No description available.

No description available.

Next, the influences on the migration of neural crest cell from the microenvironment of the hindgut through which the neural crest cells migrate were studied. An organ culture system was established to recombine different gut segments together at E11.5 for gut culture in order to trace the migration of neural crest cells from the midgut of the +/+ or Dom/+ embryo to the hindgut of the same or different genotypes. At E11.5, the midgut of both +/+ and Dom/+ embryos had already been fully colonized by neural crest cells, thus an explanted midgut segment (donor midgut) could serve as the source of the neural crest cells, while the caudal half of the hindgut (recipient hindgut) acted as the recipient of the neural crest cells from the donor midgut segment because at this stage, the caudal half of the hindgut was completely devoid of neural crest cells. After three days of culture, when a segment of midgut from the +/+ embryo was used as the donor of migratory vagal neural crest-derived cells and combined with an aneural segment of the hindgut (segment without neural crest-derived cells) from Dom/+ or Dom/Dom embryos, neural crest-derived cells from the midgut segment successfully crossed the combination junction and migrated normally along the hindgut segment to reach its caudal end within a normal developmental time frame. However, the migration of neural crest-derived donor cells from the Dom/+ midgut segment was abnormal in the recipient hindgut with a genotype of +/+, Dom/+ or Dom/Dom as evidenced by the retarded rostrocaudal progression of the vagal neural crest-derived cells and the reduced number of migratory cells in the recipient hindgut segment. These results thus indicate that the migration of the vagal neural crest-derived cells is minimally influenced by the migratory environment of the hindgut of the Dom embryo, and that the neural crest cells themselves may be defective in migration leading to the retarded migration in the hindgut of Dom mouse embryos. / The vagal neural crest cells originating from the region of the neural tube adjacent to somites 1 to 7 migrate along defined pathways to the gastrointestinal tract and then colonize the gut to give rise to the majority of neurons and glia of the enteric nervous system. Mutation of Sox10 in the Dominant megacolon (Dom) mouse, which is an animal model of Hirschsprung's disease, leads to aganglionosis (absence of ganglia) in varying lengths of the hindgut. To investigate the underlying cellular mechanism of aganglionosis, the migration of vagal neural crest cells from the neural tube to the gut (pre-enteric migration) in Dom mouse embryos at E8.5 was firstly traced with extrinsic cell markers, such as wheat germ agglutinin gold conjugates (WGA-Au) or fluorescent dye DiI. After the vagal neural crest cells entered the gut at E9.5, their migration was then followed by the examination of the expression of specific markers for undifferentiated neural crest cells with immunohistochemical staining. It was found that, although vagal neural crest cells in embryos of the three genotypes examined migrated along similar pre-enteric pathways at a similar migratory rate, the numbers of neural crest cells in embryos heterozygous (Dom/+) and homozygous (Dom/Dom) for the Sox10 mutation were significantly reduced when compared with the number of neural crest cells in wild-type (+/+) embryos. After vagal neural crest had entered the gut and from E10.5 onwards, no neural crest-derived cells were found in the gut of Dom/Dom embryos, and the migration of neural crest cells along the Dom/+ gut was significantly retarded from E12.5 onwards as compared with the migration in stage-matched +/+ embryos. / To further trace the cause of defective migration of neural crest cells in the Dom embryo, the proliferation and survival of neural crest cells were investigated with BrdU labeling and TUNEL assay. It was found that, although there was no obvious difference in the proliferating ability of vagal neural crest cells in embryos of all the three Dom genotypes studied during the pre-enteric migration and the migration in the gut, more apoptotic neural crest cells were found along the pre-enteric migratory pathway of Dom/Dom embryos than Dom/+ and +/+ embryos. Therefore, the decreased surviving ability, but possibly not the reduced proliferating ability, of neural crest cells during their pre-enteric migration may be partly responsible for aganglionosis in the hindgut of the Dom mouse. / Wang Liang. / "June 2006." / Adviser: W. Y. Chan. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1380. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 287-307). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 160-188).

Thesis (Ph. D.)-- University of Washington, 2005. / Includes bibliographical references (leaves 107-127).

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Neural crest cells (NCC) are a multipotent population of cells that form at the dorsal region of neural tube, migrate and contribute to a vast array of embryonic structures, including the majority of the head, the septum of the cardiac outflow tract (OFT), smooth muscle subpopulations, sympathetic nervous system and many other organs. Anomalous NCC morphogenesis is responsible for a wide variety of congenital defects. Importantly, several individual members of the TGFβ superfamily have been shown to play essential roles in various aspects of normal NCC development. However, it remains unclear what role Smad7, a negative regulator of TGFβ superfamily signaling, plays during development and moreover what the spatiotemporal effects are of combined suppression of TGFβ superfamily signaling during NCC formation and colonization of the developing embryo. Using a cre/loxP three-component triple transgenic system, expression of Smad7 was induced via doxycycline in the majority of pre- and post-migratory NCC lineages (via Wnt1-Cre mice). Further, expression of Smad7 was induced via doxycycline in a subset of post-migratory NCC lineages (via Periostin-Cre mice, after the NCC had reached their target organs and undergone differentiation). Induction of Smad7 within NCC significantly suppressed TGFβ superfamily signaling, as revealed via diminished phosphorylation levels of both Smad1/5/8 and Smad2/3 in vivo. This resulted in subsequent loss of NCC-derived craniofacial, pharyngeal and cardiac OFT cushion tissues. ROSA26r NCC lineage mapping demonstrated that cardiac NCC emigration and initial migration were unaffected, but subsequent colonization of the OFT was significantly reduced. At the cellular level, increased cell death was observed, but cell proliferation and NCC-derived smooth muscle differentiation were unaltered. Molecular analysis demonstrated that Smad7 induction resulted in selective increased phospho-p38 levels, which in turn resulted in the observed initiation of apoptosis in trigenic mutant embryos. Taken together, these data demonstrate that tightly regulated TGFβ superfamily signaling is essential for normal craniofacial and cardiac NCC colonization and cell survival in vivo.

Zebrafish (Danio rerio) show a unique pigmentation pattern comprised of three pigment cell types: melanophores, iridophores and xanthophores. Other pigmented cells include the retinal pigmented epithelium (rpe) which absorbs excess light in the eye and maintain the extracellular environment around the photoreceptors. While previous mutations in mitfa showed a role in regulating trunk melanophores, the rpe was not affected. TALENs and CRISPR-Cas9 systems were used to generate mutant zebrafish for tfec, a transcription factor expressed in both neural crest and rpe. Embryos with tfec mutations showed a loss of iridophore pigmentation, and delays in the pigmentation of xanthophores and rpe, showing positive regulation of multiple pigment cells. Double mutants for tfec and mitfa displayed greater losses of iridophore, xanthophore and rpe pigmentation with noncircular globes, suggesting cooperative roles for these transcription factors.

PhD, Faculty of Health Sciences, University of the Witwatersrand / While ethanol is recognised beyond doubt as a teratogen to the unborn fetus, research nevertheless continues in order to understand its mode of action and its effects at the cellular level. The present study aimed to investigate the effect of an acute dose of ethanol on cranial morphology and morphometry in mouse fetuses, as well as on the morphology, migration and the expression of cell migration related genes in cultured chick cranial neural crest cells (cNCCs). Thirteen pregnant C57/BL mice were orally administered with 0.03ml/g of 25% (v/v) ethanol daily on gestational days (GD) 6, 7 and 8. Ten control animals received an identical dose of saline. On GD 18, all mice dams were killed and their fetuses were removed. Fetal morphological observations and crown-rump lengths were evaluated as were mean litter size, survival rate, birth weight and cranial dimensions. Cranial neural crest cells (cNCCs) were cultured from Potchefstroom koek koek stages 8-10 (HH) chick embryo neural tubes either in culture medium (DMEM) to which 0.2%, 0.3% and 0.4% ethanol (v/v) respectively, was added (treated) or in DMEM only (controls). Whole-mount HNK-1 immunocytochemistry was performed on treated and control chick embryos, as was an assay for caspase-dependent apoptosis. Photographs were taken of the cultures and the distance which the neural crest cells migrated from the neural tube at 24 and 48 hrs post-culture was measured. 24-hr time-lapse video microscopy recordings were also made to analyse the migration of the neural crest cells. Rhodamine-phalloidin immunocytochemistry for the actin cytoskeleton and scanning electron microscopy of surface ultrastructure were performed on migrating treated and non-treated cNCCs, as were proliferation assays and quantitative PCR of cNCCs‟ β-actin, Rac 1, Rho B and slug genes. There was a statistically significant increase in fetal reabsorption as well as a significantly reduced fetal survival rate observed in newborn mice fetuses that had been exposed to ethanol in utero compared to control fetuses. Ethanol-exposed mice showed a number of abnormalities, which were not significantly increased over vi controls (p>0.5). Birth weight, crown-rump length and mandibular length were also not significantly different in treated fetuses compared to controls (p>0.5). Treated (0.3%) chick cNCCs migrated over a significantly increased distance at both 24hrs and 48hrs compared to controls (p<0.05) in the axes of migration that were studied. The migratory distances of cNCCs derived from embryonic stage 9 (HH) were markedly affected by treatment with alcohol. The actin cytoskeleton of treated cNCCs showed disorganisation and loss of focal adhesion contacts while Rac 1, Rho B and slug genes were either up-regulated or down-regulated depending on the ethanol dose and duration of treatment. Ethanol promotes significant proliferation in cNCCs and may affect their migration by altering the expression of migration-linked genes and the arrangement of the actin cytoskeleton.

by Chan Wood-yee. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1987. / Includes bibliographical references.