Embryological origin of interstitial cells of Cajal

Until recently, the embryological origin of the interstitial cells of Cajal (ICC) within the intestine was unclear. An origin from the neural crest or from the mesenchyme was considered possible because ICC possess some chara cteristics in common with neural crest-derived cells, and some characterist ics in common with cells derived from the mesenchyme, Experiments in both m ammalian and avian species, in which segments of embryonic gut were removed prior to the arrival of neural crest cells and grown in organ culture, hav e now shown that ICC do not arise from the neural crest. It appears that IC C and smooth muscle cells arise from common mesenchymal precursor cells. Fr om mid-embryonic stages, ICC precursors express Kit, which is a receptor ty rosine kinase, Both ICC and many smooth muscle cell precursors initially ex press Kit, and then the cells destined to become smooth muscle cells down-r egulate Kit and up-regulate the synthesis of myofilament proteins, whereas cells destined to differentiate into ICC maintain their expression of Kit. Adult mice with mutations that block the activity of Kit have disrupted arr ays of ICC, whereas normal ICC are present until shortly after birth in suc h mice. It, therefore, appears that the Kit signalling pathway in not neces sary for the embryonic development of ICC, but rather the post-natal prolif eration of ICC. (C) 1999 Wiley-Liss, Inc.