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Robert E. Poelmann - One of the best experts on this subject based on the ideXlab platform.
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Cardiac outflow tract malformations in chick embryos exposed to homocysteine.
Cardiovascular Research, 2004Co-Authors: Marit J. Boot, Régine P.m. Steegers-theunissen, Robert E. Poelmann, Liesbeth Van Iperen, Adriana C. Gittenberger-de GrootAbstract:Objective : Increased homocysteine concentrations have been associated with cardiac outflow tract defects. It has been hypothesized that cardiac neural crest cells were the target cells in these malformations. Cardiac neural crest cells migrate from the neural tube and contribute to the condensed mesenchyme of the Aorticopulmonary Septum and outflow tract cushions of the heart. The aim of this study is to investigate the effects of homocysteine on cardiac neural crest cells in relation to heart malformations. Methods : Homocysteine was injected either into the neural tube lumen (30 μmol/l), or into the circulatory system (30 or 300 μmol/l) of chick embryos. LacZ -retroviral labeling was used to study cardiac neural crest cell migratory pathways after exposure to homocysteine. Results : Cardiac neural crest cells contributed to the Aorticopulmonary Septum of both control and homocysteine-treated embryos. However, the outflow tract of homocysteine-neural tube injected embryos displayed 60% less apoptosis and 25% reduced myocardialization. A subarterial ventricular septal defect was observed in 83% of the embryos. None of these abnormalities were observed in homcysteine-circulatory system injected embryos. Conclusion : This study demonstrates that homocysteine disturbs apoptosis and myocardialization of the outflow tract, probably by affecting the cardiac neural crest cells.
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Spatiotemporally separated cardiac neural crest subpopulations that target the outflow tract Septum and pharyngeal arch arteries.
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2003Co-Authors: Marit J. Boot, Liesbeth Van Iperen, Adriana C. Gittenberger-de Groot, Beerend P. Hierck, Robert E. PoelmannAbstract:We used lacZ-retrovirus labeling combined with neural crest ablation in chick embryos to determine whether the cardiac neural crest cells constitute one group of multipotent cells, or they emigrate from the neural tube in time-dependent groups with different fates in the developing cardiovascular system. We demonstrated that early-migrating cardiac neural crest cells (HH9 –10) massively target the Aorticopulmonary Septum and pharyngeal arch arteries, while the late-migrating cardiac neural crest cells (HH12) are restricted to the proximal part of the pharyngeal arch arteries. These results suggest a prominent role for early-migrating cells in outflow tract septation, and a function for late-migrating cells in pharyngeal arch artery remodeling. We demonstrated in cultures of neural tube explants an intrinsic difference between the early and late populations. However, by performing heterochronic transplantations we showed that the late-migrating cardiac neural crest cells were not developmentally restricted, and could contribute to the condensed mesenchyme of the Aorticopulmonary Septum when transplanted to a younger environment. Our findings on the exact timing and migratory behavior of cardiac neural crest cells will help narrow the range of factors and genes that are involved in neural crest-related congenital heart diseases. Anat Rec Part A 275A:1009 –1018, 2003. © 2003 Wiley-Liss, Inc.
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The myth of ventrally emigrating neural tube (VENT) cells and their contribution to the developing cardiovascular system
Anatomy and Embryology, 2003Co-Authors: Marit J. Boot, Liesbeth Van Iperen, Adriana C. Gittenberger-de Groot, Robert E. PoelmannAbstract:The cardiac neural crest cells are a group of cells that emigrate from the dorsal side of the neural tube during a specific time window and contribute to the pharyngeal arch arteries and the Aorticopulmonary Septum of the heart. Recent publications have suggested that another group of cells emigrating from the ventral side of the neural tube also contributes to the developing cardiovascular system. The first aim of our study was to define the specific time window of cardiac neural crest cell migration by injecting a retrovirus containing a lacZ reporter gene into a chick embryo at different stages during development. The second aim was to study the contribution of the supposed ventrally emigrating neural tube cells to the cardiovascular system using three approaches. One approach was to inject a lacZ retrovirus into the lumen of the chick hindbrain. Secondly, we injected the retrovirus into the neural tube at the position of the 10–12 somite pair. Finally, we used the chimera technique in which we transplanted a quail neural tube segment into a chick embryo. Cardiac neural crest cells were shown to emigrate from the dorsal side of the neural tube between HH9 and HH13^−. The HH13^+ neural tube has ceased to produce cardiac neural crest cells between the level of the otic placode and the fourth pair of somites. Retroviral injection directly into the chick hindbrain at HH14 resulted in 50% of the embryos with minimal labeling of the hindbrain and intense labeling of the adjacent mesenchyme, suggesting that virus was spilled. This implies that this technique is not useful for confirming the existence of ventrally emigrating cells. Both retroviral injections into the neural tube lumen at HH14 at the position of the 10–12 somite pair and the chimeras showed no signs of ventrally emigrating neural tube cells. We conclude that there is no contribution of ventral neural tube cells to the developing cardiovascular system.
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Cell origins and tissue boundaries during outflow tract development
Trends in Cardiovascular Medicine, 1995Co-Authors: Drew M. Noden, Robert E. Poelmann, Adriana C. Gittenberger-de GrootAbstract:Abstract Morphogenesis of the cardiac outflow tract and aortic sac regions requires the progressive immigration and integrated differentiation of cells having very divergent embryonic histories. Mesodermal cells originating both within and beside the developing head contribute to endocardium and myocardium. These cells, together with later arriving neural crest cells, participate in the formation of the Aorticopulmonary Septum, truncal cushions, and semilunar valves, although there is uncertainty regarding the precise contributions of each. In addition, precursors of the enveloping epicardium and coronary arteries move into the outflow tract. Defining the spatial and temporal contributions of these disparate populations and the boundaries between them as the outflow tract shifts caudally is an essential prerequisite to understanding normal heart morphogenesis as well as the etiology of outflow tract dysmorphologies.
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The distribution and characterization of HNK-1 antigens in the developing avian heart
Anatomy and Embryology, 1993Co-Authors: Theo M. Luider, Nathalie Bravenboer, Carel Meijers, Arthur W. M. Kamp, Dick Tibboel, Robert E. PoelmannAbstract:The heart originates from splanchnic mesoderm and to a lesser extent from neural crest cells. The HNK-1 monoclonal antibody is a marker for early migrating neural crest cells, but reacts also with structures which are not derived from the neural crest. We investigated whether heart structures are HNK-1 positive before neural crest cells colonize these target tissues. To that end, we determined the HNK-1 antigen expression in the developing avian heart on immunohistochemical sections and on Western blots. The HNK-1 immunoreactivity in the developing chick heart is compared with data from literature cm the localization of neural crest cells in chick/quail chimeras. Structures with neural crest contribution, including parts of the early outflow tract and the related endocardial cushions, the primordia of the semilunar valve leaflets and the Aorticopulmonary Septum were HNK-1 positive. Furthermore, other structures were HNK-1 positive, such as the atrioventricular cushions, the wall of the sinus venosus at stage HH 15 through 21, parts of the endocardium at E3, parts of the myocardium at E6, and the extracellular matrix in the myocardial base of the semilunar valves at E14. HNK-1 expression was particularly observed in morphologically dynamic regions such as the developing valves, the outflow tract cushion, the developing conduction system and the autonomie nervous system of the heart. We observed that atrioventricular endocardial cushions are HNK-1 positive. We conclude that: a HNK-1 immunoreactivity does not always coincide with the presence of neural crest cells or their derivatives; (2) the outflow tract cushions and atrioventricular endocardial cushions are HNK-1 positive before neural crest cells are expected (stage HH 19) to enter the endocardial cushions of the outflow tract; (3) the observed spatio-temporal HNK-1 patterns observed in the developing heart correspond with various HNK-1 antigens. Apart from a constant pattern of HNK-1 antigens during development, stage-dependent HNK-1 antigens were also found.
Henry M. Sucov - One of the best experts on this subject based on the ideXlab platform.
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Normal fate and altered function of the cardiac neural crest cell lineage in retinoic acid receptor mutant embryos.
Mechanisms of development, 2020Co-Authors: Xiaobing Jiang, Bibha Choudhary, Esther Merki, Kenneth R. Chien, Robert E. Maxson, Henry M. SucovAbstract:Mouse embryos lacking the retinoic acid (RA) receptors RARalpha1 and RARbeta suffer from a failure to properly septate (divide) the early outflow tract of the heart into distinct aortic and pulmonary channels, a phenotype termed persistent truncus arteriosus. This phenotype is associated with a failure in the development of the cardiac neural crest cell lineage, which normally forms the Aorticopulmonary Septum. In this study, we examined the fate of the neural crest lineage in RARalpha1/RARbeta mutant embryos by crossing with the Wnt1-cre and conditional R26R alleles, which together constitute a genetic lineage marker for the neural crest. We find that the number, migration, and terminal fate of the cardiac neural crest is normal in mutant embryos; however, the specific function of these cells in forming the Aorticopulmonary Septum is impaired. We furthermore show that the neural crest cells themselves do not utilize retinoid receptors and do not respond to RA during this process, but rather that the phenotype is cell non-autonomous for the neural crest cell lineage. This suggests that an alternative tissue in the vicinity of the outflow tract of the heart responds directly to RA, and thereby induces or permits the neural crest cell lineage to initiate Aorticopulmonary septation.
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Normal fate and altered function of the cardiac neural crest cell lineage in retinoic acid receptor mutant embryos
Mechanisms of Development, 2002Co-Authors: Xiaobing Jiang, Bibha Choudhary, Esther Merki, Kenneth R. Chien, Robert E. Maxson, Henry M. SucovAbstract:Abstract Mouse embryos lacking the retinoic acid (RA) receptors RARα1 and RARβ suffer from a failure to properly septate (divide) the early outflow tract of the heart into distinct aortic and pulmonary channels, a phenotype termed persistent truncus arteriosus. This phenotype is associated with a failure in the development of the cardiac neural crest cell lineage, which normally forms the Aorticopulmonary Septum. In this study, we examined the fate of the neural crest lineage in RARα1/RARβ mutant embryos by crossing with the Wnt1-cre and conditional R26R alleles, which together constitute a genetic lineage marker for the neural crest. We find that the number, migration, and terminal fate of the cardiac neural crest is normal in mutant embryos; however, the specific function of these cells in forming the Aorticopulmonary Septum is impaired. We furthermore show that the neural crest cells themselves do not utilize retinoid receptors and do not respond to RA during this process, but rather that the phenotype is cell non-autonomous for the neural crest cell lineage. This suggests that an alternative tissue in the vicinity of the outflow tract of the heart responds directly to RA, and thereby induces or permits the neural crest cell lineage to initiate Aorticopulmonary septation.
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Fate of the mammalian cardiac neural crest
Development, 2000Co-Authors: X. Jiang, David H. Rowitch, Philippe Soriano, Andrew P. Mcmahon, Henry M. SucovAbstract:A subpopulation of neural crest termed the cardiac neural crest is required in avian embryos to initiate reorganization of the outflow tract of the developing cardiovascular system. In mammalian embryos, it has not been previously experimentally possible to study the long-term fate of this population, although there is strong inference that a similar population exists and is perturbed in a number of genetic and teratogenic contexts. We have employed a two-component genetic system based on Cre/lox recombination to label indelibly the entire mouse neural crest population at the time of its formation, and to detect it at any time thereafter. Labeled cells are detected throughout gestation and in postnatal stages in major tissues that are known or predicted to be derived from neural crest. Labeling is highly specific and highly efficient. In the region of the heart, neural-crest-derived cells surround the pharyngeal arch arteries from the time of their formation and undergo an altered distribution coincident with the reorganization of these vessels. Labeled cells populate the Aorticopulmonary Septum and conotruncal cushions prior to and during overt septation of the outflow tract, and surround the thymus and thyroid as these organs form. Neural-crest-derived mesenchymal cells are abundantly distributed in midgestation (E9.5-12.5), and adult derivatives of the third, fourth and sixth pharyngeal arch arteries retain a substantial contribution of labeled cells. However, the population of neural-crest-derived cells that infiltrates the conotruncus and which surrounds the noncardiac pharyngeal organs is either overgrown or selectively eliminated as development proceeds, resulting for these tissues in a modest to marginal contribution in late fetal and postnatal life.
Margaret L. Kirby - One of the best experts on this subject based on the ideXlab platform.
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Factors controlling cardiac neural crest cell migration
Cell Adhesion & Migration, 2010Co-Authors: Margaret L. Kirby, Mary R. HutsonAbstract:Cardiac neural crest cells originate as part of the postotic caudal rhombencephalic neural crest stream. Ectomesenchymal cells in this stream migrate to the circumpharyngeal ridge and then into the caudal pharyngeal arches where they condense to form first a sheath and then the smooth muscle tunics of the persisting pharyngeal arch arteries. A subset of the cells continue migrating into the cardiac outflow tract where they will condense to form the Aorticopulmonary Septum. Cell signaling, extracellular matrix and cell-cell contacts are all critical for the initial migration, pauses, continued migration, and condensation of these cells. This review elucidates what is currently known about these factors.
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Model systems for the study of heart development and disease
Seminars in Cell & Developmental Biology, 2006Co-Authors: Mary R. Hutson, Margaret L. KirbyAbstract:Neural crest cells are multipotential cells that delaminate from the dorsal neural tube and migrate widely throughout the body. A subregion of the cranial neural crest originating between the otocyst and somite 3 has been called "cardiac neural crest" because of the importance of these cells in heart development. Much of what we know about the contribution and function of the cardiac neural crest in cardiovascular development has been learned in the chick embryo using quail-chick chimeras to study neural crest migration and derivatives as well as using ablation of premigratory neural crest cells to study their function. These studies show that cardiac neural crest cells are absolutely required to form the Aorticopulmonary Septum dividing the cardiac arterial pole into systemic and pulmonary circulations. They support the normal development and patterning of derivatives of the caudal pharyngeal arches and pouches, including the great arteries and the thymus, thyroid and parathyroids. Recently, cardiac neural crest cells have been shown to modulate signaling in the pharynx during the lengthening of the outflow tract by the secondary heart field. Most of the genes associated with cardiac neural crest function have been identified using mouse models. These studies show that the neural crest cells may not be the direct cause of abnormal cardiovascular development but they are a major component in the complex tissue interactions in the caudal pharynx and outflow tract. Since, cardiac neural crest cells span from the caudal pharynx into the outflow tract, they are especially susceptible to any perturbation in or by other cells in these regions. Thus, understanding congenital cardiac outflow malformations in human sequences of malformations as represented by the DiGeorge syndrome will necessarily require understanding development of the cardiac neural crest.
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Hemodynamic Changes and Compensatory Mechanisms during Early Cardiogenesis after Neural Crest Ablation in Chick Embryos
Pediatric Research, 1991Co-Authors: Linda Leatherbury, David M Connuck, Harold E Gauldin, Margaret L. KirbyAbstract:ABSTRACT: Microcinephotography was used to study early heart development in chick embryos with ablations of the neural crest known to result in persistent truncus arteriosus with associated aortic arch anomalies. The premigratory neural crest destined for the 3rd and 4th pharyngeal arches and the Aorticopulmonary Septum were ablated. When the embryos reached the looped cardiac tube stage (stage 18), 15 experimental and 15 control embryos were filmed at 100 frames/s under controlled environmental conditions. End-diastolic and end-systolic dimensions were determined for the conotruncus and presumptive right ventricle that together compose the bulbus cordis. The results showed that the shortening fractions and ejection fractions were significantly depressed in the experimental embryos. The experimental embryos exhibited dilation and decreased emptying of the ventricle. There was no difference in heart rate or stroke volume between the control and experimental embryos. Thus, the calculated cardiac output was the same in the control and experimental groups. It appeared that the experimental embryos compensated for decreased contractility by ventricular dilation. These functional compensations in very early cardiac development may play an etiologic role in the subsequent development of structural heart defects.
Marit J. Boot - One of the best experts on this subject based on the ideXlab platform.
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Cardiac outflow tract malformations in chick embryos exposed to homocysteine.
Cardiovascular Research, 2004Co-Authors: Marit J. Boot, Régine P.m. Steegers-theunissen, Robert E. Poelmann, Liesbeth Van Iperen, Adriana C. Gittenberger-de GrootAbstract:Objective : Increased homocysteine concentrations have been associated with cardiac outflow tract defects. It has been hypothesized that cardiac neural crest cells were the target cells in these malformations. Cardiac neural crest cells migrate from the neural tube and contribute to the condensed mesenchyme of the Aorticopulmonary Septum and outflow tract cushions of the heart. The aim of this study is to investigate the effects of homocysteine on cardiac neural crest cells in relation to heart malformations. Methods : Homocysteine was injected either into the neural tube lumen (30 μmol/l), or into the circulatory system (30 or 300 μmol/l) of chick embryos. LacZ -retroviral labeling was used to study cardiac neural crest cell migratory pathways after exposure to homocysteine. Results : Cardiac neural crest cells contributed to the Aorticopulmonary Septum of both control and homocysteine-treated embryos. However, the outflow tract of homocysteine-neural tube injected embryos displayed 60% less apoptosis and 25% reduced myocardialization. A subarterial ventricular septal defect was observed in 83% of the embryos. None of these abnormalities were observed in homcysteine-circulatory system injected embryos. Conclusion : This study demonstrates that homocysteine disturbs apoptosis and myocardialization of the outflow tract, probably by affecting the cardiac neural crest cells.
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Spatiotemporally separated cardiac neural crest subpopulations that target the outflow tract Septum and pharyngeal arch arteries.
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2003Co-Authors: Marit J. Boot, Liesbeth Van Iperen, Adriana C. Gittenberger-de Groot, Beerend P. Hierck, Robert E. PoelmannAbstract:We used lacZ-retrovirus labeling combined with neural crest ablation in chick embryos to determine whether the cardiac neural crest cells constitute one group of multipotent cells, or they emigrate from the neural tube in time-dependent groups with different fates in the developing cardiovascular system. We demonstrated that early-migrating cardiac neural crest cells (HH9 –10) massively target the Aorticopulmonary Septum and pharyngeal arch arteries, while the late-migrating cardiac neural crest cells (HH12) are restricted to the proximal part of the pharyngeal arch arteries. These results suggest a prominent role for early-migrating cells in outflow tract septation, and a function for late-migrating cells in pharyngeal arch artery remodeling. We demonstrated in cultures of neural tube explants an intrinsic difference between the early and late populations. However, by performing heterochronic transplantations we showed that the late-migrating cardiac neural crest cells were not developmentally restricted, and could contribute to the condensed mesenchyme of the Aorticopulmonary Septum when transplanted to a younger environment. Our findings on the exact timing and migratory behavior of cardiac neural crest cells will help narrow the range of factors and genes that are involved in neural crest-related congenital heart diseases. Anat Rec Part A 275A:1009 –1018, 2003. © 2003 Wiley-Liss, Inc.
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The myth of ventrally emigrating neural tube (VENT) cells and their contribution to the developing cardiovascular system
Anatomy and Embryology, 2003Co-Authors: Marit J. Boot, Liesbeth Van Iperen, Adriana C. Gittenberger-de Groot, Robert E. PoelmannAbstract:The cardiac neural crest cells are a group of cells that emigrate from the dorsal side of the neural tube during a specific time window and contribute to the pharyngeal arch arteries and the Aorticopulmonary Septum of the heart. Recent publications have suggested that another group of cells emigrating from the ventral side of the neural tube also contributes to the developing cardiovascular system. The first aim of our study was to define the specific time window of cardiac neural crest cell migration by injecting a retrovirus containing a lacZ reporter gene into a chick embryo at different stages during development. The second aim was to study the contribution of the supposed ventrally emigrating neural tube cells to the cardiovascular system using three approaches. One approach was to inject a lacZ retrovirus into the lumen of the chick hindbrain. Secondly, we injected the retrovirus into the neural tube at the position of the 10–12 somite pair. Finally, we used the chimera technique in which we transplanted a quail neural tube segment into a chick embryo. Cardiac neural crest cells were shown to emigrate from the dorsal side of the neural tube between HH9 and HH13^−. The HH13^+ neural tube has ceased to produce cardiac neural crest cells between the level of the otic placode and the fourth pair of somites. Retroviral injection directly into the chick hindbrain at HH14 resulted in 50% of the embryos with minimal labeling of the hindbrain and intense labeling of the adjacent mesenchyme, suggesting that virus was spilled. This implies that this technique is not useful for confirming the existence of ventrally emigrating cells. Both retroviral injections into the neural tube lumen at HH14 at the position of the 10–12 somite pair and the chimeras showed no signs of ventrally emigrating neural tube cells. We conclude that there is no contribution of ventral neural tube cells to the developing cardiovascular system.
Liesbeth Van Iperen - One of the best experts on this subject based on the ideXlab platform.
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Cardiac outflow tract malformations in chick embryos exposed to homocysteine.
Cardiovascular Research, 2004Co-Authors: Marit J. Boot, Régine P.m. Steegers-theunissen, Robert E. Poelmann, Liesbeth Van Iperen, Adriana C. Gittenberger-de GrootAbstract:Objective : Increased homocysteine concentrations have been associated with cardiac outflow tract defects. It has been hypothesized that cardiac neural crest cells were the target cells in these malformations. Cardiac neural crest cells migrate from the neural tube and contribute to the condensed mesenchyme of the Aorticopulmonary Septum and outflow tract cushions of the heart. The aim of this study is to investigate the effects of homocysteine on cardiac neural crest cells in relation to heart malformations. Methods : Homocysteine was injected either into the neural tube lumen (30 μmol/l), or into the circulatory system (30 or 300 μmol/l) of chick embryos. LacZ -retroviral labeling was used to study cardiac neural crest cell migratory pathways after exposure to homocysteine. Results : Cardiac neural crest cells contributed to the Aorticopulmonary Septum of both control and homocysteine-treated embryos. However, the outflow tract of homocysteine-neural tube injected embryos displayed 60% less apoptosis and 25% reduced myocardialization. A subarterial ventricular septal defect was observed in 83% of the embryos. None of these abnormalities were observed in homcysteine-circulatory system injected embryos. Conclusion : This study demonstrates that homocysteine disturbs apoptosis and myocardialization of the outflow tract, probably by affecting the cardiac neural crest cells.
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Spatiotemporally separated cardiac neural crest subpopulations that target the outflow tract Septum and pharyngeal arch arteries.
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2003Co-Authors: Marit J. Boot, Liesbeth Van Iperen, Adriana C. Gittenberger-de Groot, Beerend P. Hierck, Robert E. PoelmannAbstract:We used lacZ-retrovirus labeling combined with neural crest ablation in chick embryos to determine whether the cardiac neural crest cells constitute one group of multipotent cells, or they emigrate from the neural tube in time-dependent groups with different fates in the developing cardiovascular system. We demonstrated that early-migrating cardiac neural crest cells (HH9 –10) massively target the Aorticopulmonary Septum and pharyngeal arch arteries, while the late-migrating cardiac neural crest cells (HH12) are restricted to the proximal part of the pharyngeal arch arteries. These results suggest a prominent role for early-migrating cells in outflow tract septation, and a function for late-migrating cells in pharyngeal arch artery remodeling. We demonstrated in cultures of neural tube explants an intrinsic difference between the early and late populations. However, by performing heterochronic transplantations we showed that the late-migrating cardiac neural crest cells were not developmentally restricted, and could contribute to the condensed mesenchyme of the Aorticopulmonary Septum when transplanted to a younger environment. Our findings on the exact timing and migratory behavior of cardiac neural crest cells will help narrow the range of factors and genes that are involved in neural crest-related congenital heart diseases. Anat Rec Part A 275A:1009 –1018, 2003. © 2003 Wiley-Liss, Inc.
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The myth of ventrally emigrating neural tube (VENT) cells and their contribution to the developing cardiovascular system
Anatomy and Embryology, 2003Co-Authors: Marit J. Boot, Liesbeth Van Iperen, Adriana C. Gittenberger-de Groot, Robert E. PoelmannAbstract:The cardiac neural crest cells are a group of cells that emigrate from the dorsal side of the neural tube during a specific time window and contribute to the pharyngeal arch arteries and the Aorticopulmonary Septum of the heart. Recent publications have suggested that another group of cells emigrating from the ventral side of the neural tube also contributes to the developing cardiovascular system. The first aim of our study was to define the specific time window of cardiac neural crest cell migration by injecting a retrovirus containing a lacZ reporter gene into a chick embryo at different stages during development. The second aim was to study the contribution of the supposed ventrally emigrating neural tube cells to the cardiovascular system using three approaches. One approach was to inject a lacZ retrovirus into the lumen of the chick hindbrain. Secondly, we injected the retrovirus into the neural tube at the position of the 10–12 somite pair. Finally, we used the chimera technique in which we transplanted a quail neural tube segment into a chick embryo. Cardiac neural crest cells were shown to emigrate from the dorsal side of the neural tube between HH9 and HH13^−. The HH13^+ neural tube has ceased to produce cardiac neural crest cells between the level of the otic placode and the fourth pair of somites. Retroviral injection directly into the chick hindbrain at HH14 resulted in 50% of the embryos with minimal labeling of the hindbrain and intense labeling of the adjacent mesenchyme, suggesting that virus was spilled. This implies that this technique is not useful for confirming the existence of ventrally emigrating cells. Both retroviral injections into the neural tube lumen at HH14 at the position of the 10–12 somite pair and the chimeras showed no signs of ventrally emigrating neural tube cells. We conclude that there is no contribution of ventral neural tube cells to the developing cardiovascular system.
