Germline de novo variant F747S extends the phenotypic spectrum ofCACNA1DCa2+ channelopathies

Abstract

Germline gain-of-function missense variants in the pore-forming Cav1.3 α1-subunit (CACNA1D gene) confer high risk for a severe neurodevelopmental disorder with or without endocrine symptoms. Here we report a four weeks old new-born with the novel de novo missense variant F747S with a so far not described prominent jittering phenotype in addition to symptoms previously reported for CACNA1D mutations including developmental delay, elevated aldosterone level, and transient hypoglycemia. We confirmed the pathogenicity of this variant in whole-cell patch-clamp experiments with wild-type and F747S mutant channels heterologously expressed together with α2δ1 and cytosolic β3 or membrane-bound β2a subunits. Mutation F747S caused the quantitatively largest shift in the voltage dependence of activation (−28 mV) reported so far for CACNA1D germline mutations. It also shifted inactivation to more negative voltages, slowed the time course of current inactivation and slowed current deactivation upon repolarization with both co-expressed β-subunits. In silico modelling and molecular docking simulations revealed that this gain-of-function phenotype can be explained by formation of a novel inter-domain hydrogen bond between mutant residues S747 (IIS6) with N1145 (IIIS6) stabilizing selectively the activated open channel state. F747S displayed 2–6-fold increased sensitivity for the L-type Ca2+ channel blocker isradipine compared to wild-type. Our data confirm the pathogenicity of the F747S variant with very strong gain-of-function gating changes, which may contribute to the novel jittering phenotype. Increased sensitivity for isradipine suggests this drug for potential symptomatic off-label treatment for carriers of this mutation.

Likely Pathogenic Variants of Cav1.3 and Nav1.1 Encoding Genes in Amyotrophic Lateral Sclerosis Could Elucidate the Dysregulated Pain Pathways

“…In summary, our findings on the likely loss-of-function pathogenic variants [ 67 ] of the Ca v 1.3 encoding CACNA1D gene in ALS could be indicative of the irreversible Piezo2 microdamage-derived dysregulated or lost pain pathways in the spinal dorsal horn of ALS, although further functional analyses are needed to prove the link between the detected variants and the altered cellular functions as well.…”

Case Report: Clinical delineation of CACNA1D mutation: New cases and literature review

“…Previous studies have linked germline CACNA1D gene mutations in extended clinical phenotypes with certain (21). Heterozygous missense gain-of-function mutations are associated with neuropsychiatric disorders, developmental delay, and ASD.…”

Undiagnosed Disease Network collaborative approach in diagnosing rare disease in a patient with a mosaic CACNA1D variant

“…We investigated F767L and F767S variants using our method. F767S was included because it is a known pathogenic variant that causes gain‐of‐function activity, so structural and energetic comparisons with this variant were used to understand the extent of the effect of the F767L variant (Török et al, 2022). Briefly, the corresponding in silico variant was introduced into the system with Rosetta, followed by a relax calculation to minimize the energy of the residue backbone and sidechains within 12 Å of residue 767 (Conway et al, 2014; Tyka et al, 2011).…”

“…We investigated F767L and F767S variants using our method. F767S was included because it is a known pathogenic variant that causes gain-of-function activity, so structural and energetic comparisons with this variant were used to understand the extent of the effect of the F767L variant (Török et al, 2022).…”