PMC

iPSC-derived Purkinje cells. Immunostaining of iPSC-derived Purkinje cells on co-culture days 26. GRID2 was expressed in the L7⁺ dendritic spines. The scale bars represent 500 μm (upper panels) and 100 μm (lower panels)

Identification of a mutation in CACNA1G causing SCA. a Pedigree charts of families 1 and 2. Arrows indicate the probands. Filled and open symbols represent affected and unaffected individuals, respectively. Genotypes of the variant c.5144G > A are shown under the number of samples. Asterisks indicate the patients used for exome sequencing. b, c Results of linkage analysis. Arrows indicate the positions of CACNA1G. d Sanger sequencing to confirm the CACNA1G variant. The reference nucleotide G is overlapped with variant nucleotide A in the mutant sample. e Structure of Ca_V3.1 encoded by CACNA1G. The star indicates the position of the identified mutation. The mutation was located in the segment 4 (S4) of the fourth repeat. f Conservation at the location of the mutation. The nucleotide and amino acid sequences are completely conserved among vertebrates. g Haplotype analysis. From the result of SNP genotyping, the haplotypes of both families around the CACNA1G gene coincided for 360 kb

Changes in electrophysiological properties. a Representative traces of T-type VDCC currents recorded from HEK293T cells expressing wild-type (upper) or mutant (lower) Ca_V3.1. Holding potential was -60 mV. Voltage steps were applied after a hyperpolarizing prepulse to -100 mV (duration = 500 ms). b Peak current-voltage plots of VDCC currents of wild-type (blue, n = 9) and mutant (red, n = 12) Ca_V3.1. c Relative conductance-voltage plots. Each data point was calculated from data in B. The black line is a fit using the Boltzmann equation (see Methods). d Steady state inactivation-voltage plots. The voltage step to -30 mV was preceded by incremental hyperpolarizing pulses (duration = 300 ms). Data were obtained from the same cells shown in B and C. The black line is a fit using the Boltzmann equation (see ). e The decay time constants of inactivation of the Ca²⁺ current plotted against voltage steps. f The 10–90 % rise times of Ca²⁺ currents plotted against voltage steps. Data are presented as the mean ± SEM. Statistical significance was assessed by Mann-Whitney U-test. **p < 0.01, *p < 0.05