KEY MESSAGE:Novel drought tolerance genes were identified by screening thousands of random genomic fragments from grass species in transgenic rice. Identification of agronomically important genes is a critical step for crop breeding through biotechnology. Multiple approaches have been employed to identify new gene targets, including comprehensive screening platforms for gene discovery such as the over-expression of libraries of cDNA clones. In this study, random genomic fragments from plants were introduced into rice and screened for drought tolerance in a high-throughput manner with the aim of finding novel genetic elements not exclusively limited to coding sequences. To illustrate the power of this approach, genomic libraries were constructed from four grass species, and screening a total of 50,825 transgenic rice lines for drought tolerance resulted in the identification of 12 reproducibly efficacious fragments. Of the twelve, two were from the mitochondrial genome of signal grass and ten were from the nuclear genome of buffalo grass. Subsequent sequencing and analyses revealed that the ten fragments from buffalo grass carried a similar genetic element with no significant homology to any previously characterized gene. The deduced protein sequence was rich in acidic amino acid residues in the C-terminal half, and two of the glutamic acid residues in the C-terminal half were shown to play an important role in drought tolerance. The results demonstrate that an open-ended screening approach using random genomic fragments could discover trait genes distinct from gene discovery based on known pathways or biased toward coding sequence over-expression.

Background: A sodium glucose cotransporter 2 (SGLT2) inhibitor was recently found to reduce heart failure hospitalization in the EMPA-REG OUTCOMES trial. We have hypothesized that autonomic nerve activity may be modulated by SGLT2 inhibition. The current study aims to investigate the impact of empagliflozin on sympathetic and parasympathetic nerve activity in patients with type 2 diabetes mellitus.Methods: This ongoing study is a prospective, randomized, open-label, multicenter investigation of 134 patients with type 2 diabetes mellitus. The patients are randomly allocated to receive either empagliflozin or sitagliptin with the treatment goal of the Japan Diabetes Society guidelines. Ambulatory electrocardiographic monitoring is performed at the baseline and at 12 and 24 weeks of treatment. Analyses of heart rate variability are performed using the MemCalc method, which is a combination of the maximum entropy method for spectral analysis and the non-linear least squares method for square analysis. The primary endpoint is the change in the low frequency (LF; 0.04-0.15 Hz) / high frequency (HF; 0.15-0.4 Hz) ratio from baseline to 24 weeks.Discussion: This investigation on the effect of EMPagliflozin on cardiac sYmpathetic and parasympathetic neRve activity in JapanEse pAtieNts with type 2 diabetes (EMPYREAN study) offers an important opportunity to understand the impact of SGLT2 inhibition on autonomic nerve activity in patients with type 2 diabetes.Trial Registration: UMIN Clinical Trials Registry identifier UMIN000029194. Registered 19 September 2017, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000033375

AIMS:A sodium glucose cotransporter 2 (SGLT2) inhibitor was recently found to reduce heart failure hospitalization in the EMPA-REG OUTCOME trial. We have hypothesized that autonomic nerve activity may be modulated by SGLT2 inhibition. The current study aims to investigate the impact of empagliflozin on sympathetic and parasympathetic nerve activity in patients with type 2 diabetes mellitus. METHODS AND RESULTS:This ongoing study is a prospective, randomized, open-label, multicentre investigation of 134 patients with type 2 diabetes mellitus. The patients are randomly allocated to receive either empagliflozin or sitagliptin with the treatment goal of the Japan Diabetes Society guidelines. Ambulatory electrocardiographic monitoring is performed at the baseline and at 12 and 24 weeks of treatment. Analyses of heart rate variability are conducted using the MemCalc method, which is a combination of the maximum entropy method for spectral analysis and the non-linear least squares method for square analysis. The primary endpoint is the change in the low-frequency (0.04-0.15 Hz)/high-frequency (0.15-0.4 Hz) ratio from baseline to 24 weeks. CONCLUSIONS:This investigation on the effect of EMPagliflozin on cardiac sYmpathetic and parasympathetic neRve activity in JapanEse pAtieNts with type 2 diabetes (EMPYREAN study) offers an important opportunity to understand the impact of SGLT2 inhibition on autonomic nerve activity in patients with type 2 diabetes.

BACKGROUND AND PURPOSE:Angiotensin II has been implicated in the development of various cardiovascular ailments, including cardiac hypertrophy and heart failure. The fact that inhibiting its signalling reduced the incidences of both sudden cardiac death and heart failure in several large-scale clinical trials suggests that angiotensin II is involved in increased cardiac arrhythmogenicity during the development of heart failure. However, because angiotensin II also promotes structural remodelling, including cardiomyocyte hypertrophy and cardiac fibrosis, it has been difficult to assess its direct contribution to cardiac arrhythmogenicity independently of the structural effects.EXPERIMENTAL APPROACH:We induced cardiac hypertrophy in wild-type (WT) and angiotensin II type 1a receptor knockout (AT1aR-KO) mice by transverse aortic constriction (TAC). The susceptibility to ventricular tachycardia (VT) assessed in an in vivo electrophysiological study was compared in the two genotypes. The effect of acute pharmacological blockade of AT1R on the incidences of arrhythmias was also assessed.KEY RESULTS:As described previously, WT and AT1aR-KO mice with TAC developed cardiac hypertrophy to the same degree, but the incidence of VT was much lower in the latter. Moreover, although TAC induced an increase in tyrosine phosphorylation of connexin 43, a critical component of gap junctional channels, and a reduction in ventricular levels of connexin 43 protein in both genotypes, the effect was significantly ameliorated in AT1aR-KO mice. Acute pharmacological blockade of AT1R also reduced the incidence of arrhythmias.CONCLUSIONS AND IMPLICATIONS:Our findings demonstrate that AT1aR-mediated signalling makes a direct contribution to the increase in arrhythmogenicity in hypertrophied hearts independently of structural remodelling.

Background The efficacy of pharmacological interventions to prevent sudden arrhythmic death in patients with chronic heart failure remains limited. Evidence now suggests increased ventricular expression of hyperpolarization‐activated cation (HCN) channels in hypertrophied and failing hearts contributes to their arrythmicity. Still, the role of induced HCN channel expression in the enhanced arrhythmicity associated with heart failure and the capacity of HCN channel blockade to prevent lethal arrhythmias remains undetermined. Methods and Results We examined the effects of ivabradine, a specific HCN channel blocker, on survival and arrhythmicity in transgenic mice (dnNRSF‐Tg) expressing a cardiac‐specific dominant‐negative form of neuron‐restrictive silencer factor, a useful mouse model of dilated cardiomyopathy leading to sudden death. Ivabradine (7 mg/kg per day orally) significantly reduced ventricular tachyarrhythmias and improved survival among dnNRSF‐Tg mice while having no significant effect on heart rate or cardiac structure or function. Ivabradine most likely prevented the increase in automaticity otherwise seen in dnNRSF‐Tg ventricular myocytes. Moreover, cardiac‐specific overexpression of HCN2 in mice (HCN2‐Tg) made hearts highly susceptible to arrhythmias induced by chronic β‐adrenergic stimulation. Indeed, ventricular myocytes isolated from HCN2‐Tg mice were highly susceptible to β‐adrenergic stimulation‐induced abnormal automaticity, which was inhibited by ivabradine. Conclusions HCN channel blockade by ivabradine reduces lethal arrhythmias associated with dilated cardiomyopathy in mice. Conversely, cardiac‐specific overexpression of HCN2 channels increases arrhythmogenicity of β‐adrenergic stimulation. Our findings demonstrate the contribution of HCN channels to the increased arrhythmicity seen in failing hearts and suggest HCN channel blockade is a potentially useful approach to preventing sudden death in patients with heart failure.

Backgrounds: Cardiac resynchronization therapy (CRT) is an established option for advanced heart failure (HF) with electro-mechanical dyssynchrony. However, it provides no benefit in an approximately one third of the patients, which is unpredictable by any clinical tool. We hypothesized that (1) magnetocardiography (MCG) capable of delineating ventricular conduction sequences with high spatio-temporal resolution identify heterogeneous (multi-directional) left ventricular (LV) intraventricular conduction (presumably indicative of local block) and that (2) it would hamper the CRT effect, thereby predicting poor prognosis after CRT implantation. Methods: We analyzed 64-Ch MCGs (1kHz) in 52 patients with advanced HF (LVEF 25±9%) and QRS prolongation (147±31ms) on ECG before CRT implantation. According to the QRS current arrow mapping, they were divided into Group-A with uni-directional homogeneous ventricular conduction (n=33) and Group-B with multi-directional heterogeneous ventricular conduction patterns (n=19). CRT responder was defined when LVESV decreased >15% or LVEF increased >15%. Results: Baseline LVEF, BNP, and NYHA class were comparable between the groups. After 6 months, responders were more frequently found in Group-A (27/33) than Group-B (4/19, p<0.01). More importantly, during the mean follow-up of 637 (105-2042) days, Kaplan-Meier analysis revealed a marked difference in mortality (death and LVAD implant, 0/33 in Group-A, 8/19 in Group-B, p<0.001). MCG conduction patterns and Prognosis Conclusions: Our MCG analysis indicated that prolonged but homogeneous LV conduction may represent a characteristic of the candidate who potentially benefits from CRT, while the presence of multi-directional heterogeneous conduction may negate the efficacy of CRT, thereby predicting poor prognosis after CRT implantation.

Myocardin‐related transcription factor (MRTF)‐A is a Rho signalling‐responsive co‐activator of serum response factor (SRF). Here, we show that induction of MRTF‐A expression is key to pathological vascular remodelling. MRTF‐A expression was significantly higher in the wire‐injured femoral arteries of wild‐type mice and in the atherosclerotic aortic tissues of ApoE−/− mice than in healthy control tissues, whereas myocardin expression was significantly lower. Both neointima formation in wire‐injured femoral arteries in MRTF‐A knockout (Mkl1−/−) mice and atherosclerotic lesions in Mkl1−/−; ApoE−/− mice were significantly attenuated. Expression of vinculin, matrix metallopeptidase 9 (MMP‐9) and integrin β1, three SRF targets and key regulators of cell migration, in injured arteries was significantly weaker in Mkl1−/− mice than in wild‐type mice. In cultured vascular smooth muscle cells (VSMCs), knocking down MRTF‐A reduced expression of these genes and significantly impaired cell migration. Underlying the increased MRTF‐A expression in dedifferentiated VSMCs was the downregulation of microRNA‐1. Moreover, the MRTF‐A inhibitor CCG1423 significantly reduced neointima formation following wire injury in mice. MRTF‐A could thus be a novel therapeutic target for the treatment of vascular diseases. Pathological vascular remodelling in arterial lesions such as atherosclerotic plaques coincides with increased expression of the transcription factor MRTF‐A. MRTF‐A loss ameliorates these lesions, reducing the expression of cell migration regulators. MRTF‐A therefore represents a promising therapeutic target for vascular disease.

Accumulating evidence suggests increased ventricular expression of hyperpolarization-activated cation channels (HCNs) in hypertrophied and failing hearts contributes to the induction of arrhythmias. In this study, we addressed the capacity of HCNs blockade to prevent lethal arrhythmias associated with heart failure. Transgenic mice expressing a dominant-negative mutant of neuron-restrictive silencer factor in a cardiac-specific manner (dnNRSF-Tg) exhibited dilated cardiomyopathy and sudden arrythmic death with an increase in ventricular HCNs expression, which are potentially responsible for the observed lethal arrhythmias. Ivabradine (Iva), a specific HCN channel inhibitor, significantly improved the survival among dnNRSF-Tg mice. Though echocardiographic, hemodynamic, and histological analyses showed no significant difference between Iva and control, ECG telemetric monitoring showed the significant reduction of arrhythmias in dnNRSF-Tg mice treated with Iva (VT; Iva 19/h, control 92/h ; p<0.05), suggesting that Iva improved the survival by preventing lethal arrhythmias. We also found that the transgenic mice overexpressing HCN2 specifically in the heart (HCN2-Tg) are susceptible to ventricular arrhythmias induced by chronic isoproterenol infusion. In isolated ventricular myocytes from HCN2-Tg, but not in those from wild type mice, isoproterenol induced abnormal spontaneous action potentials, which were suppressed with Iva. Our findings suggest that increased ventricular expression of HCN channels possibly contributes to the ventricular arrhythmias, and HCN channels blockade may represent a new and effective means of preventing sudden arrhythmic death in patients with heart failure.

Myocardin-related transcription factor (MRTF)-A is a Rho signaling-responsive co-activator of serum response factor (SRF). Here we show that induction of MRTF-A expression is key to pathological vascular remodeling in mouse models of vascular disease. MRTF-A expression was significantly higher in the wire-injured femoral arteries of wild-type mice and in the atherosclerotic aortic tissues of ApoE -/- mice than in healthy control tissues, whereas myocardin expression was significantly lower. In addition, neointima formation in wire-injured femoral arteries in MRTF-A knockout ( Mkl1 -/- ) mice and atherosclerotic lesions in Mkl1 -/- ;ApoE -/- mice were both significantly attenuated. Expression of vinculin, MMP-9 and integrin β1, three SRF targets and key regulators of cell migration, in injured arteries was significantly weaker in Mkl1 -/- mice than in wild-type mice. In cultured vascular smooth muscle cells (VSMCs), a cellular model of dedifferentiated VSMCs, knocking down MRTF-A reduced expression of these genes and significantly impaired cell migration. Underlying the increased MRTF-A expression in dedifferentiated VSMCs was the downregulation of microRNA-1 concomitant with a decrease in myocardin expression. Moreover, the MRTF-A inhibitor CCG1423 significantly reduced neointima formation following wire injury in mice. MRTF-A could thus be a novel therapeutic target for the treatment of vascular diseases.

Growing evidence demonstrates that the hyperpolarization-activated cyclic nucleotide gated channels (HCNs) is overexpressed in failing hearts and potentially involved in increased arrhythmogenicity. Inhibiting HCN channels could be a promising approach to preventing lethal arrhythmias associated with heart failure. Transgenic mice expressing a dominant-negative mutant of neuron-restrictive silencer factor specifically in the heart (dnNRSF-Tg) exhibit dilated cardiomyopathy and sudden arrhythmic death, accompanied with the increased ventricular HCNs expression. We examined the effects of ivabradine (Iva, 7 mg/kg/d), a specific HCN channel inhibitor on survival and arrhythmogenicity in dnNRSF-Tg and found that Iva significantly improved the survival among dnNRSF-Tg. Iva significantly reduced ventricular arrhythmias in dnNRSF-Tg in ECG telemetry analysis and isoproterenol-induced increase in spontaneous action potentials in ventricular myocytes from dnNRSF-Tg, suggesting that Iva improved the survival by preventing lethal arrhythmias. We also found that transgenic mice overexpressing HCN2 in the heart are highly susceptible to arrhythmias induced by chronic isoproterenol infusion. Our findings demonstrate the contribution of increased ventricular expression of HCNs to the increased arrhythmogenicity and define HCN inhibition by Iva as an useful therapeutic approach to preventing lethal arrhythmias.

Neuron-restrictive silencer factor (NRSF) is a zinc-finger transcription factor that binds to specific DNA sequences (NRSE) to repress transcription. By down-regulating the transcription of its target genes, NRSF contributes to the regulation of various biological processes, including neuronal differentiation, carcinogenesis and cardiovascular homeostasis. We previously reported that NRSF regulates expression of the cardiac fetal gene program, and that attenuation of NRSF-mediated repression contributes to genetic remodeling in hearts under pathological conditions. The precise molecular mechanisms and signaling pathways via which NRSF activity is regulated in pathological conditions of the heart remain unclear, however. In this study, to search for regulators of NRSF, we carried out yeast two-hybrid screening using NRSF as bait and identified zinc-finger protein (Zfp) 90 as a novel NRSF-binding protein. NRSF and Zfp90 colocalized in the nucleus, with the zinc-finger DNA-binding domain of the former specifically interacting with the latter. Zfp90 inhibited the repressor activity of NRSF by inhibiting its binding to DNA, thereby derepressing transcription of NRSF-target genes. Knockdown of Zfp90 by siRNA led to reduced expression of NRSF-target fetal cardiac genes, atrial and brain natriuretic peptide genes, and conversely, overexpression of Zfp90 in ventricular myocardium resulted in significant increases in the expression of these genes. Notably, expression of Zfp90 mRNA was significantly upregulated in mouse and human hearts with chronic heart failure. Collectively, these results suggest that Zfp90 functions as a negative regulator of NRSF and contributes to genetic remodeling during the development of cardiac dysfunction.