Interstitial cells of Cajal in Wsh/Wsh c-kit mutant mice.

The c-Kit receptor tyrosine kinase regulates the development and differentiation of several progenitor cells. In the gastrointestinal (GI) tract, the c-Kit regulates the development of the interstitial cells of Cajal (ICC) that are responsible for motility regulation of the GI musculature. W-sash (W^sh) is an inversion mutation upstream of the c-kit promoter region that affects a key regulatory element, resulting in cell-type-specific altered gene expression, leading to a decrease in the number of mast cells, melanocytes, and ICC. We extensively examined the GI tract of W^sh/W^sh mice using immunohistochemistry and electron microscopy. Although the musculature of the W^sh/W^sh mice did not show any c-Kit immunoreactivity, we detected intensive immunoreactivity for transmembrane member 16A (TMEM16A, anoctamin-1), another ICC marker. TMEM16A immunopositive cells were observed as ICC-MY in the gastric corpus-antrum and the large intestine, ICC-DMP in the small intestine, and ICC-SM in the colon. Electron microscopic analysis revealed these cells as ICC from their ultrastructural features, such as numerous mitochondria and caveolae, and their close contact with nerve terminals. In the developmental period, we examined 14.5 and 18.5 day embryos but did not observe c-Kit immunoreactivity in the W^sh/W^sh small intestine. From this study, ICC subtypes developed and maturated structurally without c-Kit expression. W^sh/W^sh mice are a new model to investigate the effects of c-Kit and unknown signaling on ICC development and function.