In the present study, we show that one CACNA1D mutation (p.A749G in Cav1.3 α1), which has been reported as 1 of 62 high risk–conferring mutations in a whole-exome sequencing (WES) study of patients with sporadic autism and intellectual disability (24), induces a strong increase in Cav1.3 channel function. This evidence concerns the gene CACNA1D and Intellectual disability.