title: Phenotype of entero-endocrine L cells becomes restricted during development.
abstract: BACKGROUND
  Glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP) are hormones secreted by L and K cells, respectively, and by LK cells. To characterize L and K cells during development, we examined ileum from embryonic (e)- 12 to e-17.
  
  
  RESULTS
  GLP-1 cells were first seen at e-15 and their number increased at e-17. At e-17, most GLP-1 cells co-expressed GIP. The transcription factors Pax6 and Pdx-1 are required for GIP expression, while Pax6 activates the expression of GLP-1. At e-17, the mucosa has GIP+ Pax6+, GIP+ Pdx-1+, GLP-1+ Pax6+, and GLP-1+ Pdx-1+ cells. Unlike ileal L cells of postnatal and adult mice, a subset of ileal L cells of e-17 embryos co-expressed GLP-1 and glucagon (Glu). Glu-positive cells contain proprotein-convertase 2 (PC2) and PC3/1, the enzymes responsible for Glu and GLP-1 synthesis, respectively.
  
  
  CONCLUSIONS
  Our findings indicate that most GLP-1+ cells of ileum of e-17 embryos co-express GIP and, therefore, are LK cells. In addition, a subset of GLP-1+ cells of embryos but not of neonates co-express glucagon, indicating that the expression of Glu in GLP-1+ cells disappears after birth.
authors.affiliation: Department of Cell Biology, SUNY-Downstate Medical Center, Brooklyn, New York 11203, USA.
authors.forename: Marine
authors.initials: M
authors.lastname: Grigoryan
authors.forename: Mamdouh H
authors.initials: MH
authors.lastname: Kedees
authors.forename: Yelena
authors.initials: Y
authors.lastname: Guz
authors.forename: Gladys
authors.initials: G
authors.lastname: Teitelman
mesh_terms: D000818:Animals; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D019858:Enteroendocrine Cells / Q000166:cytology / Q000378:metabolism*; D005749:Gastric Inhibitory Polypeptide / Q000096:biosynthesis* / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D052216:Glucagon-Like Peptide 1 / Q000096:biosynthesis* / Q000235:genetics; D007082:Ileum / Q000166:cytology / Q000196:embryology*; D051379:Mice; D043484:Proprotein Convertases / Q000096:biosynthesis / Q000235:genetics
chemical_list: D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D043484:Proprotein Convertases