EFFECT OF ANTISENSE OLIGODEOXYNUCLEOTIDES DIRECTED TO INDIVIDUAL CALMODULIN GENE TRANSCRIPTS ON THE PROLIFERATION AND DIFFERENTIATION OF PC12 CELLS

Calmodulin (CaM) is encoded by three different genes that collectively give rise to five transcripts. In the present study, we used antisens e oligodeoxynucleotides targeted to unique sequences in the transcript s from the individual CaM genes to selectively block the expression of the different genes and to investigate the roles these individual gen es play in the proliferation and nerve growth factor (NGF)-induced dif ferentiation of PC12 cells. Culturing PC12 cells in the presence of ol igodeoxynucleotide antisense to the transcripts from CaM genes I and I I caused a significant decrease in the proliferation and a significant delay in the NGF-induced differentiation of PC12 cells when compared with untreated cells and with cells treated with the corresponding ran domized oligodeoxynucleotides. However, an oligodeoxynucleotide antise nse to CaM gene III did not significantly alter the proliferation or t he NGF-induced differentiation of PC12 cells. The inhibition of cell p roliferation could be reversed by washing out the antisense oligodeoxy nucleotides. The levels of CaM in cells treated with oligodeoxynucleot ides antisense to CaM genes I or II were reduced 52% or 63%, respectiv ely, of the levels found in the control cells. However, the levels of CaM were not significantly reduced in PC12 cells treated with CaM gene III antisense oligodeoxynucleotide. None of the randomized oligodeoxy nucleotides had any effect on the levels of CaM in PC12 cells, The red uced levels of CaM in PC12 cells treated with an oligodeoxynucleotide antisense to CaM gene I were accompanied by a reduction in the levels of the CaM gene I mRNAs, supporting a true antisense mechanism of acti on for these oligodeoxynucleotides. These results suggest that alterin g the level of CaM by using antisense oligodeoxynucleotides targeted t o the dominant CaM transcripts in a particular cell type will specific ally inhibit their proliferation and, in the case of neuronal cells, a lter the course of their differentiation.