Spatial and temporal patterns of c-kit-expressing cells in WlacZ/+ and WlacZ/WlacZ mouse embryos.
In the mouse, the Kit receptor and its ligand, the stem cell factor (SCF), are encoded at the W/Kit and Steel loci, respectively. The Kit/SCF transduction pathway is involved in promoting cellular migration, proliferation and/or survival of melanoblasts, hematopoietic progenitors and primordial germ cells. Furthermore, a functional Kit/SCF pathway is required for the development of interstitial cells of Cajal (ICC) in the small intestine. Whereas all c-kit-expressing cells in embryogenesis were not identified, previous studies clearly demonstrated that the c-kit expression pattern extends well beyond cells known to be affected by W mutations. To investigate further Kit function, we specifically marked the c-kit-expressing cells and followed their fate during embryogenesis. A mutation was introduced by gene targeting at the W/Kit locus in mouse embryonic stem cells. The lacZ reporter gene was inserted into the first exon of c-kit, thus creating a null allele, called WlacZ. The lacZ expression reflects normal expression of the c-kit gene in WlacZ/+ embryos. The comparison of the patterns of lacZ-expressing cells between WlacZ/+ and WlacZ/WlacZ embryos allowed us to detect where and when melanoblasts, primordial germ cells and hematopoietic progenitors failed to survive in the absence of Kit. We also observed that ICC express c-kit during embryogenesis. ICC are found identically in WlacZ/+ and WlacZ/WlacZ embryos. Therefore, ICC do not depend on Kit expression during embryogenesis. These results indicate that the function of the c-kit gene is only required for the postnatal development of the ICC. Unexpected sites of c-kit expression were uncovered in embryos, including endothelial, epithelial and endocrine cells. None of these cells are dependent on Kit expression for their migration, proliferation and/or survival during embryogenesis. Nevertheless, we assume that the Kit/SCF pathway could be involved in the growth of transformed endothelial, epithelial and endocrine cells.
Bernex
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F
URA-INRA de Génétique Moléculaire, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France.
De Sepulveda
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P
Kress
C
C
Elbaz
C
C
Delouis
C
C
Panthier
J J
JJ
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D015870:Gene Expression; D006410:Hematopoiesis; D007763:Lac Operon; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016296:Mutagenesis; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*
D019009:Proto-Oncogene Proteins c-kit