Neurotrophin-3 (NT-3), which is essential for the survival of a large proportion of vagal sensory neurons, is expressed in the developing gastrointestinal (GI) tract where it could contribute to this survival, to other aspects of vagal afferent development, and to the development of spinal afferents, postganglionic sympathetic neurons and intrinsic neurons. Identifying the functions of this peripheral NT-3 requires a detailed understanding of the localization and timing of its expression in the developing GI tract. Therefore, X-gal staining of embryos and neonates expressing the lacZ reporter gene from the NT-3 locus was used to characterize the spatiotemporal pattern of NT-3 expression during development. NT-3 expression in the stomach, and intestines was largely restricted to smooth muscle of the outer GI wall and associated blood vessels. However, expression also occurred in the stomach lamina propria and esophageal epithelium. NT-3 expression occurred in GI wall mesenchyme by embryonic day (E)12.5 and became restricted to smooth muscle and lamina propria by E15.5 as these tissues differentiated, whereas expression in blood vessels and esophageal epithelium was first observed at E15.5. Immunohistochemical detection of b-galactosidase and cell type markers suggested myenteric elements, including neurons, glial cells, neural and glial precursors, and interstitial cells of Cajal did not express NT-3. Thus, NT-3 expression in the GI tract was largely restricted to smooth muscle at ages when vagal axons grow into the GI tract and vagal mechanoreceptors form in smooth muscle, consistent with roles in these processes, in vagal sensory neuron survival, and in development of intrinsic and other extrinsic GI wall innervation.


Originally posted and published through Cell and Tissue Research through Springer and can be found at the following link: http://www.ncbi.nlm.nih.gov/pubmed/20387078. The final publication is available at link.springer.com

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