Molecular cloning of ssd-form neural cell adhesion molecules (N-CAMs) as the major form in Xenopus heart.

Different forms of neural cell adhesion molecule (N-CAM) are generated by alternative splicing of primary transcripts and considered to have distinct biological functions. We cloned cDNAs encoding a new form of N-CAMs from the Xenopus heart cDNA library. Comparison of the sequences with chicken and mouse N-CAMs revealed that these clones code for ssd-form N-CAM. We demonstrate by Northern blot analysis that the ssd form is the major form expressed in the Xenopus adult heart. We obtained two types of ssd-form N-CAM, which are transcripts from N-CAM 1 and N-CAM 2 genes. Both types contain muscle specific domain (MSD) but not pi domain. Northern blot analysis also indicated that this form is not expressed in adult brain, in which ld-form N-CAM is the main N-CAM expressed. It is possible that high levels of specific expression of ssd-form N-CAM are related with the differentiation of cardiac muscles.