Figure 1. Schematic illustration of expression regulation and function of α1A and α1ACT. The CACNA1A gene, encoding the VGCC subunit α1A, is bicistronic. The second gene product, α1ACT, is generated from the α1A transcript by a cellular IRES located within the coding region of the α1A mRNA. α1ACT is a transcription factor that regulates expression of several neuronally-expressed genes, promoting neurite outgrowth. The α1ACTSCA6 reduces viability of cells and causes cerebellar cortical atrophy in an animal model.