The boundary cap: a source of neural crest stem cells that generate multiple sensory neuron subtypes

The boundary cap (BC) is a transient neural crest-derived group of cells located at the dorsal root entry zone (DREZ) that have been shown to differentiate into sensory neurons and glia in vivo. We find that when placed in culture, BC cells self-renew, show multipotency in clonal cultures and express neural crest stem cell (NCSCs) markers. Unlike sciatic nerve NCSCs, the BC-NCSC (bNCSCs) generates sensory neurons upon differentiation. The bNCSCs constitute a common source of cells for functionally diverse types of neurons, as a single bNCSC can give rise to several types of nociceptive and thermoreceptive sensory neurons. Our data suggests that BC cells comprise a source of multipotent sensory specified stem cells that persist throughout embryogenesis.     

A critical period for conversion of ectodermal cells to a neural crest fate

Previously, we found that interactions between neural and nonneural ectoderm can generate neural crest cells, with both the ectodermal and the neuroepithelial cells contributing to induced population (M. A. J. Selleck and M. Bronner-Fraser, 1995, Development 121, 525-538). To further characterize the ability of ectodermal cells to form neural crest, we have challenged their normal fate by transplanting them into the neural tube. To ensure that the ectoderm was from nonneural regions, we utilized extraembryonic ectoderm (the proamnion) and transplanted it into the presumptive midbrain of 1. 5-day-old chick embryos. We observed that the grafted ectoderm has the capacity to adopt a neural crest fate, responding within a few hours of surgery by turning on neural crest markers HNK-1 and Slug. However, the competence of the ectoderm to respond to neural crest-inducing signals is time limited, declining rapidly in donors older than the 10-somite stage. Similarly, the inductive capacity of the host midbrain declines in a time-dependent fashion. Our results show that extraembryonic ectoderm has the capacity to form neural crest cells given proper inducing signals, expressing both morphological and molecular markers characteristic of neural crest cells.     

Lumbo-sacral neural crest derivatives fate mapped with the aid of Wnt-1 promoter integrate but are not essential to kidney development

Neural crest (NC) cells may be involved in kidney organogenesis by providing inductive signals and contributing to cells of the renal stroma. We show here that the lumbo-sacral NC cells fate mapped with the aid of Wnt-1 promoter in the mouse migrate close to the metanephros at the initiation of organogenesis but these cells remain superficial to the condensed Pax2-expressing mesenchymal cells. NC-derived cells enter later into the kidney proper from the midline region. The NC cells contribute also to development of the extra-adrenal para-aortic bodies, Zuckerkandl's bodies and the nerve cord of the sympathetic nervous system. Splotch (Sp^2H/Sp^2H) embryos, having a NC defect in the lumbo-sacral region, develop a normal metanephros even though the kidney does not express the NC markers Sox10, Phox2b and tyrosine hydroxylase. Consistent with the histological findings, the kidneys of Sp^2H/Sp^2H embryos also express the stromal genes Foxd1, Hoxa10 and RARβ normally. Wnt-1 promoter-marked wild-type LacZ NC cells migrate intensely from the heterologous inducer tissue of the embryonic dorsal spinal cord (SPC) to the kidney mesenchyme, but tubule induction does not depend on NC migration, since the Sp^2H/Sp^2H SPC also induces tubulogenesis. The Sp^2H/Sp^2H mesenchyme also remains competent for tubulogenesis. We conclude that the NC cells fate mapped with the aid of Wnt-1 promoter migrate to the close to the metanephros and form later derivatives integrating with the kidney, but they may not be essential to the development of the stromal cells nor they may provide critical morphogenetic signals to regulate early kidney development in vivo.     

The phenotypic response of cultured quail trunk neural crest cells to a reconstituted basement membrane-like matrix is specific

Previous work has demonstrated that a reconstituted basement membrane (RBM)-like matrix stimulates the development of catecholamine (CA)-containing cells in neural crest cultures. In the present work, we found that the proportion of tyrosine hydroxylase and somatostatin immunoreactive cells was increased substantially by an overlay of the RBM matrix. In contrast, there was little or no stimulation of the development of cells possessing several other phenotypic markers including A2B5, E/C8, vasoactive intestinal polypeptide, and the low and middle molecular weight avian neurofilament proteins. These results demonstrate that the response of neural crest cells to the RBM matrix is specific to a small set of phenotypes. In addition, we demonstrate that the phenotype of the adrenergic cells which develop in the presence of the RBM gel overlay is very similar, if not identical, to that of the adrenergic cells which differentiate in the absence of the RBM gel.     

Distribution of pluripotent neural crest cells in the embryo and the role of brain-derived neurotrophic factor in the commitment to the primary sensory neuron lineage

Many early migratory neural crest cells are pluripotent in the sense that their progeny are able to generate more than one differentiated phenotype (Sieber-Blum and Cohen, 1980, Dev. Biol. 80:95–106; Baroffio, Dupin, and Le Douarin, 1988, Proc. Natl. Acad. Sci. USA 85:5325–5329; Bronner-Fraser and Fraser, 1988, Nature 335:161–164; Sieber-Blum, 1989a, Science 243:1608–1611; Ito and Sieber-Blum, 1991, Dev. Biol. 148:95–106). At trunk levels, the neural crest contains two classes (Sieber-Blum and Cohen, 1980) and at posterior rhombencephalic levels, three different classes of pluripotent cells (Ito and Sieber-Blum, 1991). We investigated cell differentiation by in vitro clonal analysis to determine when in development the pool of pluripotent neural crest cells becomes exhausted. The data suggest that different classes of pluripotent cells, precursor cells with more restricted developmental potentials, and apparently committed cells, exist at sites of advanced migration (posterior branchial arches) and even at target sites of neural crest cell differentiation [posterior branchial arches, dorsal root ganglia (DRG), sympathetic ganglia (SG), and epidermal ectoderm]. Some putative classes of pluripotent cells persist well into the second half of embryonic development. These observations have implications for our understanding of the mechanisms that control neural crest cell migration and differentiation. They support the idea that cues originating from the microenvironment affect differentiation of pluripotent neural crest cells. One such signal appears to be brain-derived neurotrophic factor (BDNF). In the presence of BDNF, but not nerve growth factor (NGF), there is a significant increase in the number of neural crest cells per colony that express a sensory neuron-specific marker. Because this increase is not accompanied by a corresponding increase in the total number of cells per colony, this suggests that BDNF plays a role in cell type specification. © 1993 John Wiley & Sons, Inc.