Transitional expression of neural cell adhesion molecule isoforms during chicken embryonic myogenesis.

The neural cell adhesion molecule, NCAM, is known to be expressed in chicken muscle as at least three principal molecular forms (molecular masses of 155 kDa, 145 kDa, and 120 kDa). They are generated from a single gene by alternative splicing. To distinguish these molecular species and to investigate their expressions in muscle differentiation during chicken embryonic development, we prepared antipeptide antibodies against three different domains of the NCAM. The antibody named MSD<+> was designed to detect muscle-specific domain (MSD) which was inserted into a muscle-specific NCAM by alternative splicing. The locus encompassing the MSD insertion site was detected with the antibody named MSD<->, and cytoplasmic sites near the transmembrane region were detected with the antibody named CYT. Immunoblot analysis utilizing the peptide antibodies prepared here revealed that, of three NCAMs, two isoforms, 155 kDa and 120 kDa, were recognized with the antibody MSD<+> and the same 155-kDa and the other 145-kDa molecule were recognized with the antibody CYT. The antibody MSD<-> was capable of detecting all three isoforms of the NCAM. Expression of the 120-kDa form with MSD but lacking a cytoplasmic tail increased but that of the 145-kDa form with cytoplasmic tail but lacking MSD declined during embryonic day 5 to day 18. The 155-kDa form NCAM with both MSD and cytoplasmic tail was expressed specifically and transiently during embryonic day 11 to day 14 in chick muscle; this period coincides with the period of extensive myotube formation. Thus, this largest isotype seems to play an important role in muscle differentiation.