Isolation of IFAPa-400 cDNAs: evidence for a transient cytostructural gene activity common to the precursor cells of the myogenic and the neurogenic cell lineages.

Differentiation of neural and muscle cells is characterized by a switch in the expression of the type of intermediate filament protein subunit. In these lineages, vimentin is transiently expressed in the initial stages of development and is gradually replaced by a tissue specific protein. We have identified a giant developmentally regulated antigen (IFAPa-400) which colocalizes with vimentin in the precursor cells of the neurogenic and myogenic lineages of the chick embryo [Chabot and Vincent (1990) Dev. Brain Res. 54, 195-204; Cossette and Vincent (1991) J. Cell Sci. 98, 251-260]. Based on the expression of this protein during neurogenesis and myogenesis, we hypothesize that IFAPa-400 and vimentin define a special intermediate filament network, common to the non-differentiated cells derived from the neuroectoderm and those of the myogenic tissues. We report here the isolation and sequence of partial cDNAs encoding more than 400 amino acids of the carboxy-terminus of this protein. RNA blot analysis and in situ hybridization indicate that IFAPa-400 represents a bona fide developmentally regulated gene product. These results further confirm that IFAPa-400 mRNA transcripts are limited to the early precursor cells of both neurogenic and myogenic lineages.