Identification and characterization of neuron-specific and developmentally regulated gene transcripts in the chick embryo spinal cord.

Clones corresponding to neuron-specific and developmentally regulated messenger RNA species in the chick have been isolated from a complementary DNA library prepared using polyadenylated RNA from 7-day embryonic spinal cord. The library was initially screened by differential complementary DNA hybridization procedures for clones identifying polyadenylated RNAs present in embryonic spinal cord but absent from or at low abundance in liver tissue. A high proportion of selected recombinant plasmids were found to identify different RNA species which, although present in 14-day embryonic spinal cord, could not be detected in a corresponding region of the developing chick CNS that is devoid of neuronal cell bodies, the optic nerve. The neuron-specific assignment of these mRNAs within the developing neuroectoderm was confirmed using bulk-isolated neuronal and glial-enriched cell fractions from 7-day embryonic spinal cord. In addition, several distinctive patterns of developmentally regulated expression of neuron-specific messenger RNA species have been observed in the chick spinal cord. The studies lay a foundation for detailed examination of the regional and temporal distribution and control of neuronal gene expression in the chick spinal cord during embryogenesis.