Structural variants of the neural cell adhesion molecule (N-CAM) in developing feathers.
The neural cell adhesion molecule (N-CAM) is expressed in a specific spatiotemporal pattern during feather development, suggesting that adhesion mediated by this molecule is involved in feather morphogenesis. To begin to investigate N-CAM's function in developing feathers, we determined what forms of N-CAM polypeptide are present and the distribution of polysialic acid (PSA), a carbohydrate moiety that decreases N-CAM-mediated cellular adhesion. N-CAM in skin appears as a Mr 145-kDa polypeptide compared to the 140-kDa brain N-CAM polypeptide, and is encoded by a 6.4-kb mRNA, compared to the 6.1-kb mRNA in brain. Polymerase chain reaction analysis of the exon splicing pattern of skin N-CAM shows that the 6.4-kb mRNA band represents two transcripts, with and without a 93-bp insert between exons 12 and 13. Thus, two N-CAM polypeptides are expressed in skin, but the 93-bp insert does not account for the larger size of the skin mRNAs and polypeptides. We show that the size difference of the polypeptides is instead due to N-linked oligosaccharides attached to the skin N-CAM proteins. The larger size of the skin mRNAs may be due to use of a different transcriptional start site. Staining of skin sections and wholemounts confirms previous descriptions of N-CAM in developing feathers, but reveals that N-CAM is also present at low levels on epidermal cells as early as stage 29 (E6). We find that PSA is expressed only on a subset of the cells that express N-CAM, in particular on dermal cells in the feather rudiments from stage 35-36 (E9-10) and on smooth muscle cells at the base of the filaments from stage 37 (E11) until the latest stage examined (stage 44, E18). The known effects on cell-cell adhesion of amount of N-CAM and PSA suggest that the variations we observe in skin may regulate cell-cell interactions that are important in feather development.
Marsh
R G
RG
Department of Zoology, University of Alberta, Edmonton, Canada.
Gallin
W J
WJ
D000818:Animals; D001483:Base Sequence; D015816:Cell Adhesion Molecules, Neuronal / Q000032:analysis* / Q000737:chemistry; D002642:Chick Embryo; D005241:Feathers / Q000196:embryology* / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009024:Morphogenesis; D009130:Muscle, Smooth / Q000196:embryology; D015345:Oligonucleotide Probes; D009844:Oligosaccharides / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis*; D012794:Sialic Acids / Q000032:analysis*; D012867:Skin / Q000196:embryology* / Q000378:metabolism; D014158:Transcription, Genetic
D015816:Cell Adhesion Molecules, Neuronal; D015345:Oligonucleotide Probes; D009844:Oligosaccharides; D012333:RNA, Messenger; D012794:Sialic Acids; C021319:polysialic acid