Analysis on gene expression involved in migration and differentiation of cranial neural crest cells

通过分子和细胞分析，阐明与哺乳动物颅神经脊细胞迁移和分化有关的基因表达。1.Pax-6基因在脑神经脊细胞迁移过程中的表达我曾报道，在具有Pax-6基因突变的纯合子突变大鼠胚胎中，中脑脊细胞向额鼻区的迁移受到损害。为了详细检测Pax-6基因在脑神经脊移行过程中的表达，用非放射性同位素标记的探针在切片和整体上进行了原位杂交。结论：1.Pax-6基因在脑神经脊细胞本身中不表达，提示Pax-6基因产物具有介导环境因素参与控制中脑脊迁移的作用。视黄酸对微团培养小鼠面部间充质细胞软骨形成的影响如前所述，视黄酸诱导的颅面部畸形具有阶段性，不同亚型的视黄酸受体基因在来源于脑神经脊部的面部间充质的软骨形成区和非软骨形成区表达。为了阐明维甲酸是否通过其受体影响软骨的形成，从第11天小鼠胚胎分离的面部间充质细胞进行微质量培养，并在体外培养软骨分化。在不同的面原基培养中观察到不同程度的软骨形成，维甲酸抑制软骨形成呈剂量依赖关系。这些结果结合维甲酸受体基因表达的区域特异性，提示维甲酸参与了面部间充质细胞的软骨形成。

Molecular and cellular analyzes were performed to elucidate gene expression involved in migration and differentiation of mammalian cranial neural crest cells. The major achievement obtained in this year is as follows :1. Expression of Pax-6 gene during migration of cranial neural crest cellsI have previously reported that migration of midbrain crest cells toward the frontonasal mass is impaired in homozygous mutant rat embryos which have mutation in Pax-6 gene. In order to examine Pax-6 gene expression in detail during cranial neural crest migration, in situ hybridization on sections and whole mounts using non-radioisotope labeled probes was established. Pax-6 gene was not expressed in cranial neural crest cells themselves ; thereby suggeseting that Pax-6 gene product has role in mediating environmental factors that are involved in controling midbrain crest migration.2. Effects of retinoic acid on hondrogenesis of mouse facial mesenchmal cells under micromass cultureAs previously described, retinoic acid induce craniofacial malformations stage dependently and different subtypes of retinoic acid receptor gene are expressed in chondrogenic and non-chondrogenic regions of facial mesenchyme derived from the cranial neural crest. To elucidate whether retinoic acid madiates chondrogenesis via its receptors, micromass culture was carried out using facial mesenchymal cells isolated from day 11 mouse embryos, and cartilage differentiation was reproduced in vitro. Different levels of chondrogenesis were observed among cultures of individual facial primordia, and retinoic acid inhibited cartilage formation dose-dependently. These results together with region-specificity of retinoic acid receptor gene expression, retinoic acid is suggested to be involved in chondrogenesis of facial mesenchymal eclls.