Identification of gene products expressed in the developing chick visual system: characterization of a middle-molecular-weight neurofilament cDNA.

A cDNA library enriched for transcripts that accumulate from embryonic day 7 until day 1 posthatching was constructed from poly(A)+ RNA of chick optic lobe tissue. From this library, three recombinants were isolated that correspond to neural mRNAs appearing during the major period of synaptogenesis in the retinotectal system. One of these recombinants (OZ 11) was identified as a middle-molecular weight neurofilament (NF-M) cDNA which, together with two overlapping clones, encodes part of the rod and the entire tail region of NF-M. In situ hybridization revealed NF-M mRNA to be highly expressed in regions of the chick central nervous system, which contain multipolar and/or long-projection neurons.