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5-HT2B receptor-mediated serotonin morphogenetic functions in mouse cranial neural crest and myocardiac cells
D S Choi1, S J Ward, N Messaddeq
1Institut de Génétique et de Biologie Moléculaire et Cellulaire, Université L. Pasteur de Strasbourg, CNRS, INSERM, Illkirch, France.
Abstract:
During embryogenesis, serotonin has been reported to be involved in craniofacial and cardiovascular morphogenesis. The detailed molecular mechanisms underlying these functions, however remain unknown. From mouse and human species, we have recently reported the cloning of 5-HT2B receptors which share signal transduction pathways with other 5-HT2 receptor subtypes (5-HT2A and 5-HT2C). In addition to phospholipase C stimulation, it appears that these three subtypes of receptor transduce a common serotonin-induced mitogenic activity, which could be important for cell differentiation and proliferation. We have first investigated the expression of 5-HT2 receptor mRNAs in the mouse embryo. Interestingly, a peak of 5-HT2B receptor mRNA expression was detected 8-9 days postcoitum, whereas there was only low level 5-HT2A and no 5-HT2C receptor mRNA expression at this stage. Expression of this receptor was confirmed by binding assays using a 5-HT2-specific ligand which revealed a peak of binding to membrane preparations from 9 days postcoitum embryos. In addition, whole mount in situ hybridisation and immunohistochemistry on similar stage embryos detected 5-HT2B expression in neural crest cells, heart myocardium and somites. The requirement for functional 5-HT2B receptors between 8 and 9 days postcoitum is supported by culture of embryos exposed to 5-HT2-specific ligands; 5-HT2B high-affinity antagonist such as ritanserin, induced morphological defects in the cephalic region, heart and neural tube. These antagonistic treatments interfere with cranial neural crest cell migration, induce their apoptosis, and are responsible for abnormal sarcomeric organisation of the subepicardial layer and for the absence of the trabecular cell layer in the ventricular myocardium. This report indicates for the first time that 5-HT2B receptors are actively mediating the action of serotonin on embryonic morphogenesis, probably by preventing the differentiation of cranial neural crest cells and myocardial precursor cells.
Insights
Serotonin
Area of Science:
- Developmental biology
- Molecular biology
- Neuroscience
Background:
- Serotonin's role in embryonic development is known, but molecular mechanisms are unclear.
- 5-HT2B receptors share pathways with 5-HT2A and 5-HT2C receptors, mediating serotonin-induced mitogenic activity.
- This activity is crucial for cell differentiation and proliferation during embryogenesis.
Purpose of the Study:
- To investigate the expression and function of 5-HT2B receptors during mouse embryonic development.
- To elucidate the molecular mechanisms of serotonin's action on craniofacial and cardiovascular morphogenesis.
Main Methods:
- Investigated 5-HT2 receptor mRNA expression in mouse embryos using RT-PCR.
- Confirmed receptor expression via binding assays with 5-HT2-specific ligands.
- Utilized whole mount in situ hybridization and immunohistochemistry to detect receptor localization.
- Examined effects of 5-HT2-specific ligands on embryonic development in vitro.
Main Results:
- A peak in 5-HT2B receptor mRNA expression was observed at 8-9 days postcoitum.
- 5-HT2B receptor binding peaked at 9 days postcoitum in embryonic membrane preparations.
- 5-HT2B receptors were localized in neural crest cells, heart myocardium, and somites.
- Antagonists of 5-HT2B receptors disrupted cephalic region, heart, and neural tube development, affecting neural crest cell migration and myocardial differentiation.
Conclusions:
- 5-HT2B receptors actively mediate serotonin's effects on embryonic morphogenesis.
- These receptors are critical for preventing cranial neural crest cell and myocardial precursor cell differentiation.
- Disruption of 5-HT2B receptor function leads to significant developmental defects in the embryo.