Developmental beta-cell death orchestrates the islet's inflammatory milieu by regulating immune system crosstalk.

While pancreatic beta-cell proliferation has been extensively studied, the role of cell death during islet development remains incompletely understood. Using a genetic model of caspase inhibition in beta cells coupled with mathematical modeling, we here discover an onset of beta-cell death in juvenile zebrafish, which regulates beta-cell mass. Histologically, this beta-cell death is underestimated due to phagocytosis by resident macrophages.

Fluorescent Tagging of Endogenous FOXO for Live Imaging and Pull-Down Assays.

Proteins are the major and most diverse biomolecules, directing all activities of a cell. For this reason, visualizing protein expression, localization, and dynamics is fundamental in biology. In most cases, protein visualization relies on the overexpression of fluorescently tagged proteins which may not recapitulate endogenous expression pattern and dynamics.

PTPRK regulates glycolysis and de novo lipogenesis to promote hepatocyte metabolic reprogramming in obesity.

Fat accumulation, de novo lipogenesis, and glycolysis are key drivers of hepatocyte reprogramming and the consequent metabolic dysfunction-associated steatotic liver disease (MASLD). Here we report that obesity leads to dysregulated expression of hepatic protein-tyrosine phosphatases (PTPs). PTPRK was found to be increased in steatotic hepatocytes in both humans and mice, and correlates positively with PPARγ-induced lipogenic signaling.

Optogenetic β cell interrogation in vivo reveals a functional hierarchy directing the Ca response to glucose supported by vitamin B6.

Coordination of cellular activity through Ca enables β cells to secrete precise quantities of insulin. To explore how the Ca response is orchestrated in space and time, we implement optogenetic systems to probe the role of individual β cells in the glucose response. By targeted β cell activation/inactivation in zebrafish, we reveal a hierarchy of cells, each with a different level of influence over islet-wide Ca dynamics.

Starvation-resistant cavefish reveal conserved mechanisms of starvation-induced hepatic lipotoxicity.

Starvation causes the accumulation of lipid droplets in the liver, a somewhat counterintuitive phenomenon that is nevertheless conserved from flies to humans. Much like fatty liver resulting from overfeeding, hepatic lipid accumulation (steatosis) during undernourishment can lead to lipotoxicity and atrophy of the liver. Here, we found that although surface populations of undergo this evolutionarily conserved response to starvation, the starvation-resistant cavefish larvae of the same species do not display an accumulation of lipid droplets upon starvation.

Starvation resistant cavefish reveal conserved mechanisms of starvation-induced hepatic lipotoxicity.

Starvation causes the accumulation of lipid droplets in the liver, a somewhat counterintuitive phenomenon that is nevertheless conserved from flies to humans. Much like fatty liver resulting from overfeeding, hepatic lipid accumulation (steatosis) during undernourishment can lead to lipotoxicity and atrophy of the liver. Here, we found that while surface populations of Astyanax mexicanus undergo this evolutionarily conserved response to starvation, the starvation-resistant cavefish larvae of the same species do not display an accumulation of lipid droplets upon starvation.

HAMSAB diet ameliorates dysfunctional signaling in pancreatic islets in autoimmune diabetes.

An altered gut microbiota is associated with type 1 diabetes (T1D), affecting the production of short-chain fatty acids (SCFA) and glucose homeostasis. We previously demonstrated that enhancing serum acetate and butyrate using a dietary supplement (HAMSAB) improved glycemia in non-obese diabetic (NOD) mice and patients with established T1D. The effects of SCFA on immune-infiltrated islet cells remain to be clarified.

Transplantable human thyroid organoids generated from embryonic stem cells to rescue hypothyroidism.

The thyroid gland captures iodide in order to synthesize hormones that act on almost all tissues and are essential for normal growth and metabolism. Low plasma levels of thyroid hormones lead to hypothyroidism, which is one of the most common disorder in humans and is not always satisfactorily treated by lifelong hormone replacement. Therefore, in addition to the lack of in vitro tractable models to study human thyroid development, differentiation and maturation, functional human thyroid organoids could pave the way to explore new therapeutic approaches.

Loss of tetraspanin-7 expression reduces pancreatic β-cell exocytosis Ca sensitivity but has limited effect on systemic metabolism.

Background: Tetraspanin-7 (Tspan7) is an islet autoantigen involved in autoimmune type 1 diabetes and known to regulate β-cell L-type Ca channel activity. However, the role of Tspan7 in pancreatic β-cell function is not yet fully understood.

Methods: Histological analyses were conducted using immunostaining.

In vivo imaging of calcium dynamics in zebrafish hepatocytes.

Background And Aims: Hepatocytes were the first cell type for which oscillations of cytoplasmic calcium levels in response to hormones were described. Since then, investigation of calcium dynamics in liver explants and culture has greatly increased our understanding of calcium signaling. A bottleneck, however, exists in observing calcium dynamics in a noninvasive manner because of the optical inaccessibility of the mammalian liver.

NF-κB-inducing kinase (NIK) is activated in pancreatic β-cells but does not contribute to the development of diabetes.

The transcription factor nuclear factor-κB (NF-κB) has a key role in the pathogenesis of diabetes and its complications. Although activation of the canonical NF-κB pathway in β-cells is generally deleterious, little is known about the role of the non-canonical NF-κB signalling and its main regulator, the NF-κB-inducing kinase (NIK), on pancreatic β-cell survival and function. Previous studies based on models of NIK overexpression in pancreatic islet cells showed that NIK induced either spontaneous β-cell death due to islet inflammation or glucose intolerance during diet-induced obesity (DIO) in mice.

Keratin filaments mediate the expansion of extra-embryonic membranes in the post-gastrulation mouse embryo.

Mesoderm arises at gastrulation and contributes to both the mouse embryo proper and its extra-embryonic membranes. Two-photon live imaging of embryos bearing a keratin reporter allowed recording filament nucleation and elongation in the extra-embryonic region. Upon separation of amniotic and exocoelomic cavities, keratin 8 formed apical cables co-aligned across multiple cells in the amnion, allantois, and blood islands.

PTPN2 Regulates the Interferon Signaling and Endoplasmic Reticulum Stress Response in Pancreatic β-Cells in Autoimmune Diabetes.

Type 1 diabetes (T1D) results from autoimmune destruction of β-cells in the pancreas. Protein tyrosine phosphatases (PTPs) are candidate genes for T1D and play a key role in autoimmune disease development and β-cell dysfunction. Here, we assessed the global protein and individual PTP profiles in the pancreas from nonobese mice with early-onset diabetes (NOD) mice treated with an anti-CD3 monoclonal antibody and interleukin-1 receptor antagonist.

Single-Cell Trajectory Inference Guided Enhancement of Thyroid Maturation Using TGF-Beta Inhibition.

The thyroid gland regulates metabolism and growth secretion of thyroid hormones by thyroid follicular cells (TFCs). Loss of TFCs, by cellular dysfunction, autoimmune destruction or surgical resection, underlies hypothyroidism. Recovery of thyroid hormone levels by transplantation of mature TFCs derived from stem cells holds great therapeutic promise.

In vivo proximity labeling identifies cardiomyocyte protein networks during zebrafish heart regeneration.

Strategies have not been available until recently to uncover interacting protein networks specific to key cell types, their subcellular compartments, and their major regulators during complex in vivo events. Here, we apply BioID2 proximity labeling to capture protein networks acting within cardiomyocytes during a key model of innate heart regeneration in zebrafish. Transgenic zebrafish expressing a promiscuous BirA2 localized to the entire myocardial cell or membrane compartment were generated, each identifying distinct proteomes in adult cardiomyocytes that became altered during regeneration.

Single-cell transcriptome analysis reveals thyrocyte diversity in the zebrafish thyroid gland.

The thyroid gland regulates growth and metabolism via production of thyroid hormone in follicles composed of thyrocytes. So far, thyrocytes have been assumed to be a homogenous population. To uncover heterogeneity in the thyrocyte population and molecularly characterize the non-thyrocyte cells surrounding the follicle, we developed a single-cell transcriptome atlas of the region containing the zebrafish thyroid gland.

Leader β-cells coordinate Ca dynamics across pancreatic islets in vivo.

Pancreatic β-cells form highly connected networks within isolated islets. Whether this behaviour pertains to the situation in vivo, after innervation and during continuous perfusion with blood, is unclear. In the present study, we used the recombinant Ca sensor GCaMP6 to assess glucose-regulated connectivity in living zebrafish Danio rerio, and in murine or human islets transplanted into the anterior eye chamber.

Nuclei Isolation from Whole Tissue using a Detergent and Enzyme-Free Method.

High-throughput transcriptome and epigenome profiling requires preparation of a single cell or single nuclei suspension. Preparation of the suspension with intact cell or nuclei involves dissociation and permeabilization, steps that can introduce unwanted noise and undesirable damage. Particularly, certain cell-types such as neurons are challenging to dissociate into individual cells.