New gain-of-function mutation shows CACNA1D as recurrently mutated gene in autism spectrum disorders and epilepsy

CACNA1D encodes the pore-forming alpha 1-subunit of Cav1.3, an L-type voltage-gated Ca2+-channel. Despite the recent discovery of two de novo missense gain-of-function mutations in Cav1.3 in two individuals with autism spectrum disorder (ASD) and intellectual disability CACNA1D has not been considered a prominent ASD-risk gene in large scale genetic analyses, since such studies primarily focus on likely-disruptive genetic variants. Here we report the discovery and characterization of a third de novo missense mutation in CACNA1D (V401L) in a patient with ASD and epilepsy. For the functional characterization we introduced mutation V401L into two major C-terminal long and short Cav1.3 splice variants, expressed wild-type or mutant channel complexes in tsA-201 cells and performed whole-cell patch-clamp recordings. Mutation V401L, localized within the channel's activation gate, significantly enhanced current densities, shifted voltage dependence of activation and inactivation to more negative voltages and reduced channel inactivation in both Cav1.3 splice variants. Altogether, these gating changes are expected to result in enhanced Ca2+-influx through the channel, thus representing a strong gain-of-function phenotype. Additionally, we also found that mutant channels retained full sensitivity towards the clinically available Ca2+-channel blocker isradipine. Our findings strengthen the evidence for CACNA1D as a novel candidate autism risk gene and encourage experimental therapy with available channel-blockers for this mutation. The additional presence of seizures and neurological abnormalities in our patient define a novel phenotype partially overlapping with symptoms in two individuals with PASNA (congenital primary aldosteronism, seizures and neurological abnormalities) caused by similar Cav1.3 gain-of-function mutations

CaV1.3 L-type Ca2+ channel contributes to the heartbeat by generating a dihydropyridine-sensitive persistent Na+ current

International audienceThe spontaneous activity of sinoatrial node (SAN) pacemaker cells is generated by a functional interplay between the activity of ionic currents of the plasma membrane and intracellular Ca2+ dynamics. The molecular correlate of a dihydropyridine (DHP)-sensitive sustained inward Na+ current (I st), a key player in SAN automaticity, is still unknown. Here we show that I st and the L-type Ca2+ current (I Ca,L) share CaV1.3 as a common molecular determinant. Patch-clamp recordings of mouse SAN cells showed that I st is activated in the diastolic depolarization range, and displays Na+ permeability and minimal inactivation and sensitivity to I Ca,L activators and blockers. Both CaV1.3-mediated I Ca,L and I st were abolished in CaV1.3-deficient (CaV1.3-/-) SAN cells but the CaV1.2-mediated I Ca,L current component was preserved. In SAN cells isolated from mice expressing DHP-insensitive CaV1.2 channels (CaV1.2DHP-/-), I st and CaV1.3-mediated I Ca,L displayed overlapping sensitivity and concentration-response relationships to the DHP blocker nifedipine. Consistent with the hypothesis that CaV1.3 rather than CaV1.2 underlies I st, a considerable fraction of I Ca,L was resistant to nifedipine inhibition in CaV1.2DHP-/- SAN cells. These findings identify CaV1.3 channels as essential molecular components of the voltage-dependent, DHP-sensitive I st Na+ current in the SAN

Ca(V)1.2 and Ca(V)1.3 channel hyperactivation in mouse islet beta cells exposed to type 1 diabetic serum

The voltage-gated Ca2+ (Ca-V) channel acts as a key player in beta cell physiology and pathophysiology. beta cell Ca-V channels undergo hyperactivation subsequent to exposure to type 1 diabetic (T1D) serum resulting in increased cytosolic free Ca2+ concentration and thereby Ca2+-triggered beta cell apoptosis. The present study was aimed at revealing the subtypes of Ca(V)1 channels hyperactivated by T1D serum as well as the biophysical mechanisms responsible for T1D serum-induced hyperactivation of beta cell Ca(V)1 channels. Patch-clamp recordings and single-cell RT-PCR analysis were performed in pancreatic beta cells from Ca(V)1 channel knockout and corresponding control mice. We now show that functional Ca(V)1.3 channels are expressed in a subgroup of islet beta cells from Ca(V)1.2 knockout mice (Ca(V)1.2(-/-)). T1D serum enhanced whole-cell Ca-V currents in islet beta cells from Ca(V)1.3 knockout mice (Ca(V)1.3(-/-)). T1D serum increased the open probability and number of functional unitary Ca(V)1 channels in Ca(V)1.2(-/-) and Ca(V)1.3(-/-) beta cells. These data demonstrate that T1D serum hyperactivates both Ca(V)1.2 and Ca(V)1.3 channels by increasing their conductivity and number. These findings suggest Ca(V)1.2 and Ca(V)1.3 channels as potential targets for anti-diabetes therapy