Expression of the Receptor Tyrosine Kinase KIT in Mature β-Cells and in the Pancreas in Development
- Latif Rachdi1,
- Lynda El Ghazi1,
- Florence Bernex2,
- Jean-Jacques Panthier2,
- Paul Czernichow1 and
- Raphael Scharfmann1
- 1Institut National de la Santé et de la Recherche Médicale (INSERM) U457, Hospital R. Debré, Paris
- 2URA-INRA de Génétique Moléculaire, Maisons-Alfort, France
In the pancreas, ligands of receptor tyrosine kinases (RTKs) are thought to be implicated in the development and function of the islets of Langerhans, which represent the endocrine part of the pancreas. In a previous study, we randomly screened by reverse transcriptase−polymerase chain reaction for RTKs expressed in the embryonic pancreas. One cDNA fragment that was cloned during this screen corresponded to the KIT receptor. The objective of the present study was to analyze the pattern of Kit expression in the pancreas. We demonstrated that Kit is expressed and functional in terms of signal transduction in the insulin-producing cell line INS-1. Indeed, upon treatment with the KIT ligand (KITL), the extracellular signal-regulated protein kinase was phosphorylated, and the expression of early responsive genes was induced. We also demonstrated that Kit mRNAs are present in fetal and adult rat islets. We next used mice that had integrated the lacZ reporter gene into the Kit locus. In these mice, β-galactosidase (β-gal) served as a convenient marker for expression of the endogenous Kit gene. Kit was found to be specifically transcribed in β-cells (insulin-expressing cells), whereas no expression was found in other endocrine cell types or in the exocrine tissue. Interestingly, not all mature β-cells expressed Kit, indicating that Kit is a marker of a subpopulation of β-cells. Finally, by following β-gal expression in the pancreas during fetal life, we found that at E14.5, Kit is expressed in both insulin- and glucagon-expressing cells present at that stage, and also in a specific cell population present in the epithelium that stained negative for endocrine markers. These data suggest that these Kit-positive/endocrine-negative cells could represent a subpopulation of endocrine cell precursors.
Address correspondence and reprint requests to Raphael Scharfmann, PhD, INSERM U457, Hospital R. Debré, 48 Blvd. Sérurier, 75019 Paris, France. E-mail:.
Received for publication 31 October 2000 and accepted in revised form 5 June 2001.
BSA, bovine serum albumin; ERK, extracellular signal-regulated protein kinase; β-gal, β-galactosidase; KITL, KIT ligand; MAP, mitogen-activated protein; PBS, phosphate-buffered saline; PBST, PBS containing 0.5% Tween-20; PCR, polymerase chain reaction; PI, phosphatidylinositol; RT, reverse transcriptase; RTK, receptor tyrosine kinase.