Ca_v3.1 splice variant expression during neuronal differentiation of Y-79 retinoblastoma cells

A decrease in transient-type calcium channel current, Ca_v3.1 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_v3.1 before and after neuronal differentiation of the Y-79 retinoblastoma cell line to investigate the potential contribution of Ca_v3.1 to Y-79 differentiation. In Ca_v3.1, 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_v3.1e was not expressed in either undifferentiated or differentiated retinoblastoma cells. Splice variants Ca_v3.1ac; Ca_v3.1bc and Ca_v3.1b were all identified in undifferentiated retinoblastoma cells, while expression of these variants in differentiated cells was restricted to the Ca_v3.1bc isoform. The carboxy terminal variant Ca_v3.1f is expressed independently of the differentiation status of retinoblastoma cells with or without Ca_v3.1d. Examination of the functional contribution of Ca_v3.1 protein to Y-79 cell differentiation revealed that in Y-79 cells transfected with Ca_v3.1 antisense oligodeoxynucleotides, knockdown of Ca_v3.1 did not alter the timecourse of differentiation or neuritogenesis. The changes in Ca_v3.1 splice variants were not required for the initiation of differentiation but may be associated with tissue-specific expression or localized alterations in Ca²⁺ signaling that are essential for establishment of the mature differentiated phenotype.