Three genes encode identical calmodulin proteins in mammals. One possible reason for this unique situation is that it allows differential regulation of calmodulin gene expression. In order to study the promoter regions of the different genes, the 5’ ends of three mouse calmodulin cDNAs were isolated using a modified 5’ Rapid Amplification of cDNA Ends (RACE) method. Using these cDNAs as probes, the promoter regions of the Cam I and Cam III genes as well as a Cam II pseudogene were isolated from a 129SVJ mouse genomic library. When the Cam II cDNA was used to determine the chromosomal location of the Cam II gene, the results indicated that at least two likely pseudogenes exist in addition to the functional gene. Using a probe that contained only sequence from the promoter region and first intron of the Cam II gene, the chromosomal location of the bona fide Cam II gene was identified.

Evidence indicates that conflicting growth signals in cells can lead to apoptosis. To determine if calmodulin, a proliferation signal, would induce apoptosis in cells cultured in differentiation conditions, C2C12 myoblasts were transiently transfected with a calmodulin expression vector. Half of the transfected cells were treated with calcium ionophore to determine if the calcium levels would have an effect. Overexpression of calmodulin did not lead to apoptosis, and the calcium ionophore caused death of the control- and calmodulin-transfected cells.