Structure of the gene for the liver cell adhesion molecule, L-CAM.

The liver cell adhesion molecule, L-CAM, mediates calcium-dependent cell-cell adhesion in early embryos and in nonneural epithelia in adult tissues. Earlier studies of cDNAs for chicken L-CAM established the amino acid sequence of the mature protein. The sequence has now been extended in the 5' direction through the precursor and signal sequences and past a consensus translation initiation site. The combined cDNAs were used to isolate genomic clones covering the entire L-CAM coding sequence. The structural gene for chicken L-CAM contains 16 exons ranging in size from 115 to over 1045 base pairs with an average size of 222 base pairs. Single exons do not correspond to known structural elements such as the signal sequence, precursor segment, internal repeats, or membrane-spanning region of L-CAM. Hybridization of restriction digests of chicken genomic DNA with cDNA and genomic probes indicated that there is a single L-CAM gene in the chicken. In contrast to genes for other cell-cell or cell-substrate adhesion molecules, there is no evidence for alternative splicing of exons in this gene.