title: Retinoic acid plays an evolutionarily conserved and biphasic role in pancreas development.
abstract: As the developing zebrafish pancreas matures, hormone-producing endocrine cells differentiate from pancreatic Notch-responsive cells (PNCs) that reside within the ducts. These new endocrine cells form small clusters known as secondary (2°) islets. We use the formation of 2° islets in the pancreatic tail of the larval zebrafish as a model of β-cell neogenesis. Pharmacological inhibition of Notch signaling leads to precocious endocrine differentiation and the early appearance of 2° islets in the tail of the pancreas. Following a chemical screen, we discovered that blocking the retinoic acid (RA)-signaling pathway also leads to the induction of 2° islets. Conversely, the addition of exogenous RA blocks the differentiation caused by Notch inhibition. In this report we characterize the interaction of these two pathways. We first verified that signaling via both RA and Notch ligands act together to regulate pancreatic progenitor differentiation. We produced a transgenic RA reporter, which demonstrated that PNCs directly respond to RA signaling through the canonical transcriptional pathway. Next, using a genetic lineage tracing approach, we demonstrated these progenitors produce endocrine cells following inhibition of RA signaling. Lastly, inhibition of RA signaling using a cell-type specific inducible cre/lox system revealed that RA signaling acts cell-autonomously in PNCs to regulate their differentiation. Importantly, the action of RA inhibition on endocrine formation is evolutionarily conserved, as shown by the differentiation of human embryonic stem cells in a model of human pancreas development. Together, these results revealed a biphasic function for RA in pancreatogenesis. As previously shown by others, RA initially plays an essential role during embryogenesis as it patterns the endoderm and specifies the pancreatic field. We reveal here that later in development RA is involved in negatively regulating the further differentiation of pancreatic progenitors and expands upon the developmental mechanisms by which this occurs.
authors.affiliation: Department of Surgery, and McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, 733 N. Broadway, 470 Miller Research Building, Baltimore, MD 21205, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.affiliation: Department of Surgery, and McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, 733 N. Broadway, 470 Miller Research Building, Baltimore, MD 21205, USA.
authors.forename: Guangliang
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Surgery, and McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, 733 N. Broadway, 470 Miller Research Building, Baltimore, MD 21205, USA.
authors.forename: Fabien
authors.initials: F
authors.lastname: Delaspre
authors.affiliation: Department of Surgery, and McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, 733 N. Broadway, 470 Miller Research Building, Baltimore, MD 21205, USA.
authors.forename: Maria Del Carmen
authors.initials: Mdel C
authors.lastname: Vitery
authors.affiliation: Department of Surgery, and McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, 733 N. Broadway, 470 Miller Research Building, Baltimore, MD 21205, USA.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Beer
authors.affiliation: Department of Surgery, and McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, 733 N. Broadway, 470 Miller Research Building, Baltimore, MD 21205, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Parsons
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D019070:Cell Lineage; D055098:Endocrine Cells / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D038081:Organogenesis; D010179:Pancreas / Q000196:embryology*; D051880:Receptors, Notch / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D014212:Tretinoin / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins
chemical_list: D051880:Receptors, Notch; D029961:Zebrafish Proteins; D014212:Tretinoin
keywords: Differentiation; Pancreas; Progenitors; Retinoic acid