Genetic Variation in KCNH2 Associated With Expression in the Brain of a Unique hERG Isoform Modulates Treatment Response in Patients With Schizophrenia
ABSTRACT Antidopaminergic drugs bind to hERG1 potassium channels encoded by the gene KCNH2, which accounts for the side effect of QT interval prolongation. KCNH2 has also been associated with schizophrenia risk, and risk alleles predict increased expression of a brain-selective isoform, KCNH2 3.1, that has unique physiological properties. The authors assessed whether genetic variation associated with KCNH2 3.1 expression influences the therapeutic effects of antipsychotic drugs.
The authors performed a pharmacogenetic analysis of antipsychotic treatment response in patients with schizophrenia using data from two independent studies: a National Institute of Mental Health (NIMH) double-blind, placebo-controlled inpatient crossover trial (N=54) and the multicenter outpatient Clinical Antipsychotic Trials in Intervention Effectiveness (CATIE) study (N=364). The KCNH2 genotype that was previously associated with increased expression of KCNH2 3.1 in the brain was treated as a predictor variable. Treatment-associated changes in symptoms were evaluated in both groups with the Positive and Negative Syndrome Scale. The authors also analyzed time to discontinuation in the olanzapine arm of the CATIE study.
In the NIMH study, individuals who were homozygous for the KCNH2 3.1 increased expression-associated T allele of rs1036145 showed significant improvement in positive symptoms, general psychopathology, and thought disturbance, while patients with other genotypes showed little change. In the CATIE study, analogous significant genotypic effects were observed. Moreover, individuals who were homozygous for the T allele at rs1036145 were one-fifth as likely to discontinue olanzapine.
These consistent findings in two markedly different treatment studies support the hypothesis that hERG1-mediated effects of antipsychotics may not be limited to their potential cardiovascular side effects but may also involve therapeutic actions related to the brainspecific 3.1 isoform of KCNH2.
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ABSTRACT: Aim: Antipsychotic efficacy biomarkers have the potential to improve outcomes in psychotic patients. This study examined the effect of SULT4A1-1 haplotype status (rs2285162 [A]-rs2285167 [G]) on olanzapine response. Patients & methods: We evaluated 87 olanzapine treated subjects from Phases 1, 1B and 2 of the CATIE trial for the impact of SULT4A1-1 status on change in Positive and Negative Syndrome Scale (PANSS) total score using two models of response. We also examined weight change. Results: SULT4A1-1-positive status correlated with superior olanzapine response in Phase 1 (p = 0.004 for model 1 and p = 0.001 for model 2) and Phases 1B/2 (p = 0.05 for model 1 and p = 0.007 for model 2). SULT4A1-1-positive subjects gained significantly less weight per month on olanzapine, 0.15 lbs, than did SULT4A1-1-negative subjects, 2.27 lbs (p = 0.04). Conclusion: This study provides a second replication of superior olanzapine response in SULT4A1-1-positive subjects compared with SULT4A1-1-negative subjects. SULT4A1-1-positive subjects treated with olanzapine also gained less weight than SULT4A1-1-negative subjects. Original submitted 19 December 2013; Revision submitted 17 March 2014.Pharmacogenomics 05/2014; 15(7):933-939. DOI:10.2217/pgs.14.54 · 3.43 Impact Factor
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ABSTRACT: The potassium voltage-gated channel KCNH2 is a well-known gene in which mutations induce familial QT interval prolongation. KCNH2 is suggested to be a risk gene for schizophrenia. Additionally, the disturbance of autonomic control, which affects the QT interval, is known in schizophrenia. Therefore, we speculate that schizophrenic patients have characteristic features in terms of the QT interval in addition to the effect of antipsychotic medication. The QT interval of patients with schizophrenia not receiving antipsychotics (n = 85) was compared with that of patients with schizophrenia receiving relatively large doses of antipsychotics (n = 85) and healthy volunteers (n = 85). The QT interval was corrected using four methods (Bazett, Fridericia, Framingham or Hodges method). In ANCOVA with age and heart rate as covariates, patients not receiving antipsychotic treatment had longer QT intervals than did the healthy volunteers, but antipsychotics prolonged the QT interval regardless of the correction method used (P<0.01). Schizophrenic patients with and without medication had a significantly higher mean heart rate than did the healthy volunteers, with no obvious sex-related differences in the QT interval. The QT interval prolongation may be manifestation of a certain biological feature of schizophrenia.PLoS ONE 06/2014; 9(6):e98555. DOI:10.1371/journal.pone.0098555 · 3.53 Impact Factor
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ABSTRACT: We conducted blinded psychiatric assessments of 26 Amish subjects (52±11 years) from four families with prevalent bipolar spectrum disorder, identified 10 potentially pathogenic alleles by exome sequencing, tested association of these alleles with clinical diagnoses in the larger Amish Study of Major Affective Disorder (ASMAD) cohort, and studied mutant potassium channels in neurons. Fourteen of 26 Amish subjects had bipolar spectrum disorder. The only candidate allele shared among them was rs78247304, a nonsynonymous variant of KCNH7 (c.1181G>A, p.Arg394His). KCNH7 c.1181G>A and nine other potentially pathogenic variants were subsequently tested within the ASMAD cohort, which consisted of 340 subjects grouped into controls subjects and affected subjects from overlapping clinical categories (bipolar 1 disorder, bipolar spectrum disorder, any major affective disorder). KCNH7 c.1181G>A had the highest enrichment among individuals with bipolar spectrum disorder (X(2)=7.3) and the strongest family-based association with bipolar 1 (P=0.021), bipolar spectrum (P=0.031), and any major affective disorder (P=0.016). In vitro, the p.Arg394His substitution allowed normal expression, trafficking, assembly, and localization of HERG3/Kv11.3 channels, but altered the steady-state voltage dependence and kinetics of activation in neuronal cells. Although our genome-wide statistical results do not alone prove association, cumulative evidence from multiple independent sources (parallel genome-wide study cohorts, pharmacological studies of HERG-type potassium channels, electrophysiological data) implicates neuronal HERG3/Kv11.3 potassium channels in the pathophysiology of bipolar spectrum disorder. Such a finding, if corroborated by future studies, has implications for mental health services among the Amish, as well as development of drugs that specifically target HERG3/Kv11.3.Human Molecular Genetics 06/2014; 23(23). DOI:10.1093/hmg/ddu335 · 6.68 Impact Factor