KCNQ1 Research Articles

Modulation of Kv7.1/KCNE1 Channel Activity by Navβ1

KV7.1 is a voltage-gated potassium channel encoded by the gene KCNQ1. This channel is found in several organs, including the heart and the brain. In the mammalian heart, KV7.1 assembles with KCNE1 forming a channel complex that is critically important for ventricular repolarization. The activity of the KV7.1/KCNE1 complex results in the delayed rectifier current known as IKs. The voltage-gated sodium channel β type 1 subunit (NaVβ1) is also expressed in the mammalian heart. Mutations in this protein have been implicated in disorders such as epilepsy and cardiopathies, including Brugada syndrome and atrial fibrillation. The NaVβ1 subunit modulates the activity, trafficking, and expression of NaV channels. It has been shown that NaVβ1 also modulates channels from the KV1 and KV4 families, and KV7.2 channels. Preliminary data from our laboratory show that NaVβ1 modulates the activity of KV7.1. When expressed in Xenopus oocytes, KV7.1 channel-mediated K+-currents display a mild slow inactivation. These channels recover from inactivation during deactivation driven at negative voltage, displaying a “hook” like kinetics. In the presence of NaVβ1, the inactivation is remarkably enhanced, producing a strong resurgent conductance during deactivation at negative potentials. Furthermore, the deactivation rate is decreased, while activation remains seemingly unaltered. Since KV7.1, KCNE1 and NaVβ1 are expressed in the heart, we decided to investigate whether NaVβ1 could modulate KV7.1/KCNE1 activity. We found that expressing KCNE1 subunit seems to override the NaVβ1 subunit effect on KV7.1 channels. However, decreasing the relative expression of KCNE1 resulted in K+-currents that displayed features of the activity of both type of complexes. We therefore conclude that NaVβ1 can modulate the KV7.1/KCNE1 complex activity. Our work suggests that, in the heart, the interaction of KCNE1 with KV7.1 has evolved to avoid the effect of NaVβ1 on the channel, so preventing its inactivation.

Methylation levels of IGF2 and KCNQ1 in spermatozoa from infertile men are associated with sperm DNA damage.

Abnormal imprinted genes methylation in spermatozoa has been shown to be associated with subfertility. However, the relationship between sperm DNA damage and specific imprinted genes methylation remains unclear. In this study, DNA methylation levels were determined at seven imprinted genes loci (H19, INS-IGF2, KCNQ1, MEG3, MEST, PEG3 and SNRPN) in 66 semen samples using the MSRE-qPCR method. The semen samples were divided into two groups according to the threshold value (25%) of DNA fragmentation index (DFI). We found that the mean methylation level at IGF2 (cg17037101) in the group with DFI≥25% was lower than that in the group with DFI<25% (13.7±3% vs. 31.5±5.3%, p=0.0053). However, the methylation levels of other CpGs did not differ from the imprinted genes. Correlation analysis of DFI with the methylation levels of imprinted genes demonstrated that the IGF2 (cg17037101) methylation level was negatively correlated with sperm DFI (r=-0.448, p=0.0038), and the KCNQ1 (cg24932449) methylation level was positively correlated with sperm DFI (r=0.354, p=0.0273). Our results suggest that the aberrant methylation of IGF2 and KCNQ1 genes may be associated with sperm DNA damage.

Fenobucarb induces heart failure and cerebral hemorrhage in zebrafish

The potential risk and toxic mechanisms of fenobucarb (2-sec-butylphenyl methylcarbamate, BPMC) to animals and humans have not been fully elucidated. In this study, zebrafish embryos were exposed to various concentrations of BPMC from 48 hpf (hour post fertilization, hpf) to 72 hpf. We found that BPMC induced severe heart failure with bradycardia, reduced heart contractions, cardiac output and blood flow dynamics；and myocardial apoptosis. BPMC also induced cerebral hemorrhages and blood erythrocyte reduction in a dose-dependent manner. Also observed were increased ROS production and capase 9 and 3/7 activation. The mRNA levels of the ATPase-related gene (atp2a1l), calcium channel-related gene (cacna1ab), sodium channel-related gene (scn5Lab), potassium channel-related gene (kcnq1), the regulatory gene (tnnc1a) for cardiac troponin C, and several apoptosis-related genes were significantly downregulated in zebrafish following BPMC exposure. These results suggest that exposure to BPMC is a possible risk factor to cardiovascular and cerebrovascular systems in animals.

QT-prolongation and noncompaction

In a recent article, Szulik et al. reported about a 22 years old female with ventricular fibrillation, QT-prolongation, and left ventricular hypertrabeculation/noncompaction (LVHT) who died from hypoxic cerebral damage 5 days after admission [1]. We have the following comments and concerns. Patients with LVHT have a disposition for any type of cardiac arrhythmia [2,3]. This is why ventricular fibrillation not only could be due to hereditary long-QT syndrome but also due to LVHT. Ventricular fibrillation was either due to LVHT or a consequence of QT-prolongation. QT-prolongation is not unusual in LVHT and has been reported in several cases (table 1) [3-7]. LVHT has been also reported in association with long-QT-syndrome due to mutations in the KCNQ1 gene [8], in the KCNH2 gene [9], or due to an unidentified genetic defect (table 1) [10]. In a study of 105 patients with LVHT, the QT-interval increased during a mean follow up of 3.6y in 15 patients and normalized in 21 patients [11]. The increase was associated with the extension of LVHT and the presence of a neuromuscular disorder (NMD) [11].

Chapter 20 - Genetics of neonatal-onset epilepsies

Although the majority of seizures in neonates are related to acute brain injury, a substantial minority are the first symptom of a neonatal-onset epilepsy often linked to a pathogenic genetic variant. Historically, studies on neonatal seizures including treatment response and long-term consequences have lumped all etiologies together. However, etiology has been consistently shown to be the most important determinant of outcome. In the past few years, an increasing number of monogenic disorders have been described and might explain up to a third of neonatal-onset epilepsy syndromes previously included under the umbrella of Ohtahara syndrome and early myoclonic encephalopathy. In this chapter, we define the concept of genetic epilepsy and review the classification. Then, we review the most relevant monogenic neonatal-onset epilepsies, detail their underlying pathophysiologic mechanisms, and present their electroclinical phenotypes. We highlight that, in some cases, such as neonates with KCNQ2 or KCNT1 gene mutations, the early recognition of the electroclinical phenotype can lead to targeted diagnostic testing and precision medicine treatment, enabling the possibility of improved outcome.

Discovery of Novel Retigabine Derivatives as Potent KCNQ4 and KCNQ5 Channel Agonists with Improved Specificity.

Recent research suggests that KCNQ isoforms, particularly the KCNQ4 and KCNQ5 subtypes expressed in smooth muscle cells, are involved in both establishing and maintaining resting membrane potentials and regulating smooth muscle contractility. Retigabine (RTG) is a first-in-class antiepileptic drug that potentiates neuronal KCNQ potassium channels, but poor subtype selectivity limits its further application as a pharmacological tool. In this study, we improved the subtype specificity of retigabine by altering the N-1/3 substituents and discovered several compounds that show better selectivity for KCNQ4 and KCNQ5 channels. Among these compounds, 10g is highly selective for KCNQ4 and KCNQ5 channels without potentiating KCNQ1 and KCNQ2 channels. These results are an advance in the exploration of small molecule modifiers that selectively activate different KCNQ isoforms. The developed compounds could also serve as new pharmacological tools for elucidating the function of KCNQ channels natively expressed in various tissues.

Blood-Based DNA Methylation Biomarkers for Type 2 Diabetes: Potential for Clinical Applications.

Type 2 diabetes (T2D) is a leading cause of death and disability worldwide. It is a chronic metabolic disorder that develops due to an interplay of genetic, lifestyle, and environmental factors. The biological onset of the disease occurs long before clinical symptoms develop, thus the search for early diagnostic and prognostic biomarkers, which could facilitate intervention strategies to prevent or delay disease progression, has increased considerably in recent years. Epigenetic modifications represent important links between genetic, environmental and lifestyle cues and increasing evidence implicate altered epigenetic marks such as DNA methylation, the most characterized and widely studied epigenetic mechanism, in the pathogenesis of T2D. This review provides an update of the current status of DNA methylation as a biomarker for T2D. Four databases, Scopus, Pubmed, Cochrane Central, and Google Scholar were searched for studies investigating DNA methylation in blood. Thirty-seven studies were identified, and are summarized with respect to population characteristics, biological source, and method of DNA methylation quantification (global, candidate gene or genome-wide). We highlight that differential methylation of the TCF7L2, KCNQ1, ABCG1, TXNIP, PHOSPHO1, SREBF1, SLC30A8, and FTO genes in blood are reproducibly associated with T2D in different population groups. These genes should be prioritized and replicated in longitudinal studies across more populations in future studies. Finally, we discuss the limitations faced by DNA methylation studies, which include including interpatient variability, cellular heterogeneity, and lack of accounting for study confounders. These limitations and challenges must be overcome before the implementation of blood-based DNA methylation biomarkers into a clinical setting. We emphasize the need for longitudinal prospective studies to support the robustness of the current findings of this review.

Investigation of KCNQ1 polymorphisms as biomarkers for cardiovascular diseases in the Turkish Cypriots for establishing preventative medical measures

Potassium channels are important in transmitting electrical signals through potassium ions transport. These potassium channels are made from signals encoded by KCNQ1 gene. KCNQ1 polymorphisms were associated with many diseases, including many metabolic and cardiovascular diseases and therefore they can be employed as biomarkers. In this study we aimed to investigate KCNQ1 polymorphisms in the Turkish Cypriot population to reveal the allele frequencies specific for this population and use these polymorphisms as biomarkers to develop preventative medical measures.The genotypes of KCNQ1 polymorphisms (rs231361, rs231359, rs151290, rs2283228, rs2237895, rs2237896) were investigated for the first time in Turkish Cypriot population. The correlation between genotypes of these polymorphisms and plasma lipid levels in this population was also explored.The results of this study showed that there was significant differences of the allele frequencies of between rs2283228 allele of C and rs2237896 (P > 0.05) in Turkish Cypriot population. There was no association between the genotypes of the six polymorphisms and the lipid metabolism.This study is the first genetic epidemiology study that investigated the allelic frequencies of KCNQ1 polymorphisms associated with metabolic syndromes as well as cardiovascular diseases. This study proves to be crucial since the etiologic determinants and molecular pathology of cardiovascular diseases have not yet clearly understood. This study showed that genome wide association studies should be designed for preventative medicine in the Turkish Cypriot population.

Analysis of the KCNQ1 gene mutation in 2 families with congenital long QT syndrome type 1 in Xinjiang Uygur Autonomous Region

Objective: Present study analyzed the association betwen the postassium voltage-gated channel KQT-like subfamily member 1 gene (KCNQ1) mutation and the clinical and the electrocardiographic features in 2 pedigrees with congenital long QT syndrome type 1 (LQT1) in Xinjiang Uygur Autonomous Region. Methods: Three family members were diagnosed as LQT1 patients in 2 Uygur congenital LQT1 families, these 3 LQT1 patients served as long QT group, 24 Uygur healthy volunteers served as control group. Electrocardiogram (ECG) and the gene detection were applied to compare the ECG and molecular genetic features between the long QT group and control group, and to explore the relationship between the KCNQ1 gene mutation and the clinical and the electrocardiographic features in these 2 families with congenital long QT syndrome type 1. Results: The LQT1 was diagnosed in 3 cases of the 2 pedigrees. The common features of ECG were QTc>480 ms, prolonged ST segment, and delayed T wave. The gene test evidenced a polymorphism of KCNQ1 gene exon 13:47G➝A(R16R). The mutation of 133G➝A9(G45S) of exon 16 resulted in the change of the original glycine (G) to serine (s). The ECG of the control group were normal, and there were no KCNQ1 gene mutations in control group. Conclusion: The exon sequencing results of KCNQ1 gene in 2 Xinjiang Uygur congenital long LQT1 families showed that exon16 missense changes (133G to A (G45S)) can lead to amino acid mutation, this mutation may be a pathogenic mutation. Subsequent validation of the expanded sample will provide a reference for revealing the relationship between the KCNQ1 gene and the pathogenesis of LQT1.

KCNQ1 Polymorphism and Susceptibility to Sudden Cardiac Death in Chinese Population

Background: SCD (Sudden Cardiac Death) occurs commonly in forensic practice and often shows negative anatomy results after a systemic autopsy. In recent years, the importance of genetic background has been emphasized in the examination of SCD. The aim of this study is to establish a feasible method to detect SCD-related mutations located in a SCD-causing gene, potassium voltage-gated channel gene (KCNQ1). This method will meet the requirement of mutation screening for SCD in regular forensic DNA laboratories. Methods: 51 reported single nucleotide polymorphisms (SNPs) from KCNQ1 gene were selected in our study. We examined 60 SCD victims and 60 healthy individuals from the Chinese population residing in Shanxi and Chongqing, China. We performed multiplex PCR for 16 DNA fragments, then using SNaPshot reaction and capillary electrophoresis to obtain the typing results of 51 SNPs. Finding: Four previously reported coding variants were identified in our study: S546S, I145I, P448R and G643S. The allele frequencies of I145I did not differ significantly in the SCD cases compared with Chinese controls (I145I: 10% in SCD cases vs 6% in controls, p=0*301, OR=0*965). The heterozygous mutation of G643S and P448R probably were putative causative mutation for SCD in Chinese population (G643S: 40% in SCD cases vs 10% in controls, p<0*0001, OR=4*000; For P448R: 35% in SCD cases vs 8*3% in controls, p<0*001, OR=4*200). S546S was the 4th mutation found in SCD population resulting in 35% in SCD cases and 18*3% in controls (p=0*049, OR=0*883). Interpretation: The missense mutation of KCNQ1 gene, P448R and G643S, were associated with SCD susceptibility level in Chinese population. The established system would be potentially helpful for investigating the characteristic of SCD-related mutations in KCNQ1 gene. These methods are compatible with current techniques and equipments in forensic DNA laboratory and will help screen mutations in those dead of SCD and their relatives. Funding Statement: This work was supported by the Natural Science Foundation of China (No. 30900593), the Natural Science Foundation of Shanxi Province, China (No. 201601D011091), Scientific Research Foundation for Returned Overseas Chinese Scholars of Shanxi Province (2011-172) and Shanxi Scholarship Council of China (2016-055). Declaration of Interests: The authors have no financial or commercial conflicts of interest. Ethics Approval Statement: The sample collection was approved by the ethics committee of Shanxi Medical University, China. Written informed consent was obtained from participants or their family members, who agreed to use the data for this study.

Intragenic duplication of KCNQ5 gene results in aberrant splicing leading to a premature termination codon in a patient with intellectual disability

The KCNQ5 gene, widely expressed in the brain, encodes a voltage-gated potassium channel (Kv7.5) important for neuronal function. Here, we report a novel KCNQ5 intragenic duplication at 6q13 spanning about 239 Kb of genomic DNA, identified by array comparative genomic hybridization (array-CGH). The duplication was found in heterozygosity in an adult patient affected by mild intellectual disability with history of absence epilepsy in adolescence, with no EEG nor MRI alterations. By in vitro analyses we demonstrated that this copy number variation (CNV) led to an aberrant transcript with exon 2–11 skipping and a premature stop codon causing, most likely, haploinsufficiency.The Kv7.5 channel plays an important role in the regulation of M-type current and afterhyperpolarization conductances which contribute to neuronal excitability. A recently published paper described KCNQ5 missense mutations in individuals with intellectual disability and treatment-resistant epilepsy that were thought to act through either loss-of-function or gain-of-function mechanisms, associated in both cases with altered neuronal excitability.In the case reported here, we showed that no functional protein can be produced from the allele involved by the intragenic duplication. This evidence strongly supports the hypothesis of KCNQ5 haploinsufficiency, which could lead to altered neuronal excitability, thus contributing to seizure susceptibility and intellectual disability.

Identification novel LQT syndrome-associated variants in Polish population and genotype-phenotype correlations in eight families

Congenital long QT syndrome (LQTS) is a primary cardiac channelopathy. Genetic testing has not only diagnostic but also prognostic and therapeutic implications. At present, 15 genes have been associated with the disease, with most mutations located in 3 major LQTS-susceptibility genes. During a routine genetic screening for KCNQ1, KCNH2 and SCN5A genes in index cases with LQTS, seven novel variants in KCNH2 and SCN5A genes were found. Genotype-phenotype correlations were analysed in these patients and their families. An open reading frame and splice site analysis of the exons was conducted using next-generation sequencing. In novel variants, phenotypes of carriers and their affected relatives were analysed. In 39 unrelated patients, 40 pathogenic/putative pathogenic mutations were found. Thirty-three of them, predominantly missense, were reported previously: 11 were in the KCNQ, 17 in the KCNH2 and 5 in the SCN5A gene. Seven novel missense variants were found in eight families. Among them, four variants were in typical for LQTS location. Two variants in the KCNH2 gene (p.D803Y and p.D46F) and one in the SCN5A gene (G1391R) were in amino acid (AA) position which up to present has not been reported in LQTS. Phenotype analysis showed the life-threatening course of the disease in index cases with a history of sudden cardiac death in six families. Mutation carriers presented with ECG abnormalities and some of them received beta-blocker therapy. We report three novel variants (KCNQ1 p.46, KCNH2 p.D803Y, SCN5A p.G1391R) which have never been reported for this AA location in LQTS; the phenotype-genotype correlation suggests their pathogenicity.

Ancient and modern anticonvulsants act synergistically in a KCNQ potassium channel binding pocket

Epilepsy has been treated for centuries with herbal remedies, including leaves of the African shrub Mallotus oppositifolius, yet the underlying molecular mechanisms have remained unclear. Voltage-gated potassium channel isoforms KCNQ2–5, predominantly KCNQ2/3 heteromers, underlie the neuronal M-current, which suppresses neuronal excitability, protecting against seizures. Here, in silico docking, mutagenesis and cellular electrophysiology reveal that two components of M. oppositifolius leaf extract, mallotoxin (MTX) and isovaleric acid (IVA), act synergistically to open neuronal KCNQs, including KCNQ2/3 channels. Correspondingly, MTX and IVA combine to suppress pentylene tetrazole-induced tonic seizures in mice, whereas individually they are ineffective. Co-administering MTX and IVA with the modern, synthetic anticonvulsant retigabine creates a further synergy that voltage independently locks KCNQ2/3 open. Leveraging this synergy, which harnesses ancient and modern medicines to exploit differential KCNQ isoform preferences, presents an approach to developing safe yet effective anticonvulsants.

Postmortem Analysis of 4 Mutation Hotspots of KCNQ1, KCNH2, and SCN5A Genes in Sudden Unexplained Death in Southwest of China.

Long QT syndrome (LQTS) is known to be involved in some sudden unexplained death (SUD) cases. To make clear whether the pathogenic genes of LQTS are involved in SUD in Yunnan province, southwest of China, we examined 4 mutation hotspot segments of KCNQ1, KCNH2, and SCN5A genes in 83 SUD cases using polymerase chain reaction and direct DNA sequencing. Genomic DNA was extracted from paraffin-embedded tissues in 83 cases of sudden cardiac death. One novel homozygous missense variant was identified in exon 3 of KCNQ1, c. 575G>T (p.R192L) in one case. One novel heterozygous missense variant was identified in exon 7 of KCNH2, c.1789T>A (p.Y597N) in 1 case. One novel heterozygous missense variant was identified in exon 7 of KCNH2, c.1800C>A (p.S600R) in 9 cases. In addition, 18 individuals were found to have heterozygous missense variant in exon 7 of KCNH2, c.1801G>A (p.G601S). Our study suggests that some SUDs in Yunnan province may be related with the pathogenic genes of LQTS.

A variant in KCNQ1 gene predicts metabolic syndrome among northern urban Han Chinese women

BackgroundPrevious studies have reported that the potassium voltage-gated channel subfamily Q member 1 (KCNQ1) gene is associated with diabetes in both European and Asian population. This study aims to find a predictable single nucleotide polymorphism (SNP) to predict the risk of metabolic syndrome (MetS) through investigating the association of SNP in KCNQ1 gene with MetS in Han Chinese women of northern urban area.MethodsSix SNPs were selected and genotyped in 1381 unrelated women aged 21 and above, who have had physical check-up in Shandong Provincial Qianfoshan Hospital. Cox proportional model was conducted to access the association between SNPs and MetS.ResultsSixty one women developed MetS between 2010 and 2015 during the 3055 person-year of follow-up. The cumulative incidence density was 19.964/1000 person-year. The SNP rs163182 was associated with MetS both in the additive genetic model (RR = 1.658, 95% CI: 1.144–2.402) and in the recessive genetic model (RR = 2.461, 95% CI: 1.347–4.496). It remained significant after adjustment. This relationship was also observed in MetS components (BMI and SBP).ConclusionA novel association between rs163182 and MetS was found in this study, which can predict the occurrence of MetS among northern urban Han Chinese women. More investigations are needed to be done to assess the possible pathway in which KCNQ1 gene affects MetS.

Genetic variation in KCNQ4 gene is associated with susceptibility to noise-induced hearing loss in a Chinese population

Noise-induced hearing loss (NIHL), one of the most widespread occupational health risks worldwide, is a kind of complex disorder resulting from both genetic and environmental factors. KCNQ4 channels are crucial to the internal ear potassium recycling. To explore whether KCNQ4 polymorphism is associated with individual susceptibility to NIHL, we performed this genetic association study on 571 NIHL cases and 639 normal hearing controls selected from about 2700 Chinese noise-exposed workers. General information and audiometric data were obtained through questionnaires and pure-tone audiometry (PTA). DNA samples were collected and genotyping for three selected SNPs (rs709688, rs2769256 and rs4660468) was performed. Significant differences were observed between cases and controls for the genotype frequency and allele frequency in rs4660468, suggesting that rs4660468 CT/TT genotype and T allele may be risk factors for NIHL. In subjects exposed to noise for more than 16 years (OR = 1.23, 95% CI = 1.09–1.53) and those who exposed to noise >92 dB (OR = 1.29, 95% CI = 1.08–1.69), increased risks of NIHL were found after stratified analysis for rs4660468. Our results suggest that rs4660468 T allele of KCNQ4 involves with a higher risk of NIHL and could be one biomarker of susceptibility for Chinese noise exposed workers.

Transcripts of Kv7.1 and MinK channels and slow delayed rectifier K+ current (IKs) are expressed in zebrafish (Danio rerio) heart.

Zebrafish are increasingly used as a model for human cardiac electrophysiology, arrhythmias, and drug screening. However, K+ ion channels of the zebrafish heart, which determine the rate of repolarization and duration of cardiac action potential (AP) are still incompletely known and characterized. Here, we provide the first evidence for the presence of the slow component of the delayed rectifier K+channels in the zebrafish heart and characterize electrophysiological properties of the slow component of the delayed rectifier K+current, IKs. Zebrafish atrium and ventricle showed strong transcript expression of the kcnq1 gene, which encodes the Kv7.1 α-subunit of the slow delayed rectifier K+ channel. In contrast, the kcne1 gene, encoding the MinK β-subunit of the delayed rectifier, was expressed at 21 and 17 times lower level in ventricle and atrium, respectively, in comparison to the kcnq1. IKs was observed in 62% of ventricular myocytes with mean (± SEM) density of 1.23 ± 0.37 pA/pF at + 30mV.Activation rate of IKs was 38% faster (τ50 = 1248 ± 215ms) than kcnq1:kcne1channels (1725 ± 792ms) expressed in 3:1 ratio in Chinese hamster ovary cells. Microelectrode experiments demonstrated the functional relevance of IKs in the zebrafish heart, since 100μM chromanol 293B produced a significant prolongation of AP in zebrafish ventricle. We conclude that AP repolarization in zebrafish ventricle is contributed by IKs, which is mainly generated by homotetrameric Kv7.1 channels not coupled to MinK ancillaryβ-subunits. This is a clear difference to the human heart, where MinK is an essential component of the slow delayed rectifier K+channel.

Impact of KCNQ1, CDKN2A/2B, CDKAL1, HHEX, MTNR1B, SLC30A8, TCF7L2, and UBE2E2 on risk of developing type 2 diabetes in Thai population

BackgroundSeveral type 2 diabetes (T2D) susceptibility loci identified via genome-wide association studies were found to be replicated among various populations. However, the influence of these loci on T2D in Thai population is unknown. The aim of this study was to investigate the influence of eight single nucleotide polymorphisms (SNPs) reported in GWA studies on T2D and related quantitative traits in Thai population.MethodsEight SNPs in or near the KCNQ1, CDKN2A/2B, SLC30A8, HHEX, CDKAL1, TCF7L2, MTNR1B, and UBE2E2 genes were genotyped. A case-control association study comprising 500 Thai patients with T2D and 500 ethnically-matched control subjects was conducted. Associations between SNPs and T2D were examined by logistic regression analysis. The impact of these SNPs on quantitative traits was examined by linear regression among case and control subjects.ResultsFive SNPs in KCNQ1 (rs2237892), CDK2A/2B (rs108116610, SLC30A8 (rs13266634), TCF7L2 (rs7903146) and MTNR1B (rs1387153) were found to be marginally associated with risk of developing T2D, with odds ratios ranging from 1.43 to 2.02 (p = 0.047 to 3.0 × 10–4) with adjustments for age, sex, and body mass index. Interestingly, SNP rs13266634 of SLC30A8 gene reached statistical significance after correcting for multiple testing (p = 0.0003) (p < 0.006 after Bonferroni correction). However, no significant association was detected between HHEX (rs1111875), CDKAL1 (rs7756992), or UBE2E2 (rs7612463) and T2D. We also observed association between rs10811661 and both waist circumference and waist-hip ratio (p = 0.007 and p = 0.023, respectively). In addition, rs13266634 in SLC30A8 was associated with glycated hemoglobin (p = 0.018), and rs7903146 in TCF7L2 was associated with high-density lipoprotein cholesterol level (p = 0.023).ConclusionOf the eight genes included in our analysis, significant association was observed between KCNQ1, CDKN2A/2B, SLC30A8, TCF7L2, and MTNR1B loci and T2D in our Thai study population. Of these, CDKN2A/2B, SLC30A8, and TCF7L2 genes were also significantly associated with anthropometric, glycemic and lipid characteristics. Larger cohort studies and meta-analyses are needed to further confirm the effect of these variants in Thai population.

Relationship between KCNQ1 (LQT1) and KCNH2 (LQT2) gene mutations and sudden death during illegal drug use

Long QT syndrome (LQTS), a congenital genetic disorder, can cause torsades de pointes (TdP), and lethal cardiac arrhythmia may result from ingestion of cardiotoxic drugs. Methamphetamine (MP) and new psychoactive substances (NPSs) can trigger TdP due to QT prolongation, leading to sudden death. We therefore analysed variations in the LQTS-associated genes KCNQ1 (LQT1) and KCNH2 (LQT2) using cardiac blood and myocardial tissue from subjects having died suddenly during MP or NPS use to investigate the relationship between congenital genetic abnormalities and sudden death during illegal drug use. We amplified and sequenced all exons of these genes using samples from 20 subjects, half of whom had died taking MP and half after using NPSs. G643S, a KCNQ1 missense polymorphism, was significantly more common among sudden deaths involving NPSs (6 subjects) than those involving MP (1 subject) and healthy Japanese subjects (P = 0.001). Notably, synthetic cathinones were detected in 2 of 3 cases involving G643S carriers. Previous functional analyses have indicated that the G643S polymorphism in the KCNQ1 potassium channel gene causes mild IKs channel dysfunction. Our data suggest that use of NPSs, particularly synthetic cathinones, is associated with elevated risk of serious cardiac arrhythmia and sudden death for subjects carrying KCNQ1 G643S.

Diagnostic yield of targeted massively parallel sequencing in children with epileptic encephalopathy

PurposeTo report our institutional experience of targeted massively parallel sequencing (MPS) testing in children with epilepsy. MethodWe retrospectively analysed the yield of targeted epileptic encephalopathy (EE) panel of 71 known EE genes in patients with epilepsy of unknown cause, who underwent clinical triage by a group of neurologists prior to the testing. We compared cost of the EE panel approach compared to traditional evaluation in patients with identified pathogenic variants. ResultsThe yield of pathogenic variants was 28.5% (n = 30/105), highest in early onset EE <3 months including Ohtahara syndrome (52%, n = 10/19) and lowest in generalized epilepsy (0/17). Patients identified with pathogenic variants had earlier onset of seizures (median 3.6 m vs 1.1y, p < 0.001, OR 0.6/year, P < 0.02) compared to those without pathogenic variants. Pathogenic/likely pathogenic variants were found in ALDH7A1 (2), CACNA1A (1), CDKL5 (3), FOXG1 (2), GABRB3 (1), GRIN2A (1), KCNQ2 (4), KCNQ3 (1), PRRT2 (1), SCN1A (6), SCN2A (2), SCN8A (2), SYNGAP1 (1), UBE3A (2) and WWOX (1) genes. This study expands the inheritance pattern caused by KCNQ3 mutations to include an autosomal recessive severe phenotype with neonatal seizures and severe developmental delay. The average cost of etiological evaluation was less with early use of EE panel compared to the traditional investigation approach ($5990 Australian dollars (AUD) vs $13069 AUD ; p = 0.02) among the patients with identified pathogenic variants. ConclusionTargeted MPS testing is a comprehensive and economical investigation that enables early genetic diagnosis in children with EE. Careful clinical triage and selection of patients with young onset EE may maximize the yield of EE panel testing.