On the diabetic menu: Zebrafish as a model for pancreas development and function (original) (raw)
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Zebrafish pancreas development
Molecular and Cellular Endocrinology, 2009
An accurate understanding of the molecular events governing pancreas development can have an impact on clinical medicine related to diabetes, obesity and pancreatic cancer, diseases with a high impact in public health. Until 1996, the main animal models in which pancreas formation and differentiation could be studied were mouse and, for some instances related to early development, chicken and Xenopus. Zebrafish has penetrated this field very rapidly offering a new model of investigation; by joining functional genomics, genetics and in vivo whole mount visualization, Danio rerio has allowed large scale and fine multidimensional analysis of gene functions during pancreas formation and differentiation.
Retinoic Acid Signaling Is Required for a Critical Early Step in Zebrafish Pancreatic Development
Current Biology, 2002
derm patterning. BMS493-treated embryos appeared healthy and, similar to nls mutants [4], lacked pectoral fin buds and exhibited a reduction in the anteroposterior (AP) extent of the hindbrain (data not shown). Genetics and Evolutionary Biology ment of developmental control genes and hormones as the mammalian pancreas [12] . In BMS493-The University of Chicago 1027 East 57 th Street treated embryos, expression of endocrine genes (insulin, somatostatin, and glucagon; markers of differenti-Chicago, Illinois 60637 ated , ␦, and ␣ cells, respectively [12-14]), and trypsin (an exocrine cell marker [14]), was undetectable from the onset of normal expression through 72 hpf (hours Summary post fertilization; the mean stage to which treated embryos survived) (Figures 1A- ). We were The mechanisms that subdivide the endoderm into the similarly unable to detect any endocrine marker expresdiscrete primordia that give rise to organs such as the sion in the vast majority of nls embryos (Figures 1O pancreas and liver are not well understood. However, and 1P), and expression of trypsin was either absent or it is known that retinoic acid (RA) signaling is critical greatly reduced ( ). As treatment with for regionalization of the vertebrate embryo: when RA BMS493 is known to completely abrogate all RA signalsignaling is either prevented or augmented, anteroing, we conclude that RA is necessary for differentiation
Analysis of pancreatic development in living transgenic zebrafish embryos
Molecular and Cellular Endocrinology, 2001
Using DNA constructs containing regulatory sequences of the zebrafish Pdx-1 and insulin genes, germline transgenic zebrafish expressing the green fluorescent protein (GFP) reporter gene in the pancreas were generated. For both constructs, the GFP expression patterns in transgenic embryos were consistent with the mRNA expression patterns detected by RNA in situ hybridization. A deletion promoter analysis revealed that positive and negative cis-acting elements were involved in regulation of insulin gene expression. Three-dimensional reconstructions imaged from living embryos using two-photon laser-scanning microscopy (TPLSM) demonstrated that the zebrafish pancreas is formed from a single dorsal pancreatic cell mass. This is in contrast to mammals where the pancreas derives from both dorsal and ventral anlage. These transgenic fish should be useful for in vivo studies of factors involved in specifying and regulating pancreatic development and function.
Regeneration of the Pancreas in Adult Zebrafish
Diabetes, 2009
OBJECTIVE-Regenerating organs in diverse biological systems have provided clues to processes that can be harnessed to repair damaged tissue. Adult mammalian -cells have a limited capacity to regenerate, resulting in diabetes and lifelong reliance on insulin. Zebrafish have been used as a model for the regeneration of many organs. We demonstrate the regeneration of adult zebrafish pancreatic -cells. This nonmammalian model can be used to define pathways for islet-cell regeneration in humans. RESEARCH DESIGN AND METHODS-Adult transgenic zebrafish were injected with a single high dose of streptozotocin or metronidazole and anesthetized at 3, 7, or 14 days or pancreatectomized. Blood glucose measurements were determined and gut sections were analyzed using specific endocrine, exocrine, and duct cell markers as well as markers for dividing cells. RESULTS-Zebrafish recovered rapidly without the need for insulin injections, and normoglycemia was attained within 2 weeks. Although few proliferating cells were present in vehicles, ablation caused islet destruction and a striking increase of proliferating cells, some of which were Pdx1 positive. Dividing cells were primarily associated with affected islets and ducts but, with the exception of surgical partial pancreatectomy, were not extensively -cells. CONCLUSIONS-The ability of the zebrafish to regenerate a functional pancreas using chemical, genetic, and surgical approaches enabled us to identify patterns of cell proliferation in islets and ducts. Further study of the origin and contribution of proliferating cells in reestablishing islet function could provide strategies for treating human diseases.
Hedgehog signaling pathway is essential for pancreas specification in the zebrafish embryo
Current Biology, 2001
expression in the presumptive dorsal and ventral pancreatic buds appears to be critical for committing these re-Sonic hedgehog (Shh) as a negative regulator of pancreatic development, but as a positive regulator gions to a pancreatic fate; in the dorsal primordium at least, this repression seems to be mediated by notochordof pancreas function in amniotes [1-4]. Here, using genetic analysis, we show that specification of the derived signals such as activins and fibroblast growth factors (FGFs) [6-8]. Moreover, alterations in the levels of pancreas in the teleost embryo requires the activity of Hh proteins. Zebrafish embryos compromised in Hh signaling in these organisms are associated with developmental changes in the pancreas that are consistent with Hh signaling exhibit disruption in the expression of the pancreas-specifying homeobox gene pdx-1 the idea that Hh negatively regulates pancreas specification [9-11]. and concomitantly show almost complete absence of the endocrine pancreas. Reciprocally, ubiquitous activation of the Hh pathway in wild-type embryos The homeobox gene Pdx-1 plays a central role in pancreas causes ectopic induction of endodermal pdx-1 development in amniotes [12-15]. Its spatially restricted expression and the differentiation of expression in the developing gut is one of the earliest supernumerary endocrine cells. Our results suggest markers of the presumptive pancreatic primordia and is that Hh proteins influence pancreas specification critically dependent on the exclusion of Shh expression via inductive interactions from the axial midline from these endodermal cells [6, 14, 16, 17]. In wild-type rather than through their localized expression in zebrafish embryos, pdx-1 expression is observed as early the endodermal cells themselves. as the 10 to 12 somite stage in a localized bilateral patch of anterior-gut endodermal cells overlying the yolk mass (24 hr postfertilization [hpf]), this early bilateral patch 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom. of pdx-1 expression has resolved into a discrete domain comprising a dorsal component of high-level expression of zebrafish pdx-1 [18-21], we wondered whether it is developmentally regulated by similar kinds of inductive
Generation of a Transgenic Zebrafish Model for Pancreatic Beta Cell Regeneration
Galen Medical Journal, 2019
Background: Diabetes is a major worldwide health problem. It is widely accepted that the beta cell mass decreases in type I diabetes (T1D). Accordingly, beta cell regeneration is a promising approach to increase the beta cell mass in T1D patients. However, the underlying mechanisms of beta cell regeneration have yet to be elucidated. One promising avenue is to create a relevant animal model to explore the underlying molecular and cellular mechanisms of beta cell regeneration. The zebrafish can be considered a model in beta cell regeneration studies because the pancreas structure and gene expression pattern are highly conserved between human and zebrafish. Materials and Methods: In this study, the Tol2 transposase was exploited to generate a Tg(Ins:egfp-nfsB) zebrafish model that expressed a fusion protein composed of enhanced green fluorescent protein (EGFP) and nitroreductase (NTR) under control of the Ins promoter. Results: Metronidazole (MTZ) treatment of Tg(ins:egfp-nfsB) zebraf...
The Notch-signaling pathway is known to be fundamental in controlling pancreas differentiation. We now report on using Crebased fate mapping to indelibly label pancreatic Notch-responsive cells (PNCs) at larval stages and follow their fate in the adult pancreas. We show that the PNCs represent a population of progenitors that can differentiate to multiple lineages, including adult ductal cells, centroacinar cells (CACs) and endocrine cells. These endocrine cells include the insulin-producing -cells. CACs are a functional component of the exocrine pancreas; however, our fate-mapping results indicate that CACs are more closely related to endocrine cells by lineage as they share a common progenitor. The majority of the exocrine pancreas consists of the secretory acinar cells; however, we only detect a very limited contribution of PNCs to acinar cells. To explain this observation we re-examined early events in pancreas formation. The pancreatic anlage that gives rise to the exocrine pancreas is located in the ventral gut endoderm (called the ventral bud). Ptf1a is a gene required for exocrine pancreas development and is first expressed as the ventral bud forms. We used transgenic marker lines to observe both the domain of cells expressing ptf1a and cells responding to Notch signaling. We do not detect any overlap in expression and demonstrate that the ventral bud consists of two cell populations: a ptf1-expressing domain and a Notch-responsive progenitor core. As pancreas organogenesis continues, the ventral bud derived PNCs align along the duct, remain multipotent and later in development differentiate to form secondary islets, ducts and CACs.
Developmental Biology, 2001
To begin to understand pancreas development and the control of endocrine lineage formation in zebrafish, we have examined the expression pattern of several genes shown to act in vertebrate pancreatic development: pdx-1, insulin (W. M. ). To determine the spatial relationship between the exocrine and the endocrine compartments, we have cloned the zebrafish trypsin gene, a digestive enzyme expressed in differentiated pancreatic exocrine cells. We found expression of all these genes in the developing pancreas throughout organogenesis. Endocrine cells first appear in a scattered fashion in two bilateral rows close to the midline during mid-somitogenesis and converge during late-somitogenesis to form a single islet dorsal to the nascent duodenum. We have examined development of the endocrine lineage in a number of previously described zebrafish mutations. Deletion of chordamesoderm in floating head (Xnot homolog) mutants reduces islet formation to small remnants, but does not delete the pancreas, indicating that notochord is involved in proper pancreas development, but not required for differentiation of pancreatic cell fates. In the absence of knypek gene function, which is involved in convergence movements, the bilateral endocrine primordia do not merge. Presence of trunk paraxial mesoderm also appears to be instrumental for convergence since the bilateral endocrine primordia do not merge in spadetail mutants. We discuss our findings on zebrafish pancreatogenesis in the light of evolution of the pancreas in chordates.
Exocrine pancreas development in zebrafish
Developmental Biology, 2005
Although many of the genes that regulate development of the endocrine pancreas have been identified, comparatively little is known about how the exocrine pancreas forms. Previous studies have shown that exocrine pancreas development may be modeled in zebrafish. However, the timing and mechanism of acinar and ductal differentiation and morphogenesis have not been described. Here, we characterize zebrafish exocrine pancreas development in wild type and mutant larvae using histological, immunohistochemical and ultrastructural analyses. These data allow us to identify two stages of zebrafish exocrine development. During the first stage, the exocrine anlage forms from rostral endodermal cells. During the second stage, protodifferentiated progenitor cells undergo terminal differentiation followed by acinar gland and duct morphogenesis. Immunohistochemical analyses support a model in which the intrapancreatic ductal system develops from progenitors that join to form a contiguous network rather than by branching morphogenesis of the pancreatic epithelium, as described for mammals. Contemporaneous appearance of acinar glands and ducts in developing larvae and their disruption in pancreatic mutants suggest that common molecular pathways may regulate gland and duct morphogenesis and differentiation of their constituent cells. By contrast, analyses of mind bomb mutants and jagged morpholino-injected larvae suggest that Notch signaling principally regulates ductal differentiation of bipotential exocrine progenitors. D