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

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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.