Detrimental proarrhythmogenic interaction of Ca2+/calmodulin-dependent protein kinase II and NaV1.8 in heart failure

An interplay between Ca2+/calmodulin-dependent protein kinase IIδc (CaMKIIδc) and late Na+ current (INaL) is known to induce arrhythmias in the failing heart. Here, we elucidate the role of the sodium channel isoform NaV1.8 for CaMKIIδc-dependent proarrhythmia. In a CRISPR-Cas9-generated human iPSC-cardiomyocyte homozygous knock-out of NaV1.8, we demonstrate that NaV1.8 contributes to INaL formation. In addition, we reveal a direct interaction between NaV1.8 and CaMKIIδc in cardiomyocytes isolated from patients with heart failure (HF). Using specific blockers of NaV1.8 and CaMKIIδc, we show that NaV1.8-driven INaL is CaMKIIδc-dependent and that NaV1.8-inhibtion reduces diastolic SR-Ca2+ leak in human failing cardiomyocytes. Moreover, increased mortality of CaMKIIδc-overexpressing HF mice is reduced when a NaV1.8 knock-out is introduced. Cellular and in vivo experiments reveal reduced ventricular arrhythmias without changes in HF progression. Our work therefore identifies a proarrhythmic CaMKIIδc downstream target which may constitute a prognostic and antiarrhythmic strategy

Additional File 3 - All significant markers and effect estimates

This file contains all significant markers and their effect estimates obtained by two different GWAS models (IBS-M and IBD-MxF)

Data from: Estimating parent-specific QTL effects through cumulating linked identity-by-state SNP effects in multiparental populations

The emergence of multiparental mapping populations enabled plant geneticists to gain deeper insights into the genetic architecture of major agronomic traits and to map quantitative trait loci (QTLs) controlling the expression of these traits. Although the investigated mapping populations are similar, one open question is whether genotype data should be modelled as identical by state (IBS) or identical by descent (IBD). Whereas IBS simply makes use of raw genotype scores to distinguish alleles, IBD data are derived from parental offspring information. We report on comparing IBS and IBD by applying two multiple regression models on four traits studied in the barley nested association mapping (NAM) population HEB-25. We observed that modelling parent-specific IBD genotypes produced a lower number of significant QTLs with increased prediction abilities compared with modelling IBS genotypes. However, at lower trait heritabilities the IBS model produced higher prediction abilities. We developed a method to estimate multiallelic QTL effects in multiparental populations from simple biallelic IBS data. This method is based on cumulating IBS-derived single-nucleotide polymorphism (SNP) effect estimates in a defined genetic region surrounding a QTL. Comparing the resulting parent-specific QTL effects with those obtained from IBD approaches revealed high accordance that could be confirmed through simulations. The method turned out to be also applicable to a barley multiparent advanced generation inter-cross (MAGIC) population. The ‘cumulation method’ represents a universal approach to differentiate parent-specific QTL effects in multiparental populations, even if no IBD information is available. In future, the method could further benefit from the availability of much denser SNP maps

Additional File 2 - All phenotype data

This file contains all phenotype data that were used for GWAS. Trait values are shown as BLUEs

Generation of iPSC-lines from two independent Takotsubo syndrome patients with recurrent Takotsubo events

The Takotsubo syndrome (TTS) is characterized by acute transient left ventricular dysfunction in the absence of obstructive coronary lesions. An enhanced β-adrenergic signaling and higher sensitivity to catecholamine-induced-toxicity were identified as mechanisms associated with TTS. It is still elusive, whether TTS patients with recurrent events show similar underlying signaling pathomechanism. Induced pluripotent stem cell (iPSC)-lines were generated from skin fibroblasts of two independent female Takotsubo syndrome patients with a severe phenotype characterized by recurrent TTS events. For reprogramming, a non-integrative plasmid technique was used. All generated iPSCs maintained full pluripotency, genomic integrity, and spontaneous in vitro and in vivo differentiation capacity

Generation of homozygous Nav_{v}1.8 knock-out iPSC lines by CRISPR Cas9 genome editing to investigate a potential new antiarrhythmic strategy

The sodium channel Na$_{v}$1.8, encoded by SCN10A, is reported to contribute to arrhythmogenesis by inducing the late I$_{Na}$ and thereby enhanced persistent Na$^{+}$ current. However, its exact electrophysiological role in cardiomyocytes remains unclear. Here, we generated induced pluripotent stem cells (iPSCs) with a homozygous SCN10A knock-out from a healthy iPSC line by CRISPR Cas9 genome editing. The edited iPSCs maintained full pluripotency, genomic integrity, and spontaneous in vitro differentiation capacity. The iPSCs are able to differentiate into iPSC-cardiomyocytes, hence making it possible to investigate the role of Na$_{v}$1.8 in the heart

Additional File 4 - Markers in complete LD

This file contains a list of all 305 SNP markers that are in complete LD to another marker and, thus, have been excluded from our study

Additional File 1 - IBS and IBD matrices

This file contains all genotype scores of the identity-by-state (IBS) and identity-by-descent (IBD) genotype matrices. Polymorphic SNP alleles originating from Barke or the wild barley donors of the NAM population HEB-25 are easily distinguishable by state. Based on the Barke reference genotype, the wild barley allele can be specified in each segregating family. To setup the IBS matrix the state of the homozygous Barke allele was coded as 0, while HEB lines that showed a homozygous wild barley genotype were assigned a value of 2. Consequently, heterozygous HEB lines were assigned a value of 1. If a SNP was monomorphic in one HEB family but polymorphic in a second family, lines of the first HEB family were assigned a genotype value of 0, since their state is not different from the Barke allele. Gaps resulting from missing genotypes (0.6% of all data points) were filled with the mean of polymorphic flanking markers, based on the map of Maurer et al. (2015). This way a complete genotype data set (IBS) was retained, which is required to carry out the following multiple regression GWAS. To convert the IBS matrix into an IBD matrix we first replaced each marker value that was monomorphic in a HEB family by an empty value. Then, the resulting gaps (44.9% of all data points) were filled with the mean of the next polymorphic flanking markers of this gap. This way we can distinguish whether the allele is inherited from the recurrent parent Barke or a wild donor across the whole NAM population. The newly assigned IBD value reflects the marker’s probability of being inherited from the wild barley donor

Additional File 5 - iSelect marker names

File containing a translation for the marker names used in Maurer et al. and the official iSelect marker names

Unraveling Genomic Regions Controlling Root Traits as a Function of Nitrogen Availability in the MAGIC Wheat Population WM-800

An ever-growing world population demands to be fed in the future and environmental protection and climate change need to be taken into account. An important factor here is nitrogen uptake efficiency (NUpE), which is influenced by the root system (the interface between plant and soil). To understand the natural variation of root system architecture (RSA) as a function of nitrogen (N) availability, a subset of the multiparent advanced generation intercross (MAGIC) winter wheat population WM-800 was phenotyped under two contrasting N treatments in a high-throughput phenotyping system at the seedling stage. Fourteen root and shoot traits were measured. Subsequently, these traits were genetically analyzed using 13,060 polymorphic haplotypes and SNPs in a genome-wide association study (GWAS). In total, 64 quantitative trait loci (QTL) were detected; 60 of them were N treatment specific. Candidate genes for the detected QTL included NRT1.1 and genes involved in stress signaling under N−, whereas candidate genes under N+ were more associated with general growth, such as mei2 and TaWOX11b. This finding may indicate (i) a disparity of the genetic control of root development under low and high N supply and, furthermore, (ii) the need for an N specific selection of genes and genotypes in breeding new wheat cultivars with improved NUpE