Characterization of a novel KCNJ2 sequence variant detected in Andersen-Tawil syndrome patients

Abstract

BackgroundMutations in the KCNJ2 gene encoding the ion channel Kir2.1 have been linked to the Andersen-Tawil syndrome (ATS). Molecular genetic screening performed in a family exhibiting clinical ATS phenotypes unmasked a novel sequence variant (c.434A > G, p.Y145C) in this gene. The aim of this study was to investigate the effect of this variant on Kir2.1 ion channel functionality.MethodsMutant as well as wild type GFP tagged Kir2.1 channels were expressed in HEK293 cells. In order to examine the effect of the new variant, electrophysiological measurements were performed using patch clamp technique. Cellular localization of the mutant in comparison to the wild type ion channel was analyzed by confocal laser scanning microscopy.ResultsThe currents of cells expressing only mutant channels or a mixture of wild type and mutant were significantly reduced compared to those expressing wild type (WT) channels (p < 0.01). Whereas WT expressing cells exhibited at −120 mV an averaged current of −4.5 ± 1.9 nA, the mutant generates only a current of −0.17 ± 0.07 nA. A co-expression of mutant and WT channel generates only a partial rescue of the WT current. Confocal laser scanning microscopy indicated that the novel variant is not interfering with synthesis and/or protein trafficking.ConclusionsThe detected sequence variant causes loss-of-function of the Kir2.1 channel and explains the clinical phenotypes observed in Andersen-Tawil syndrome patients.

Association analysis of SNPs in GRHL3, FAF1, and KCNJ2 with NSCPO sub‐phenotypes in Han Chinese

“…KCNJ2 gene that locates in 17q23 and encodes Kir2.1 are important regulators of craniofacial development. It is recognized as a disease‐causing gene for Andersen syndrome and fetal alcohol spectrum disorder, both of which exhibit craniofacial anomalies (CFAs) including cleft palate phenotype (Bates, 2013; Fernlund et al, 2013; Hosaka et al, 2003; Miyamoto et al, 2015; Plaster et al, 2001; Scheiper et al, 2017; Sun & Wan, 2018). Homozygous Kir2.1 −/− knockout mice died within 8 to 12h after birth and exhibited a cleft palate phenotype (Dahal et al, 2012; Zaritsky et al, 2000).…”

Molecular stratification of arrhythmogenic mechanisms in the Andersen Tawil syndrome

“…G144A 91 and Y145C 92 are mutations that disrupt the selectivity filter by altering the signature sequence ‘GYG’ of Kir2.1. Patients with either of these mutations manifest the classical triad of symptoms, ranging from arrhythmogenic episodes and ventricular ectopy to muscular weakness and facial dysmorphias.…”

“…Patients with either of these mutations manifest the classical triad of symptoms, ranging from arrhythmogenic episodes and ventricular ectopy to muscular weakness and facial dysmorphias. 91 , 92 In each case, mutations are inherited in an autosomal dominant form, where only one of the parents is a carrier with weak symptoms related mainly to arrhythmias and periodic paralysis. For mutations involving substitutions of G146 (pertaining also the conserved ‘GYG’ sequence motif), with the exception of G146S (which served to confirm the loss-of-function of the mutated channels), 93 only clinical cases without functional analyses have been reported.…”

Characterization of an N-terminal Nav1.5 channel variant – a potential risk factor for arrhythmias and sudden death?

“…For the functional characterization of the variant p.S106G, the mutant as well as wild type Na v 1.5 channels were expressed in human embryonic kidney (HEK) cells, cell line 293 as described previously [20]. To mimic the heterozygous state of the patient, wildtype and mutant channels were also co-transfected in a 1/1 ratio (WT/MT).…”