Development Of Hypertrophic Cardiomyopathy Research Articles

Abstract 16825: Brahma Related Gene-1 (BRG1) Protein Mediates Helpful Compensatory Response to Retard Development of Heart Failure

Background: Chromatin remodeling can modulate transcription by changing gene accessibility. Brahma Related Gene-1 (Brg1) protein, which is an adenosine triphosphate catalytic subunit that supports chromatin remodeling, has been implicated in development of hypertrophic cardiomyopathy. However, contribution of Brg1 to the development of heart failure (HF) has not been clearly elucidated. Hypothesis: We hypothesize that Brg1 mediates compensatory response to cardiac stress; therefore, loss of Brg1 function will accelerate development of HF. Methods: The myosin light chain-2 Cre/loxP system was used to produce cardiac myocyte specific deletion of Brg1(-/-) mouse model with floxed littermates as control. Results: At baseline, Brg1(-/-) hearts showed mildly reduced left ventricular ejection fraction (LVEF). Aging to 12 months caused LV dilation and further reduction of LVEF in Brg1(-/-). We used trans-aortic constriction (TAC) for pressure overload challenge and chose similarly severe TAC induced pressure gradient as indicated by similarly fast peak flow velocities across the constriction. At 2-weeks post-TAC, Brg1(-/-) hearts exhibited severely reduced LVEF, severely dilated LV, and decreased ability to thicken LV wall during systole. In contrast, control hearts did not dilate and maintained its LVEF with increased LV wall thickness. Thus, Brg1 deletion greatly diminished the heart’s ability to compensate for aging and pressure challenge, thereby accelerating development of heart failure with reduced ejection fraction (HFrEF). Separately, RNA sequence analyses of 12-months aged hearts showed Brg1 deletion caused upregulation of 810 genes including HF associated long noncoding RNA XIST and down regulation of 50 genes, while 3-months old hearts were not significantly different. Conclusion: Brg1 mediates compensatory responses that are helpful to the heart to prevent development of HF; therefore, it is a potential treatment mechanism for HF.

Cryo-EM structure of the folded-back state of human β-cardiac myosin.

A large proportion of cardiac myosin heads are sequestered in an off-state during cardiac relaxation. Increasing exertion converts these heads to an on-state that are turned off during relaxation, a process essential for proper heart function. Point mutations that shift the equilibrium towards the on-state can lead to hypercontractility and the development of hypertrophic cardiomyopathy (HCM). The off-state is equated with an inactive, folded-back structural state called the interacted-head motif (IHM). The IHM is a regulatory feature of all muscle and non-muscle class-2 myosins. The off-state is equated with an inactive, folded-back structural state called the interacted-head motif (IHM). The IHM is a regulatory feature of all muscle and non-muscle myosins from class-2. In this work we report the cryo-EM structure of the human β-cardiac myosin IHM to 3.6 Å resolution. The structure reveals that the interface stabilizing the IHM are hot spots of HCM mutations. Importantly, the cardiac myosin IHM structure is significantly different from the previously described smooth muscle myosin IHM, revealing that the IHM structure is tailored to the distinct need of a given muscle type. This work now provides the missing puzzle piece needed to fully understand the molecular basis of inherited cardiomyopathy. It also paves the way for a personalized medicine approach to the design of new molecules that influence the stability of the IHM, to properly regulate cardiac contraction.

The Effect of Growth Hormone Therapy on Cardiac Outcomes in Noonan Syndrome: Long Term Follow-up Results

Cardiac involvement is common in Noonan syndrome (NS). Concerns have been raised regarding the effect of recombinant growth hormone (rGH) use on ventricular wall thickness and a possible increased risk of cardiac side effects. This study aimed to investigate the effect of rGH on the development of hypertrophic cardiomyopathy and other cardiac findings in NS. Patients under the age of 18 years and diagnosed with NS according to the Van der Burgt criteria, were included. Patients were divided into two groups according to those receiving rGH or not at the time of obtaining cardiac measurements. Before and after the treatment, electrocardiographic and echocardiographic (ECHO) assessments were made, including interventricular septal thickness, left ventricular internal diameter, and left ventricular posterior thickness. Results were expressed as Z scores. Twenty-four NS subjects (16 boys, eight girls) were included. At the beginning of the follow up, the overall height standard deviation score was -2.56±0.94. Sixteen were on rGH. The mean rGH treatment duration was 8.3±3.8 years, and the mean dose was 0.22±0.04 mg/kg/week. The final height was 169±8.2 cm, and 10 of 11 patients who reached the final height received rGH. There was no difference between the rGH and non-rGH groups in terms of ECHO parameters pre-and post-treatment. In this cohort, there was no change in ECHO parameters on rGH and during follow-up. These results suggest that rGH is safe in NS patients with cardiac pathology under close follow-up.

Properties of Cardiac Myosin with Cardiomyopathic Mutations in Essential Light Chains

The effects of cardiomyopathic mutations E56G, M149V, and E177G in the MYL3 gene encoding essential light chain of human ventricular myosin (ELCv), on the functional properties of cardiac myosin and its isolated head (myosin subfragment 1, S1) were investigated. Only the M149V mutation upregulated the actin-activated ATPase activity of S1. All mutations significantly increased the Ca2+-sensitivity of the sliding velocity of thin filaments on the surface with immobilized myosin in the in vitro motility assay, while mutations E56G and M149V (but not E177G) reduced the sliding velocity of regulated thin filaments and F-actin filaments almost twice. Therefore, despite the fact that all studied mutations in ELCv are involved in the development of hypertrophic cardiomyopathy, the mechanisms of their influence on the actin–myosin interaction are different.

Hypokinetic hypertrophic cardiomyopathy: clinical phenotype, genetics, and prognosis.

AimsTo describe the phenotype, genetics, and events associated with the development of hypertrophic cardiomyopathy (HCM) with reduced ventricular function (HCMr). Heart failure in HCM is usually associated with preserved ejection fraction, yet some HCM patients develop impaired systolic function that is associated with worse outcomes.Methods and resultsOur registry included 1328 HCM patients from two centres in Spain and Israel. Patients with normal baseline ventricular function were matched, and a competing‐risk analysis was performed to find factors associated with HCMr development. Patient records were reviewed to recognize clinically significant events that occurred closely before the development of HCMr. Genetic data were collected in patients with HCMr. A composite of all‐cause mortality or ventricular assist device (VAD)/heart transplantation was assessed according to ventricular function. Median age was 56, and 34% were female patients. HCMr at evaluation was seen in 37 (2.8%) patients, and 46 (3.5%) developed HCMr during median follow up of 9 years. HCMr was associated with younger age of diagnosis, poor functional class, and ventricular arrhythmia. Atrial fibrillation, pacemaker implantation, and baseline left ventricular ejection fraction (LVEF) of ≤55% were significant predictors of future HCMr development, while LV obstruction predicted a lower risk. Genetic testing performed in 53 HCMr patients, identifying one or more pathogenic variant in 38 (72%): most commonly in myosin binding protein C (n = 20). Six of these patients had an additional pathogenic variant in one of the sarcomere genes. Patients with baseline HCMr had a higher risk (hazard ratio 6.4, 4.1–10.1) for the composite outcome and for the individual components. Patients who developed HCMr in the course of the study had similar mortality but a higher rate of VAD/heart transplantation compared with HCM with normal LVEF.ConclusionsHypertrophic cardiomyopathy with reduced ejection fraction is associated with heart failure and poor outcome. Arrhythmia, cardiac surgery, and device implantation were commonly documented prior to HCMr development, suggesting they may be either a trigger or the result of adverse remodelling. Future studies should focus on prediction and prevention of HCMr.

Development of a Loop-Mediated Isothermal Amplification Assay Coupled With a Lateral Flow Dipstick Test for Detection of Myosin Binding Protein C3 A31P Mutation in Maine Coon Cats.

BackgroundMyosin-binding protein C3 A31P (MYBPC3-A31P) missense mutation is a genetic deviation associated with the development of hypertrophic cardiomyopathy (HCM) in Maine Coon cats. The standard detection of the MYBPC3-A31P mutation is complicated, time-consuming, and expensive. Currently, there has been a focus on the speed and reliability of diagnostic tools. Therefore, this study aimed to develop a loop-mediated isothermal amplification assay (LAMP) coupled with a lateral flow dipstick (LFD) test to detect MYBPC3-A31P mutations in Maine Coon cats.Materials and MethodsFifty-five Maine Coon cats were enrolled in this study, and blood samples were collected. MYBPC3-A31P was genotyped by DNA sequencing. Primers for LAMP with a LFD test were designed. The optimal conditions were determined, including temperature and time to completion for the reaction. The sensitivity of A31P-LAMP detection was compared between agarose gel electrophoresis (the standard method) and the LFD test. The A31P-LAMP-LFD test was randomly performed on seven cats (four with the A31P mutation and three wild-type cats).ResultsThe A31P-LAMP procedure was able to distinguish between cats with MYBPC3-A31P wild-type cats and MYBPC3-A31P mutant cats. The LAMP reactions were able to be completed in 60 min at a single temperature of 64◦C. Moreover, this study demonstrated that A31P-LAMP coupled with the LFD test allowed for A31P genotype detection at a lower DNA concentration than agarose gel electrophoresis.DiscussionsThis new A31P-LAMP with a LFD test is a successful and reliable assay with a rapid method, cost-effectiveness, and low requirements for sophisticated equipment for the detection of MYBPC3-A31P mutations. Thus, this assay has excellent potential and can be recognized as a novel screening test for hypertrophic cardiomyopathy associated with MYBPC3-A31P mutations in felines.

Altered Calcium Handling and Phosphorylation State are Associated With the Development of Hypertrophic Cardiomyopathy in a Murine Model of the Disease

Increased intracellular calcium ([Ca2+]i) is commonly associated with the development of hypertrophic cardiomyopathy (HCM). While some similarities exist, different HCM gene mutations lead to mutation-specific alterations in [Ca2+]i handling [1].

Importance of Vector Velocity Echocardiography and NT-proBNP in Identifying Individuals with Preclinical Hypertrophic Cardiomyopathy

Background and aim: Familial HCM gene mutation carriers without overt left ventricular hypertrophy (gene positive/phenotype negative G+/P-) can harbor subclinical changes in cardiovascular structure and function that precede the development of Hypertrophic Cardiomyopathy (HCM). Conventional echocardiography parameter ejection fraction is normal in HCM patients. We sought to investigate whether Velocity Vector Imaging (VVI) and NT-proBNP are more sensitive to evaluate heart function.

Preventative therapeutic approaches for hypertrophic cardiomyopathy.

Sarcomeric gene mutations are associated with the development of hypertrophic cardiomyopathy (HCM). Current drug therapeutics for HCM patients are effective in relieving symptoms, but do not prevent or reverse disease progression. Moreover, due to heterogeneity in the clinical manifestations of the disease, patients experience variable outcomes in response to therapeutics. Mechanistically, alterations in calcium handling, sarcomeric disorganization, energy metabolism and contractility participate in HCM disease progression. While some similarities exist, each mutation appears to lead to mutation‐specific pathophysiology. Furthermore, these alterations may precede or proceed development of the pathology. This review assesses the efficacy of HCM therapeutics from studies performed in animal models of HCM and human clinical trials. Evidence suggests that a preventative rather than corrective therapeutic approach may be more efficacious in the treatment of HCM. In addition, a clear understanding of mutation‐specific mechanisms may assist in informing the most effective therapeutic mode of action.

Studies of pharmacokinetics in beagle dogs and drug-drug interaction potential of a novel selective ZAK inhibitor 3h for hypertrophic cardiomyopathy treatment

Overexpression of leucine-zipper and sterile-α motif kinase (ZAK) in heart has been closely associated with the development of hypertrophic cardiomyopathy (HCM). N-(3-(1H-pyrazolo[3,4-b]pyridin-5-yl)ethynyl) benzene-sulfonamides, novel highly selective ZAK inhibitors, had exhibited reasonable orally therapeutic effects on HCM in spontaneous hypertensive rat models. In the present study, a rapid and sensitive HPLC-MS/MS method for determining ZAK inhibitor 3h in beagle dog plasma was developed and validated. Meanwhile, the pharmacokinetics in beagle dog and drug-drug interaction potential of 3h had been conducted. The pharmacokinetic results showed that the absolute oral bioavailability for 3h in beagle dogs was determined to be 61.9%, which was significantly higher than that in the previous determination in Spragur-Dawley rats (F = 20%). The Cytochrome P450 enzymes and P-glycoprotein mediated drug-drug interactions by 3h were also investigated using dog and human liver microsomes and Caco-2 cells. The results demonstrated that only CYP2C9 was obviously inhibited (IC50 = 1.66 μM). Besides, 3h could significantly decrease digoxin efflux ratio in Caco-2 experiments in a dose-dependent manner (IC50 = 13.3 μM). Considering 3h strongly suppressed the ZAK kinase activity with an IC50 of 3.3 nM, there are significantly differences between this IC50 value for ZAK inhibition and the present determinations of IC50 values. In general, the clinical drug-drug interaction potential for 3h could be well monitored during the treatment of HCM.

Low Molecular Mass Myocardial Hyaluronan in Human Hypertrophic Cardiomyopathy.

During the development of hypertrophic cardiomyopathy, the heart returns to fetal energy metabolism where cells utilize more glucose instead of fatty acids as a source of energy. Metabolism of glucose can increase synthesis of the extracellular glycosaminoglycan hyaluronan, which has been shown to be involved in the development of cardiac hypertrophy and fibrosis. The aim of this study was to investigate hyaluronan metabolism in cardiac tissue from patients with hypertrophic cardiomyopathy in relation to cardiac growth. NMR and qRT-PCR analysis of human cardiac tissue from hypertrophic cardiomyopathy patients and healthy control hearts showed dysregulated glucose and hyaluronan metabolism in the patients. Gas phase electrophoresis revealed a higher amount of low molecular mass hyaluronan and larger cardiomyocytes in cardiac tissue from patients with hypertrophic cardiomyopathy. Histochemistry showed high concentrations of hyaluronan around individual cardiomyocytes in hearts from hypertrophic cardiomyopathy patients. Experimentally, we could also observe accumulation of low molecular mass hyaluronan in cardiac hypertrophy in a rat model. In conclusion, the development of hypertrophic cardiomyopathy with increased glucose metabolism affected both hyaluronan molecular mass and amount. The process of regulating cardiomyocyte size seems to involve fragmentation of hyaluronan.

Formin Homology 2 Domain Containing 3 (FHOD3) Is a Genetic Basis for Hypertrophic Cardiomyopathy

BackgroundThe genetic cause of hypertrophic cardiomyopathy remains unexplained in a substantial proportion of cases. Formin homology 2 domain containing 3 (FHOD3) may have a role in the pathogenesis of cardiac hypertrophy but has not been implicated in hypertrophic cardiomyopathy. ObjectivesThis study sought to investigate the relation between FHOD3 mutations and the development of hypertrophic cardiomyopathy. MethodsFHOD3 was sequenced by massive parallel sequencing in 3,189 hypertrophic cardiomyopathy unrelated probands and 2,777 patients with no evidence of cardiomyopathy (disease control subjects). The authors evaluated protein-altering candidate variants in FHOD3 for cosegregation, clinical characteristics, and outcomes. ResultsThe authors identified 94 candidate variants in 132 probands. The variants’ frequencies were significantly higher in patients with hypertrophic cardiomyopathy (74 of 3,189 [2.32%]) than in disease control subjects (18 of 2,777 [0.65%]; p < 0.001) or in the gnomAD database (1,049 of 138,606 [0.76%]; p < 0.001). FHOD3 mutations cosegregated with hypertrophic cardiomyopathy in 17 families, with a combined logarithm of the odds score of 7.92, indicative of very strong segregation. One-half of the disease-causing variants were clustered in a small conserved coiled-coil domain (amino acids 622 to 655); odds ratio for hypertrophic cardiomyopathy was 21.8 versus disease control subjects (95% confidence interval: 1.3 to 37.9; p < 0.001) and 14.1 against gnomAD (95% confidence interval: 6.9 to 28.7; p < 0.001). Hypertrophic cardiomyopathy patients carrying (likely) pathogenic mutations in FHOD3 (n = 70) were diagnosed after age 30 years (mean 46.1 ± 18.7 years), and two-thirds (66%) were males. Of the patients, 82% had asymmetric septal hypertrophy (mean 18.8 ± 5 mm); left ventricular ejection fraction <50% was present in 14% and hypertrabeculation in 16%. Events were rare before age 30 years, with an annual cardiovascular death incidence of 1% during follow-up. ConclusionsFHOD3 is a novel disease gene in hypertrophic cardiomyopathy, accounting for approximately 1% to 2% of cases. The phenotype and the rate of cardiovascular events are similar to those reported in unselected cohorts. The FHOD3 gene should be routinely included in hypertrophic cardiomyopathy genetic testing panels.

МОРФОМЕТРИЧНІ ОСОБЛИВОСТІ СТІНОК ШЛУНОЧКІВ ТА МІЖШЛУНОЧКОВОЇ ПЕРЕГОРОДКИ СЕРЦЯ ЩУРІВ У НОРМІ ТА ПІСЛЯ ВНУТРІШНЬОПЛІДНОЇ ДІЇ АНТИГЕНУ

Recently diseases of cardiovascular system in children take one of the first places in Ukraine.The aim of the study – studying the morphometric features of walls and interventricular septum thickness of rat’s heart in normal conditions and after antenatal antigen impact.Materials and Methods. 144 hearts of laboratory rats were investigated. They were divided into 3 groups: I group – intact rats, ІІ – control group, that get intrauterine injection of Sodium Chloride solution 0.9 % 0.05 ml on the 18th day of antenatal development. III – the experimental group of rats, who were injected by 0.05 ml of anatoxin in a similar method. Serial sections were stained with hematoxylin and eosin.Results and Discussion. In the experimental group in newborn animals the indices of the thickness of right ventricle, left ventricle and interventricular septum are much lower than in the control. This tendency is observed until the 21st day, and on the 45th day all thickness indicators were significantly higher in experimental animals. Obtained results can be related with changes in the ratio of muscle and connective tissues by reducing of the first and increasing of the second. Wall’s thickening in experimental animals on the 45th day can be considered as a development of hypertrophic cardiomyopathy, which is one of the manifestations of UCTD in the heart.Conclusions. Intrauterine antenatal administration of the antigen may cause a disturbance in the formation of the connective tissue of the heart, which in the future may lead to decreasing of the adaptive capacity of the myocardium.

Classifying Cardiac Actin Mutations Associated With Hypertrophic Cardiomyopathy.

Mutations in the cardiac actin gene (ACTC1) are associated with the development of hypertrophic cardiomyopathy (HCM). To date, 12 different ACTC1 mutations have been discovered in patients with HCM. Given the high degree of sequence conservation of actin proteins and the range of protein–protein interactions actin participates in, mutations in cardiac actin leading to HCM are particularly interesting. Here, we suggest the classification of ACTC1 mutations based on the location of the resulting amino acid change in actin into three main groups: (1) those affecting only the binding site of the myosin molecular motor, termed M-class mutations, (2) those affecting only the binding site of the tropomyosin (Tm) regulatory protein, designated T-class mutations, and (3) those affecting both the myosin- and Tm-binding sites, called MT-class mutations. To understand the precise pathogenesis of cardiac actin mutations and develop treatments specific to the molecular cause of disease, we need to integrate rapidly growing structural information with studies of regulated actomyosin systems.

The Role of Extracellular Matrix Stiffness on Regulation of Cardiac Metabolic Activity: Implications for the Development of Hypertrophic Cardiomyopathy

The Role of Extracellular Matrix Stiffness on Regulation of Cardiac Metabolic Activity: Implications for the Development of Hypertrophic Cardiomyopathy

THE NEW GENOME VARIANTS IN RUSSIAN CHILDREN WITH GENETICALLY DETERMINED CARDIOMYOPATHIES REVEALED WITH MASSIVE PARALLEL SEQUENCING

Background: Cardiomyopathies in children are serious, continuously progressing myocardium diseases which are characterized by a variety of the causes, symptoms, implications, and high lethality. More than 400 genes that can cause hereditary heart and vessels diseases are described in scientific literature. The application of a high-performance method of massive parallel sequencing allows to conduct the investigation of genome extended targeted areas revealing the variants and analyzing them (bioinformatics) for pathogenicity.Aims: Identification of a genetic etiology of hereditary cardiomyopathies development in children’s population of the Russian Federation.Materials and methods: The research included 103 patients with various phenotypes of cardiomyopathies aged from 3 months up to 17 years 9 months who at the moment of examination were observed in the cardiology department and the department of recovery treatment with cardiovascular diseases in the NMRCCH. All patients were performed massive parallel sequencing analyzing the targeted areas of 404 genes which mutations lead to the development of heart and vessels hereditary diseases.Results: The diagnostic algorithm based on the method of a massive parallel sequencing was developed. 176 258 minor options were identified in the explored target areas of genome of 103 patients. An average number of the revealed nucleotide replacements different from the reference sequence was 1711. We observed that about 40% of all variants founded by our means were found in MYH7, MYBPC3, TTN, MYH6, SCN5A, DSC2 and TPM1 genes. Bioinformatics analysis allowed revealing 68 novel genome variants associated with cardiomyopathy development. The reliable association of carriage of pathogenic option in MYBPC3 gene with development of hypertrophic cardiomyopathy in the Russian children was found.Conclusions: The application of the offered algorithm allowed establishing laboratory diagnoses to 99 (96.1%) patients out from 103 investigated subjects including the syndromal and non-syndromal forms of heart and vessels hereditary diseases which showed a cardiomyopathy phenotype.

Perspectivas moleculares en cardiopatía hipertrófica: abordaje epigenético desde la modificación de la cromatina

Epigenetic alterations induced by environmental factors are more relevant each day for cardiovascular diseases. One of the most observed molecular components in hypertrophic cardiomyopathy is the reactivation of fetal genes caused by multiple conditions, including obesity, high blood pressure, aortic valve stenosis and congenital causes. Despite several investigations with the objective of obtaining information regarding molecular components of this condition, its influence in therapeutic strategies is relatively scarce.Nowadays information is being searched about proteins that modify the expression of the fetal genes that reactivate with this condition. The relationship between histones and DNA has a recognised control in the expression of genes that are subject to the environment and induce epigenetic alterations. Histone deacetylases are a group of proteins that have revealed to play an important role in differentiation the cardiac cell and could be clear components in the development of hypertrophic cardiomyopathy. In this study current knowledge about the influence of these proteins and possible therapeutic plans for hypertrophic cardiomyopathy are revised.

A Missense Mutation in the Obscurin Gene Leads to Hypertrophic Cardiomyopathy due to Deregulated Calcium Cycling

Obscurins are cytoskeletal proteins composed of adhesion and signaling motifs. Genomic linkage analysis has identified a missense mutation (R4344Q) in immunoglobulin domain 58 (Ig58) that is causally linked to the development of hypertrophic cardiomyopathy (HCM) in humans. To examine how R4344Q leads to HCM, we generated a knock-in mouse model that contains full-length obscurins carrying the R4344Q mutation. Mutant obscurins are readily expressed in cardiac muscles, and properly incorporated into sarcomeres. While sarcomeric assembly and organization are unaltered in 1-year old homozygous knock-in hearts, the expression levels of the Ca2+-handling protein SERCA2 are significantly increased. Consistent with this, homozygous knock-in cardiomyocytes exhibit increased rate of Ca2+-uptake and faster contractile kinetics. Exposure of ∼2-months old knock-in mice to mechanical stress via trans-aortic constriction (TAC) leads to severe cardiac hypertrophy within 4-8 weeks. Contractility and Ca2+-transients are significantly slower in knock-in cardiomyocytes subjected to TAC, which is in agreement with the reduced expression levels of key Ca2+-handling proteins, including RyR2 and SERCA2. Moreover, both RyR2 and SERCA2 exhibit decreased phosphorylation levels in knock-in TAC hearts, further indicating their altered functional properties. Structural analysis of wild type and mutant Ig58 revealed that the R4344Q mutation abolishes the formation of salt bridges between R4344 and E4360, resulting in altered distribution of the electrostatic charge over the Ig58 surface, and possibly interfering with binding of obscurins to other proteins. Consistent with this, obscurins are in a complex with the Ca2+-cycling protein phospholamban mediated by Ig58. Importantly, Ig58 containing the R4344Q mutation shows increased binding to phospholamban compared to wild type Ig58. In summary, our studies provide the first in vivo model to examine the molecular defects underlying HCM due to mutant obscurins, pointing towards a role in Ca2+ regulation.

GW26-e4567 The role of Hippo signal transduction pathway in the development of hypertrophic cardiomyopathy

GW26-e4567 The role of Hippo signal transduction pathway in the development of hypertrophic cardiomyopathy

Abstract 35: Pseudo-knockin Mice Expressing JPH2-A399S Develop Cardiac Hypertrophy by Magnetic Resonance Imaging

Background: Dysfunctional intracellular Ca2+ handling has been implicated in adverse cardiac remodeling leading to hypertrophy and failure. Recent evidence has linked mutations in the Ca2+ handling protein Junctophilin-2 (JPH2) with the development of hypertrophic cardiomyopathy (HCM). However, the mechanism remains unknown. Objective: To use advanced in vivo imaging modalities in conjunction with biochemical techniques to determine the mechanism of hypertrophic remodeling in a murine model hosting a novel JPH2 mutation. Methods and Results: 1. Pseudo-knockin (PKI) Mice: transgenic mice with the JPH2-A399S mutation (or WT JPH2) containing inducible shJPH2 were dosed with tamoxifen to knock down the combined levels of JPH2 to near WT expression. 2. MRI: A399S and WT PKI controls were imaged at 2 months post injection at which time body weight was similar for mutants (29.8±.81g) and controls (31.8±1.29g). Intragate (Bruker) was used to obtain FLASH cine images and EKG-gated tagged images were obtained to determine strain. MRI post-processing and measurements were performed using Amira and Diagnosoft software. A399S PKI mice exhibited significantly increased left ventricular mass (2.96±.21g/kg; n=4) compared to controls (2.27±.08g/kg; n=3) and max diastolic septal thickness (1.39±.05mm; n=9 versus 0.97±.00mm; n=4; P&lt;0.01). Mutants trended toward decreased septal strain (-8.97±1.04; n=4) compared to the control (-10.28; n=1) indicative of reduced regional contractility 3. Biochemistry: stress markers were measured by qPCR. Average BNP was increased over 3 fold. Larger sample size is needed to reach significance. Western blot showed no significant change (p=.78) in phosphorylated Ca2+/calmodulin-dependent protein kinase II, which is often activated by aberrant Ca2+ signaling. Conclusions: Our data show that the JPH2-A399S mutation leads to septal hypertrophy in PKI mice. This suggests that defects in JPH2 are sufficient to induce pathological cardiac remodeling. Despite the role of JPH2 in Ca2+ handling, this form of hypertrophy does not appear to be mediated by traditional Ca2+ signaling. Further studies will focus on alternative Ca2+-dependent pathways to elucidate the molecular mechanisms of these hypertrophic changes.