Ca(v)3.1 splice variant expression during neuronal differentiation of Y-79 retinoblastoma cells.

A decrease in transient-type calcium channel current, Ca(v)3.1 protein and the mRNA encoding these channels has been reported during differentiation of human retinoblastoma cells. In this study, we examined splice variants of Ca(v)3.1 before and after neuronal differentiation of the Y-79 retinoblastoma cell line to investigate the potential contribution of Ca(v)3.1 to Y-79 differentiation. In Ca(v)3.1, alternative splicing induces variations in three cytoplasmic regions, e.g. the link between domains II and III (producing isoforms e+ and e-), the link between domains III and IV (producing isoforms a, b, ac and bc) and the carboxy terminal region (producing isoforms f and d). Our results demonstrate that Ca(v)3.1e was not expressed in either undifferentiated or differentiated retinoblastoma cells. Splice variants Ca(v)3.1ac; Ca(v)3.1bc and Ca(v)3.1b were all identified in undifferentiated retinoblastoma cells, while expression of these variants in differentiated cells was restricted to the Ca(v)3.1bc isoform. The carboxy terminal variant Ca(v)3.1f is expressed independently of the differentiation status of retinoblastoma cells with or without Ca(v)3.1d. Examination of the functional contribution of Ca(v)3.1 protein to Y-79 cell differentiation revealed that in Y-79 cells transfected with Ca(v)3.1 antisense oligodeoxynucleotides, knockdown of Ca(v)3.1 did not alter the time-course of differentiation or neuritogenesis. The changes in Ca(v)3.1 splice variants were not required for the initiation of differentiation but may be associated with tissue-specific expression or localized alterations in Ca(2+) signaling that are essential for establishment of the mature differentiated phenotype.