Changes of the expression and distribution of retinoic acid receptors during neurogenesis in mouse embryos

Abstract

The expression and distribution of three retinoic acid receptors, α, β and γ, were investigated in the CNS of mouse embryos during development. mRNAs and proteins of RAR-β that were expressed in the spinal cord of the 12.5-day mouse embryo decreased during development but they were not decreased in the brain. The RAR-β-positive cells were already present in the ventral region of the spinal cord of 10.5-day mouse embryos, gradually appeared in the dorsal region during development and then disappeared from the spinal cord after birth. In the brain, RAR-β-positive cells were detected in the mesencephalon and rhombencephalon but not in the telencephalon of the 12.5-day mouse embryos. RAR-β-positive cells were present in the hippocampus and cingulum but not in the neocortex of 14.5-day mouse embryos. Most neurons in the hippocampus of 16.5-day mouse embryos and the cortex of newborn mice were RAR-β-positive. In the spinal cord, RAR-α mRNAs and proteins also decreased during development but more gradually than RAR-β mRNAs and proteins. During development, the distributions of RAR-α and -β in the spinal cord and brain did not differ substantially. The main difference was the appearance of a subtypes of RAR-α, a 52-kDa protein, in the brain of newborn mice. On the other hand, RAR-γ proteins were only faintly detected in the spinal cord and the brain of the mice during the embryonal stages but these increased after birth. The distribution of RAR-α- or -β-positive cells were consistent with the neurogenesis during development in the spinal cord and brain.