endothelin-1 and Neural-Tube-Defects

Normal septation of the cardiac outflow tract requires migration of neural crest cells from the posterior rhombencephalon to the branchial arches and developing conotruncal endocardial cushions. Proper migration of these cells is mediated by a variety of molecular cues. Adhesion molecules, such as integrins, are involved in the interaction of neural crest cells with the extracellular matrix, while cadherins allow neural crest cells to interact with each other during their migration. Pax3 appears to be important for proliferation of neural crest precursors, and connexin-43-mediated gap junction communication influences the rate of migration. Endothelin and its receptors are required for normal postmigratory differentiation. Platelet-derived growth factor and retinoic acid have roles in neural crest migration and differentiation as well. Finally, the similarity between the cardiovascular malformations seen in the DiGeorge and 22q11 deletion syndromes and animal models of neural crest deficiency has led to the examination of the role of genes located near or within the DiGeorge critical region in neural crest migration.

Topics: Animals; Aorta; Cell Adhesion Molecules; Cell Movement; Chick Embryo; Chromosomes, Human, Pair 22; Connexin 43; DiGeorge Syndrome; DNA-Binding Proteins; Endothelin-1; Extracellular Matrix Proteins; Gap Junctions; Growth Substances; Heart; Humans; Mice; Mice, Knockout; Mice, Mutant Strains; Neural Crest; Neural Tube Defects; Neurotrophin 3; Paired Box Transcription Factors; PAX3 Transcription Factor; Receptors, Growth Factor; Receptors, Retinoic Acid; Transcription Factors

The purpose of the present study was to identify the potential effect of prenatal vitamin B12 administration on retinoic acid (RA)-induced early craniofacial abnormalities in mice and to investigate the possible mechanisms by which vitamin B12 reduces malformations.. In our study, whole embryo culture was used to explore the effect of vitamin B12 on mouse embryos during the critical period of organogenesis. All embryos were exposed to 0.4 µM RA and different concentrations of vitamin B12 and scored for their growth in the branchial region at the end of a 48-hour culture period. The endothelin-1 (ET-1)/dHAND protein expression levels in the first branchial arch were investigated using an immunohistochemical method.. In the whole embryo culture, 100 and 10 µM vitamin B12 dose-dependently prevented branchial region malformations and decreased craniofacial defects by 90.5% and 77.3%, respectively. ET-1 and dHAND protein levels were significantly increased in vitamin B12-supplemented embryos compared to the RA-exposed group in embryonic branchial region.. These results suggest that vitamin B12 may prevent RA-induced craniofacial abnormalities via prevention of an RA-induced decrease of ET-1 and dHAND protein levels in the branchial region during the organogenic period. This study may shed new light on preventing craniofacial abnormalities.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Branchial Region; Craniofacial Abnormalities; Dose-Response Relationship, Drug; Embryo Culture Techniques; Embryonic Development; Endothelin-1; Facial Bones; Female; Male; Mice; Mice, Inbred ICR; Microcephaly; Neural Tube Defects; Tretinoin; Vitamin B 12; Vitamin B Complex

Heterotrimeric G proteins are well known for their roles in signal transduction downstream of G protein-coupled receptors (GPCRs), and both Galpha subunits and tightly associated Gbetagamma subunits regulate downstream effector molecules. Compared to Galpha subunits, the physiological roles of individual Gbeta and Ggamma subunits are poorly understood. In this study, we generated mice deficient in the Gbeta1 gene and found that Gbeta1 is required for neural tube closure, neural progenitor cell proliferation, and neonatal development. About 40% Gbeta1(-/-) embryos developed neural tube defects (NTDs) and abnormal actin organization was observed in the basal side of neuroepithelium. In addition, Gbeta1(-/-) embryos without NTDs showed microencephaly and died within 2 days after birth. GPCR agonist-induced ERK phosphorylation, cell proliferation, and cell spreading, which were all found to be regulated by Galphai and Gbetagamma signaling, were abnormal in Gbeta1(-/-) neural progenitor cells. These data indicate that Gbeta1 is required for normal embryonic neurogenesis.

Topics: Animals; Brain; Cell Proliferation; Down-Regulation; Embryo, Mammalian; Endothelin-1; Extracellular Signal-Regulated MAP Kinases; Gene Expression Regulation, Developmental; GTP-Binding Protein beta Subunits; Heterotrimeric GTP-Binding Proteins; Lysophospholipids; Mice; Mice, Knockout; Mutagenesis, Insertional; Neural Tube Defects; Neurogenesis; Neurons; Phosphorylation; Sphingosine; Stem Cells

Homocysteine affects the migration and differentiation of neural crest cells in vitro and can result in neural tube defects in vivo. Furthermore, homocysteine has been described as an important determinant in vascular disease in human adults. However, little is known about the effects of homocysteine on the development of embryonic vessels. In this study, we injected homocysteine (30 micromol/L) into the neural tube lumen of chick embryos at the time point of neural crest cell emigration, and analyzed the effects on the neural crest-derived pharyngeal arch arteries, like the brachiocephalic arteries, and the mesoderm-derived arteries, such as the dorsal aorta. By stage HH35, we observed detachment of the endothelium, decreased expression of the extracellular matrix proteins fibrillin-2, and fibronectin in the pharyngeal arch arteries, whereas the dorsal aorta was identical in homocysteine-neural tube-injected and control embryos. No effect of homocysteine on endothelin-1 mRNA expression was observed. By stage HH40, the brachiocephalic arteries of homocysteine-neural tube-injected embryos displayed a decreased lumen diameter, an increased intima- and media-thickness, and an increased number of actin layers compared with the brachiocephalic arteries in control embryos. We propose that homocysteine affects the neural crest-derived smooth muscle cells and their extracellular matrix proteins in the pharyngeal arch arteries, resulting in an abnormal smooth muscle to endothelial cell interaction, leading to endothelial cell detachment. We suggest that, as in adult life, increased homocysteine concentrations lead to vascular damage in the embryo. This prenatal damage might increase the susceptibility to develop vessel pathology later in life.

Topics: Animals; Blood Vessels; Branchial Region; Cell Adhesion; Cell Lineage; Cell Movement; Chick Embryo; Endothelin-1; Endothelium, Vascular; Extracellular Matrix; Fibrillin-2; Fibrillins; Fibronectins; Homocysteine; Microfilament Proteins; Muscle, Smooth, Vascular; Neural Crest; Neural Tube Defects; Specific Pathogen-Free Organisms