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The structural relationships between interstitial cells of Cajal (ICC), varicose nerve fibers, and smooth muscle cells in the gastrointestinal tract have led to the suggestion that ICC may be involved in or mediate enteric neurotransmission. We characterized the distribution of ICC in the murine stomach and found two distinct classes on the basis of morphology and immunoreactivity to antibodies against c-Kit receptors. ICC with multiple processes formed a network in the myenteric plexus region from corpus to pylorus. Spindle-shaped ICC were found within the circular and longitudinal muscle layers (IC-IM) throughout the stomach. The density of these cells was greatest in the proximal stomach. IC-IM ran along nerve fibers and were closely associated with nerve terminals and adjacent smooth muscle cells. IC-IM failed to develop in mice with mutations in c-kit. Therefore, we used W/WV mutants to test whether IC-IM mediate neural inputs in muscles of the gastric fundus. The distribution of inhibitory nerves in the stomachs of c-kit mutants was normal, but NO-dependent inhibitory neuroregulation was greatly reduced. Smooth muscle tissues of W/Wv mutants relaxed in response to exogenous sodium nitroprusside, but the membrane potential effects of sodium nitroprusside were attenuated. These data suggest that IC-IM play a critical serial role in NO-dependent neurotransmission: the cellular mechanism(s) responsible for transducing NO into electrical responses may be expressed in IC-IM. Loss of these cells causes loss of electrical responsiveness and greatly reduces responses to nitrergic nerve stimulation.Ramon y Cajal observed cells at the terminus of the autonomic nervous system in the acini of salivary glands, in the connective tissue of the pancreas, between the glands of Lieberkuhn, in the intestinal villi, and within the tunica muscularis of the gastrointestinal (GI) tract (1). The processes of cells in the GI tract, which became known as interstitial cells of Cajal (ICC), form a network that is intercalated between nerve terminals and effector cells. Cajal believed that the structures he identified were essential elements in peripheral neurotransmission (2), and this hypothesis has been investigated for the past century (3). ICC were later recognized to be nonneural (4), but their anatomical locations in the GI tract continue to suggest a role for these cells in neurotransmission (3,5 Recently, it was shown that mutations in c-kit, a protooncogene located at the W locus on chromosome 5 in the mouse that encodes a receptor tyrosine kinase (10), or in stem cell factor, the natural ligand for c-Kit receptors, result in developmental defects in some classes of . For example, ICC in the myenteric plexus region (IC-MY) of the small intestine are greatly decreased in numbers in these mutants and slow waves are abolished, confirming a role for IC-MY as pacemakers (3,15,16). ICC in the region of the deep muscular plexus, however, were unaffected by defects in the c-Kit signaling pathway (14). Loss of IC-MY did not af...

3MC syndrome has been proposed as a unifying term to integrate the overlapping Carnevale, Mingarelli, Malpuech and Michels syndromes. These rare autosomal recessive disorders of unknown cause comprise a spectrum of developmental features including characteristic facial dysmorphism, cleft lip and/or palate, craniosynostosis, learning disability, and genital, limb and vesicorenal anomalies. In a cohort of eleven 3MC families, we identified two mutated genes COLEC11 and MASP1 both of which encode proteins within the lectin complement pathway (CL-K1 and MASP-1 & −3 respectively). CL-K1 is highly expressed in embryonic murine craniofacial cartilage, heart, bronchi, kidney, and vertebral bodies. Zebrafish morphants develop pigment defects and severe craniofacial abnormalities.Here, we show that CL-K1 serves as a key guidance cue for neural crest cell migration thus demonstrating for the first time, a role for complement pathway factors in fundamental developmental processes and the origin of 3MC syndrome.

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Electrical rhythmicity in the gastrointestinal tract may originate in interstitial cells of Cajal (IC). Development of IC in the small intestine is linked to signaling via the tyrosine kinase receptor, c-kit. IC express c-kit protein, and disruption of c-kit signaling causes breakdown in IC networks and loss of slow waves. We tested whether mutations in steel factor, the ligand for c-kit, affect the development of IC networks. IC were found in the region of the myenteric plexus (IC-MY) in mice with steel mutations (i.e., Sl/Sld) at 5-10 days postpartum, but these cells formed an abnormal network. IC-MY were not observed in adult Sl/Sld animals. IC in the deep muscular plexus (IC-DMP) appeared normal in Sl/Sld animals. Electrical slow waves, normally present in the small intestine, were absent in Sl/Sld animals (10-30 days postpartum). Neural inputs were intact in Sl/Sld animals. Steel factor appears important for the development of certain classes of IC, and IC-MY appear to be involved in the generation of electrical rhythmicity in the small intestine.