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The cochleovestibular (CV) nerve, which connects the inner ear to the brain, is the nerve that enables the senses of hearing and balance. The aim of this study was to document the morphological development of the mouse CV nerve with respect to the two embryonic cells types that produce it, specifically, the otic vesicle-derived progenitors that give rise to neurons, and the neural crest cell (NCC) progenitors that give rise to glia. Otic tissues of mouse embryos carrying NCC lineage reporter transgenes were whole mount immunostained to identify neurons and NCC. Serial optical sections were collected by confocal microscopy and were compiled to render the three dimensional (3D) structure of the developing CV nerve. Spatial organization of the NCC and developing neurons suggest that neuronal and glial populations of the CV nerve develop in tandem from early stages of nerve formation. NCC form a sheath surrounding the CV ganglia and central axons. NCC are also closely associated with neurites projecting peripherally during formation of the vestibular and cochlear nerves. Physical ablation of NCC in chick embryos demonstrates that survival or regeneration of even a few individual NCC from ectopic positions in the hindbrain results in central projection of axons precisely following ectopic pathways made by regenerating NCC., (© 2013 Published by Elsevier Inc.)

The enteric nervous system (ENS) comprises a complex neuronal network that regulates peristalsis of the gut wall and secretions into the lumen. The ENS is formed from a multipotent progenitor cell population called the neural crest, which is derived from the neuroepithelium. Neural crest cells (NCCs) migrate over incredible distances to colonize the entire length of the gut and during their migration they must survive, proliferate and ultimately differentiate. The absence of an ENS from variable lengths of the colon results in Hirschsprung's disease (HSCR) or colonic aganglionosis. Mutations in about 12 different genes have been identified in HSCR patients but the complex pattern of inheritance and variable penetrance suggests that additional genes or modifiers must be involved in the etiology and pathogenesis of this disease. We discovered that Tcof1 haploinsufficiency in mice models many of the early features of HSCR. Neuroepithelial apoptosis diminished the size of the neural stem cell pool resulting in reduced NCC numbers and their delayed migration along the gut from E10.5 to E14.5. Surprisingly however, we observe continued and complete colonization of the entire colon throughout E14.5-E18.5, a period in which the gut is considered to be non- or less-permissive to NCC. Thus, we reveal for the first time that reduced NCC progenitor numbers and delayed migration do not unequivocally equate with a predisposition for the pathogenesis of HSCR. In fact, these deficiencies can be overcome by balancing NCC intrinsic processes of proliferation and differentiation with extrinsic influences of the gut microenvironment.

The enteric nervous system (ENS) is mainly derived from vagal neural crest cells (NCC) that arise at the level of somites 1-7. To understand how the size and composition of the NCC progenitor pool affects ENS development, we reduced the number of NCC by ablating the neural tube adjacent to somites 3-6 to produce aganglionic gut. We then back-transplanted various somite lengths of quail neural tube into the ablated region to determine the 'tipping point', whereby sufficient progenitors were available for complete ENS formation. The addition of one somite length of either vagal, sacral or trunk neural tube into embryos that had the neural tube ablated adjacent to somites 3-6, resulted in ENS formation along the entire gut. Although these additional cells contributed to the progenitor pool, the quail NCC from different axial levels retained their intrinsic identities with respect to their ability to form the ENS; vagal NCC formed most of the ENS, sacral NCC contributed a limited number of ENS cells, and trunk NCC did not contribute to the ENS. As one somite length of vagal NCC was found to comprise almost the entire ENS, we ablated all of the vagal neural crest and back-transplanted one somite length of vagal neural tube from the level of somite 1 or somite 3 into the vagal region at the position of somite 3. NCC from somite 3 formed the ENS along the entire gut, whereas NCC from somite 1 did not. Intrinsic differences, such as an increased capacity for proliferation, as demonstrated in vitro and in vivo, appear to underlie the ability of somite 3 NCC to form the entire ENS.

The formation of neural tissue, in association with airway smooth muscle (ASM), is a feature of normal lung development and function. Intrinsic neuronal tissue has recently been shown, in animal models, to be derived from neural crest cells (NCC). Since defects in NCC development underlie a range of disease states (neurocristopathies), it is important to determine the spatiotemporal development of NCC in the human lung, as defects in their development could have pathophysiologic implications. The aims of this study were to: (1) establish a time course for the formation of ASM and neural tissue within the embryonic and fetal human lung, (2) investigate whether intrinsic neural tissue within the lung is derived from NCC, and (3) gain insight into the possible signaling mechanisms underlying the development of the intrinsic lung innervation. Using human lung tissue from Weeks 6 to 12 of gestation, we analyzed the formation of ASM, NCC, neuronal and glial tissue, and the expression of Gfralpha1, a receptor component of the RET (rearranged during transfection) tyrosine kinase signaling pathway. Our results showed that NCC accumulated along the branching airways, in close association with the ASM, and differentiated into neurons and glia. Neural crest-derived neural tissue within the lung strongly expressed membrane-bound Gfralpha1, and soluble Gfralpha1 was expressed within the lung mesenchyme, but only at early developmental stages. Together these findings indicate that the intrinsic innervation of the human lung is derived from the neural crest.

The enteric nervous system (ENS) is formed from vagal and sacral neural crest cells (NCC). Vagal NCC give rise to most of the ENS along the entire gut, whereas the contribution of sacral NCC is mainly limited to the hindgut. This, and data from heterotopic quail-chick grafting studies, suggests that vagal and sacral NCC have intrinsic differences in their ability to colonize the gut, and/or to respond to signalling cues within the gut environment. To better understand the molecular basis of these differences, we studied the expression of genes known to be essential for ENS formation, in sacral NCC within the chick hindgut. Our results demonstrate that, as in vagal NCC, Sox10, EdnrB, and Ret are expressed in sacral NCC within the gut. Since we did not detect a qualitative difference in expression of these ENS genes we performed DNA microarray analysis of vagal and sacral NCC. Of 11 key ENS genes examined from the total data set, Ret was the only gene identified as being highly differentially expressed, with a fourfold increase in expression in vagal versus sacral NCC. We also found that over-expression of RET in sacral NCC increased their ENS developmental potential such that larger numbers of cells entered the gut earlier in development, thus promoting the fate of sacral NCC towards that of vagal NCC.

Background/aims: Hepatic stellate cells (HSC) have been hypothesised to derive from the neural crest, based on their expression of multiple neural/neuroendocrine features and their contacts with autonomic nerve endings., Methods: We studied the emergence of HSC in the liver during embryonic development in a transgenic mouse line expressing yellow fluorescent protein (YFP) in all neural crest cells and their derivatives. Cellular YFP expression in these mice was compared with desmin expression between embryonic day (E) 11.5 and adulthood., Results: YFP was abundantly expressed in neural crest cells delaminating from the neural tube and in all known neural crest-derived structures and cell populations. In particular, YFP expressing cells perfectly mimicked the spatial and temporal pattern of enteric nervous system development from neural crest cells migrating from the postotic region. Cells within the adrenal medulla were also YFP positive. Analysis of the liver showed that desmin-expressing, stellate-shaped, perisinusoidally located HSC were evident from E11.5 onwards. However, no detectable YFP expression was seen in the developing liver or in HSC, from E11.5 until adulthood., Conclusions: These findings suggest HSC do not descend from the neural crest, and therefore may derive from the septum transversum mesenchyme, from endoderm or from the mesothelial liver capsule.