IDENTIFICATION AND CLONING OF A TRUNCATED ISOFORM OF THE CARDIAC SODIUM-CALCIUM EXCHANGER IN THE BALB C MOUSE HEART/

A truncated isoform of the cardiac sodium-calcium exchanger (NCX1) was identified and cloned from BALB/c mouse heart. This cDNA clone has an AATAAA polyadenylation signal in the 3' untranslated region that caus ed the 3344-bp clone to stop at a premature termination site and encod e for a 940-amino acid (AA) protein, in contrast to the wild-type C57B L/6 mouse, which has a 970-AA protein. Comparing the predicted AA sequ ence of NCX1 between the two mouse strains by hydropathic plot, we fou nd that the BALB/c NCX1 protein has only 11 extracellular domains, mis sing one domain at the COOH terminal, while C57BL/6 mice have 12 extra cellular domains, similar to other species. Using the mouse mapping ge ne panel BCB, the NCX1 gene was mapped to the distal end of mouse chro mosome 17 (51.3 cM), confirming the data published from the rat probe.