Insulin-like genes in ascidians: findings in Ciona and hypotheses on the evolutionary origins of the pancreas.
Insulin plays an extensively characterized role in the control of sugar metabolism, growth and homeostasis in a wide range of organisms. In vertebrate chordates, insulin is mainly produced by the beta cells of the endocrine pancreas, while in non-chordate animals insulin-producing cells are mainly found in the nervous system and/or scattered along the digestive tract. However, recent studies have indicated the notochord, the defining feature of the chordate phylum, as an additional site of expression of insulin-like peptides. Here we show that two of the three insulin-like genes identified in Ciona intestinalis, an invertebrate chordate with a dual life cycle, are first expressed in the developing notochord during embryogenesis and transition to distinct areas of the adult digestive tract after metamorphosis. In addition, we present data suggesting that the transcription factor Ciona Brachyury is involved in the control of notochord expression of at least one of these genes, Ciona insulin-like 2. Finally, we review the information currently available on insulin-producing cells in ascidians and on pancreas-related transcription factors that might control their expression.
Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, New York, New York.
Jordan M
JM
Thompson
Anna
A
Di Gregorio
D000818:Animals; D002938:Ciona intestinalis / Q000196:embryology / Q000235:genetics*; D017124:Conserved Sequence; D019143:Evolution, Molecular; D005326:Fetal Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005819:Genetic Markers; D050417:Insulin-Secreting Cells / Q000166:cytology; D061385:Insulins / Q000737:chemistry / Q000235:genetics*; D008675:Metamorphosis, Biological; D010179:Pancreas / Q000196:embryology*; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000098908:Brachyury Protein
D005326:Fetal Proteins; D005819:Genetic Markers; D061385:Insulins; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D000098908:Brachyury Protein
Brachyury; Ciona; ascidian; cis-regulatory module; insulin; notochord; pancreas; transcription factor