurons from migrating away from the islet resulting in diminished innervation. Thus, our studies establish the zebrafish as a model to interrogate mechanisms of organ innervation, and reveal a novel mode of innervation whereby neurons establish connections with their targets before migrating away.
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Mullapudi ST, Helker CS, Boezio GL, Maischein H-M, Sokol AM, Guenther S, Matsuda H, Kubicek S, Graumann J, Yang YHC, et al (2018). Screening for insulin-independent pathways that modulate glucose homeostasis identifies androgen receptor antagonists.
Elife,
7Abstract:
Screening for insulin-independent pathways that modulate glucose homeostasis identifies androgen receptor antagonists.
Pathways modulating glucose homeostasis independently of insulin would open new avenues to combat insulin resistance and diabetes. Here, we report the establishment, characterization, and use of a vertebrate 'insulin-free' model to identify insulin-independent modulators of glucose metabolism. insulin knockout zebrafish recapitulate core characteristics of diabetes and survive only up to larval stages. Utilizing a highly efficient endoderm transplant technique, we generated viable chimeric adults that provide the large numbers of insulin mutant larvae required for our screening platform. Using glucose as a disease-relevant readout, we screened 2233 molecules and identified three that consistently reduced glucose levels in insulin mutants. Most significantly, we uncovered an insulin-independent beneficial role for androgen receptor antagonism in hyperglycemia, mostly by reducing fasting glucose levels. Our study proposes therapeutic roles for androgen signaling in diabetes and, more broadly, offers a novel in vivo model for rapid screening and decoupling of insulin-dependent and -independent mechanisms.
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Matsuda H, Mullapudi ST, Yang YHC, Masaki H, Hesselson D, Stainier DYR (2018). Whole-Organism Chemical Screening Identifies Modulators of Pancreatic β-Cell Function.
Diabetes,
67(11), 2268-2279.
Abstract:
Whole-Organism Chemical Screening Identifies Modulators of Pancreatic β-Cell Function
β-Cell loss and dysfunction play a critical role in the progression of type 1 and type 2 diabetes. Identifying new molecules and/or molecular pathways that improve β-cell function and/or increase β-cell mass should significantly contribute to the development of new therapies for diabetes. Using the zebrafish model, we screened 4,640 small molecules to identify modulators of β-cell function. This in vivo strategy identified 84 stimulators of insulin expression, which simultaneously reduced glucose levels. The insulin promoter activation kinetics for 32 of these stimulators were consistent with a direct mode of action. A subset of insulin stimulators, including the antidiabetic drug pioglitazone, induced the coordinated upregulation of gluconeogenic pck1 expression, suggesting functional response to increased insulin action in peripheral tissues. Notably, Kv1.3 inhibitors increased β-cell mass in larval zebrafish and stimulated β-cell function in adult zebrafish and in the streptozotocin-induced hyperglycemic mouse model. In addition, our data indicate that cytoplasmic Kv1.3 regulates β-cell function. Thus, using whole-organism screening, we have identified new small-molecule modulators of β-cell function and glucose metabolism.
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Yang YHC, Wills QF, Johnson JD (2015). A live-cell, high-content imaging survey of 206 endogenous factors across five stress conditions reveals context-dependent survival effects in mouse primary beta cells. Diabetologia, 58(6), 1239-1249.
Szabat M, Modi H, Ramracheya R, Girbinger V, Chan F, Lee JTC, Piske M, Kamal S, Carol Yang YH, Welling A, et al (2015). High-content screening identifies a role for Na. <sup>+</sup>. channels in insulin production.
Royal Society Open Science,
2(12), 150306-150306.
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High-content screening identifies a role for Na. +. channels in insulin production
. Insulin production is the central feature of functionally mature and differentiated pancreatic
. β
. -cells. Reduced insulin transcription and dedifferentiation have been implicated in type 2 diabetes, making drugs that could reverse these processes potentially useful. We have previously established ratiometric live-cell imaging tools to identify factors that increase insulin promoter activity and promote
. β
. -cell differentiation. Here, we present a single vector imaging tool with eGFP and mRFP, driven by the
. Pdx1
. and
. Ins1
. promoters, respectively, targeted to the nucleus to enhance identification of individual cells in a high-throughput manner. Using this new approach, we screened 1120 off-patent drugs for factors that regulate
. Ins1
. and
. Pdx1
. promoter activity in MIN6
. β
. -cells. We identified a number of compounds that positively modulate
. Ins1
. promoter activity, including several drugs known to modulate ion channels. Carbamazepine was selected for extended follow-up, as our previous screen also identified this use-dependent sodium channel inhibitor as a positive modulator of
. β
. -cell survival. Indeed, carbamazepine increased
. Ins1
. and
. Ins2
. mRNA in primary mouse islets at lower doses than were required to protect
. β
. -cells. We validated the role of sodium channels in insulin production by examining Nav1.7 (
. Scn9a
. ) knockout mice and remarkably islets from these animals had dramatically elevated insulin content relative to wild-type controls. Collectively, our experiments provide a starting point for additional studies aimed to identify drugs and molecular pathways that control insulin production and
. β
. -cell differentiation status. In particular, our unbiased screen identified a novel role for a
. β
. -cell sodium channel gene in insulin production.
.
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Chan MT, Lim GE, Skovsø S, Yang YHC, Albrecht T, Alejandro EU, Hoesli CA, Piret JM, Warnock GL, Johnson JD, et al (2014). Effects of insulin on human pancreatic cancer progression modeled in vitro. BMC Cancer, 14(1).
Yang YHC, Vilin YY, Roberge M, Kurata HT, Johnson JD (2014). Multiparameter Screening Reveals a Role for Na+ Channels in Cytokine-Induced β-Cell Death. Molecular Endocrinology, 28(3), 406-417.
Rezania A, Bruin JE, Arora P, Rubin A, Batushansky I, Asadi A, O'Dwyer S, Quiskamp N, Mojibian M, Albrecht T, et al (2014). Reversal of diabetes with insulin-producing cells derived in vitro from human pluripotent stem cells. Nature Biotechnology, 32(11), 1121-1133.
Yang YHC, Manning Fox JE, Zhang KL, MacDonald PE, Johnson JD (2013). Intraislet SLIT–ROBO signaling is required for beta-cell survival and potentiates insulin secretion.
Proceedings of the National Academy of Sciences,
110(41), 16480-16485.
Abstract:
Intraislet SLIT–ROBO signaling is required for beta-cell survival and potentiates insulin secretion
Significance
.
. There is an unmet need for factors that can protect pancreatic islet beta cells from apoptosis and improve insulin secretion in the context of diabetes. There are many candidate factors produced locally in islets. We investigated the role of axon guidance factors and found that the SLIT–Roundabout receptors system is present, where it responds to stress. Full expression of SLIT ligands is essential for optimal beta-cell survival. Recombinant SLIT promotes survival and increases insulin secretion via mechanisms involving Ca
. 2+
. and actin.
.
Abstract.
Yang YHC, Johnson JD (2013). Multi-parameter, single-cell, kinetic analysis reveals multiple modes of cell death in primary pancreatic beta-cells.
Journal of Cell ScienceAbstract:
Multi-parameter, single-cell, kinetic analysis reveals multiple modes of cell death in primary pancreatic beta-cells
Programmed β-cell death plays an important role in both type 1 and type 2 diabetes. Most of what is known about the mechanisms of β-cell death comes from single time-point, single parameter measurements of bulk populations of mixed cells. Such approaches are inadequate for determining the true extend of the heterogeneity in death mechanisms. Here, we characterized the timing and order of molecular events associated with cell death in single β-cells under multiple diabetic stress conditions, including hyperglycemia, cytokine exposure, nutrient deprivation and ER stress. We simultaneously measured the kinetics of six distinct cell death mechanisms by using a caspase-3 sensor and three vital dyes, together with bright field imaging. We identified several cell death modes where the order of events that define apoptosis was not observed. This was termed ‘partial apoptosis’. Remarkably, complete classical apoptosis, defined as cells with plasma membrane blebbing, caspase-3 activity, nuclear condensation and membrane annexinV labeling prior to loss of plasma membrane integrity, was found in only half of cytokine-treated primary β-cells and never in cells stressed by serum removal. On the other hand, MIN6 cell death was almost exclusively via complete classical apoptosis. Ambient glucose modulated the cell death mode and kinetics in primary β-cells. Together, our data define the kinetic progression of β-cell death mechanisms under different conditions and illustrate the heterogeneity and plasticity of cell death modes in β-cells. We conclude that apoptosis is not the primary mode of adult primary β-cell death.
Abstract.
Yang YHC, Johnson JD (2012). Multi-parameter Live Cell Tracking of Apoptotic and Non-apoptotic Beta-cell Death: High-content Screening for Factors that Prevent Beta-cell Apoptosis. Canadian Journal of Diabetes, 36(5).
Son E, Kim J-J, Lim YW, Au-Yeung TT, Yang CYH, Breuil C (2011). Diversity and decay ability of basidiomycetes isolated from lodgepole pines killed by the mountain pine beetle.
Canadian Journal of Microbiology,
57(1), 33-41.
Abstract:
Diversity and decay ability of basidiomycetes isolated from lodgepole pines killed by the mountain pine beetle
When lodgepole pines ( Pinus contorta Douglas ex Louden var. latifolia Engelm. ex S. Watson) that are killed by the mountain pine beetle ( Dendroctonus ponderosae ) and its fungal associates are not harvested, fungal decay can affect wood and fibre properties. Ophiostomatoids stain sapwood but do not affect the structural properties of wood. In contrast, white or brown decay basidiomycetes degrade wood. We isolated both staining and decay fungi from 300 lodgepole pine trees killed by mountain pine beetle at green, red, and grey stages at 10 sites across British Columbia. We retained 224 basidiomycete isolates that we classified into 34 species using morphological and physiological characteristics and rDNA large subunit sequences. The number of basidiomycete species varied from 4 to 14 species per site. We assessed the ability of these fungi to degrade both pine sapwood and heartwood using the soil jar decay test. The highest wood mass losses for both sapwood and heartwood were measured for the brown rot species Fomitopsis pinicola and the white rot Metulodontia and Ganoderma species. The sap rot species Trichaptum abietinum was more damaging for sapwood than for heartwood. A number of species caused more than 50% wood mass losses after 12 weeks at room temperature, suggesting that beetle-killed trees can rapidly lose market value due to degradation of wood structural components.
Abstract.
Szabat M, Kalynyak TB, Lim GE, Chu KY, Yang YH, Asadi A, Gage BK, Ao Z, Warnock GL, Piret JM, et al (2011). Musashi expression in β-cells coordinates insulin expression, apoptosis and proliferation in response to endoplasmic reticulum stress in diabetes. Cell Death & Disease, 2(11), e232-e232.
Yang YHC, Szabat M, Bragagnini C, Kott K, Helgason CD, Hoffman BG, Johnson JD (2011). Paracrine signalling loops in adult human and mouse pancreatic islets: netrins modulate beta cell apoptosis signalling via dependence receptors. Diabetologia, 54(4), 828-842.
Hill JA, Szabat M, Hoesli CA, Gage BK, Yang YHC, Williams DE, Riedel MJ, Luciani DS, Kalynyak TB, Tsai K, et al (2010). A Multi-Parameter, High-Content, High-Throughput Screening Platform to Identify Natural Compounds that Modulate Insulin and Pdx1 Expression. PLoS ONE, 5(9), e12958-e12958.
