PRKAG2 Mutation Research Articles

PRKAG2 syndrome, a rare hypertrophic cardiomyopathy: a Brazilian long-term follow-up with extracardiac disorders.

This study aimed to provide a long-term follow-up of PRKAG2 syndrome and describe the new phenotypic aspects of the condition. PRKAG2 syndrome is a rare autosomal-dominant glycogen storage disease characterized by cardiac hypertrophy, ventricular pre-excitation, and conduction system disease. Fatal arrhythmias occur frequently. A family cohort of 66 participants was recruited. Clinical and genetic analyses were performed. Median age of 36.97±17.28 years, with 69.9% being men. Nineteen subjects carried the deleterious variant p.K290I of the PRKAG2 gene. This group experienced many malignant events, including eight pacemaker implants, three sudden cardiac deaths, five aborted cardiac arrests, four strokes, four premature neonatal deaths, two spontaneous abortions, five forceps deliveries, and 12 cesarean procedures. Extracardiac involvement, such as in neurocognitive and psychiatric disorders, has been observed only in carriers of mutations. Palpitations, Syncope, atrial fibrillation, atrial flutter, sinus pauses, and bradycardia were strongly and significantly associated with major or severe adverse events (sudden cardiac death, aborted cardiac arrest, pacemaker use, stroke, and congestive heart failure). Early diagnosis and intervention through antiarrhythmic drugs, anticoagulation, pacemaker implantation, radiofrequency catheter ablation, and cesarean section surgery improved the symptoms and survival rates. Mutations carriers were advised to avoid pregnancy. This study identified that the p.K291I_PRKAG2 mutation is associated with poor prognosis, highlighting the need for early intervention. Further research may uncover the potential connections between intellectual disability, miscarriage, and neonatal death in individuals with this syndrome.

Intrafamilial Phenotypical Variability Linked to PRKAG2 Mutation-Family Case Report and Review of the Literature.

PRKAG2 syndrome (PS) is a rare, early-onset autosomal dominant phenocopy of sarcomeric hypertrophic cardiomyopathy (HCM), that mainly presents with ventricular pre-excitation, cardiac hypertrophy and progressive conduction system degeneration. Its natural course, treatment and prognosis are significantly different from sarcomeric HCM. The clinical phenotypes of PRKAG2 syndrome often overlap with HCM due to sarcomere protein mutations, causing this condition to be frequently misdiagnosed. The syndrome is caused by mutations in the gene encoding for the γ2 regulatory subunit (PRKAG2) of 5' Adenosine Monophosphate-Activated Protein Kinase (AMPK), an enzyme that modulates glucose uptake and glycolysis. PRKAG2 mutations (OMIM#602743) are responsible for structural changes of AMPK, leading to an impaired myocyte glucidic uptake, and finally causing storage cardiomyopathy. We describe the clinical and investigative findings in a family with several affected members (NM_016203.4:c.905G>A or p.(Arg302Gln), heterozygous), highlighting the various phenotypes even in the same family, and the utility of genetic testing in diagnosing PS. The particularity of this family case is represented by the fact that the index patient was diagnosed at age 16 with cardiac hypertrophy and ventricular pre-excitation while his mother, by age 42, only had Wolff-Parkinson-White syndrome, without left ventricle hypertrophy. Both the grandmother and the great-grandmother underwent pacemaker implantation at a young age because of conduction abnormalities. Making the distinction between PS and sarcomeric HCM is actionable, given the early-onset of the disease, the numerous life-threatening consequences and the high rate of conduction disorders. In patients who exhibit cardiac hypertrophy coexisting with ventricular pre-excitation, genetic screening for PRKAG2 mutations should be considered.

953 KEY ROLE OF GENETIC ANALYSIS IN A FAMILIAR CASE OF HYPERTROPHIC CARDIAC PHENOTYPE AND VENTRICULAR PREEXCITATION RELATED TO PRKAG2 GENE MUTATION

Abstract A 38-year-old male patient (A2) was referred to our ambulatory for paroxysmal atrial fibrillation in young age and ventricular preexcitation. Echocardiographic evaluation showed left ventricle hypertrophy (localized particularly at inter-ventricular septum (SIV) and normal LV ejection fraction. He also had a positive family history of hypertrophic cardiomyopathy since the latter was already diagnosed with the maternal grandmother (M0), the mother (M1) and the two brothers (A1 and A3). His father was apparently healthy (P1- consanguineous third degree of the mother M1). Specifically, the mother (M1) was suffering from non-obstructive hypertrophic cardiomyopathy, and tachy-brady (paroxysmal atrial flutter, sinus arrest) syndrome requiring pacemaker implantation. The firstborn (A1) was affected by paroxysmal atrial fibrillation, ventricular prexcitation and mild hypertrophy of the interventricular septum (SIV). The third child (A3) had a diagnosis of hypertrophic cardiomyopathy and a history of successfully ablation of a left postero-septal accessory pathway. A3 suffered also by paroxysmal typical atrial common flutter. Genetic analysis of the proband A2 confirmed a heterozygous pathological mutation of the PRKAG2 gene. Thus, genetic analysis was extended to the other two brothers A1 and A3 and the mother. We proposed to the all three brothers electrophysiological study in order to assess arrhythmic substrate and appropriate therapy (strict FUP, PM or ICD implantation). Mutation of the PRKAG2 gene is a rare disease, classified as non-lysosomal cardiac glycogenosis with clinical onset in late adolescence or in the third decade of life and presents an autosomal dominant inheritance with complete penetrance. It is associated with cardiac arrhythmias, such as ventricular preexcitation (Wolff-Parkinson-White syndrome), sinus node disease, atrioventricular block, atrial fibrillation. Genetic analysis has a crucial role especially in the evaluation of inheritance with autosomal dominant transmission and regarding the prognostic impact, since PRKAG2 gene mutation involved a greater arrhythmic risk comparing with other subtypes of hypertrophic cardiomyopathy. Affected patients should be closely monitored to facilitate early detection of arrhythmia and conduction problems. PRKAG2 mutation should be considered in patients with LVH who develop AF or require permanent pacemakers at a young age. Early recognition is important to allow prompt identification and appropriate management of genetic carriers.

Abstract 15095: A Rare Cardiomyopathy Caught Offsides: Discovery of a New Phenotype

A 51-year-old male with Wolff-Parkinson-White (WPW) syndrome, atrial flutter, and third-degree heart block necessitating pacemaker placement presented with asymptomatic atrial flutter. The patient’s father and paternal aunt were diagnosed with WPW and died suddenly at approximate ages of 40 and 60 years, respectively. An echocardiogram showed RV dilation and moderate to severe RV systolic dysfunction with normal LV ejection fraction. Cardiac CT demonstrated thinning of the RV free wall and free wall outpouchings during systole (Figure), as well as moderate asymmetric LV hypertrophy, aneurysmal changes of the basal inferior wall, and dyskinesis of the LV apex. At this time, the differential for RV dysfunction included group 1 pulmonary hypertension, ischemic cardiomyopathy, sarcoidosis, and arrhythmogenic right ventricular cardiomyopathy (ARVC). Subsequent testing excluded all diagnoses other than ARVC. Additionally, 2010 Task Force Criteria for ARVC were not met. However, genetic testing revealed p.Arg302Gln mutation in the PRKAG2 gene. AMP-activated protein kinase (AMPK) is a highly conserved kinase encoded by the PRKAG2 gene that is responsible for controlling cellular energy homeostasis. This PRKAG2 mutation, within the spectrum of genetic mutations resulting in the rare autosomal dominant PRKAG2 syndrome, is characterized by glycogen storage cardiomyopathy and a familial form of WPW, supraventricular arrhythmias, and left ventricular hypertrophy. To the best of our knowledge, this is the first report of PRKAG2 syndrome with prominent abnormalities of the RV, and it expands the scope of PRKAG2 syndrome. Management included implantation of an AICD and ongoing careful monitoring for arrhythmia and heart failure. The patient’s siblings and children were referred for genetic counseling. This case highlights the importance of a broad differential diagnosis and exhaustive evaluation of patients presenting with right ventricular abnormalities.

Left ventricular non-compaction cardiomyopathy associated with the PRKAG2 mutation

Left ventricular non-compaction cardiomyopathy (LVNC) is one of the most common inherited cardiovascular diseases. The genetic backgrounds of most LVNC patients are not fully understood. We collected clinical data, family histories, and blood samples and performed genetic analysis using next-generation sequencing (NGS) from a Chinese family of 15 subjects. Clinically LVNC affected subjects showed marked cardiac phenotype heterogeneity. We found that these subjects with LVNC carried a missense heterozygous genetic mutation c.905G>A (p.R302Q) in γ2 subunit of AMP-activated protein kinase (PRKAG2) gene through NGS. Individuals without this mutation showed no symptoms or cardiac structural abnormalities related to LVNC. One subject was the victim of sudden cardiac death. To sum up, PRKAG2 mutation c.905G>A (p.R302Q) caused familial LVNC. Our results described a potentially pathogenic mutation associated with LVNC, which may further extend the spectrum of LVNC phenotypes related to PRKAG2 gene mutations.

AKT-mTOR signaling-mediated rescue of PRKAG2 R302Q mutant-induced familial hypertrophic cardiomyopathy by treatment with β-adrenergic receptor (β-AR) blocker metoprolol.

Protein kinase AMP-activated non-catalytic subunit gamma 2 gene (PRKAG2) cardiac syndrome, caused by mutations in PRKAG2, often shows myocardial hypertrophy and abnormal glycogen deposition in cardiomyocytes. However, it remains incurable due to a lack of a management guideline for treatment. We constructed a fluorescently labeled adenovirus carrying the wild-type or R302Q mutant of the PRKAG2 gene, infected neonatal rat cardiomyocytes (NRCMs) and H9C2 cell lines, and then analyzed changes in AMP-activated protein kinase (AMPK) activity, cell hypertrophy, glycogen storage, and cell proliferation when presence or absence of metoprolol or protein kinase A (PKA) inhibition H89, and then analyzed the changes in AKT-mTOR signal transduction activity. Overexpression of PRKAG2 R302Q in primary cardiomyocytes increased the activity of AMPK, induced cellular hypertrophy and glycogen storage, and promoted the phosphorylation levels of AKT-mTOR signaling pathway. Application of either β1-adrenergic receptor (β1-AR) blocker metoprolol or PKA inhibitor H89 to the cardiomyocytes rescued the hypertrophic cardiomyopathy (HCM)-like phenotypes induced by PRKAG2 R302Q, including suppression of both AKT-mTOR phosphorylation and AMPK activity. The current study not only determined the mechanism regulating HCM induced by PRKAG2 R302Q mutant, but also demonstrated a therapeutic strategy using β1-AR blocker to treat the patients with PRKAG2 cardiac syndrome.

Generation of two iPSC lines from hypertrophic cardiomyopathy patients carrying MYBPC3 and PRKAG2 variants

Hypertrophic cardiomyopathy (HCM) is an inherited cardiac disorder characterized by a thick left ventricular wall and an increased risk of arrhythmias, heart failure, and sudden cardiac death. The MYBPC3 and PRAKG2 are known causal genes for HCM. Here we generated two human-induced pluripotent stem cell lines from two HCM patients carrying two heterozygous mutations in MYBPC3 (c.459delC) and PRKAG2 (c.1703C > T). Both iPSC lines expressed pluripotent markers, had a normal karyotype, and were able to differentiate into three germ layers, making them potentially valuable tools for modeling HCM in vitro and investigating the pathological mechanisms related to these two variants.

DEVELOPMENT OF AN IN VITRO STUDY MODEL OF PRKAG2 CARDIOMYOPATHY USING HUMAN INDUCED PLURIPOTENT STEM CELLS

<h3>Background</h3> PRKAG2 cardiomyopathy is an autosomal dominant syndrome due to mutation in PRKAG2 gene, which encodes the γ2 subunit of the adenosine monophosphate (AMP)-activated protein kinase (AMPK). PRKAG2 syndrome leads to intracellular cardiomyocyte glycogen storage dysfunctions and clinical conditions that overlap hypertrophic cardiomyopathy, hampering its correct diagnosis. Our group identified a patient with a novel heterozygous missense mutation in PRKAG2 gene (c.1203C>A, p.His401Gln), with a malignant disease phenotype characterized by severe cardiac hypertrophy and cases of sudden death in young relatives. In this regard, induced pluripotent stem cells (iPSC) preserve the donor genome and can be differentiated into specialized cell types, being particularly interesting to study diseases that affect tissues which are difficult to access. Thus, this work aims to establish an in vitro study model of PRKAG2 cardiomyopathy through generation of human iPSC and its subsequent differentiation into patient-specific cardiomyocytes. <h3>Methods</h3> iPSC from patient with PRKAG2 mutation and from a health relative were generated from erythroblasts using CytoTune™-iPSC 2.0 Sendai Reprogramming Kit (containing OCT3/4, KLF4, SOX2 and cMYC as reprogramming factors) and their karyotype was analyzed by qPCR using hPSC Genetic Analysis Kit (Stemcell Technologies). The iPSC strains obtained were differentiated into cardiomyocytes by inducing mesoderma formation with glycogen synthase kinase inhibitor 3-β, CHIR99021 (5 µM), on day 0 and cardiogenic mesoderma formation with the Wnt inhibitor, Wnt-C59 (2 µM), on day 2. On day 30 of culture, cells were stained with periodic acid-Schiff (PAS) to assess cytosolic glycogen storage. <h3>Results</h3> Both iPSC strains have embryonic-like phenotype and normal karyotype. Moreover, preliminary differentiation studies suggest glycogen accumulation in cardiomyocytes derived from the iPSC strain with PRKAG2 mutation. Evaluation of pluripotency factors expression and the ability to differentiate in the 3 embryonic germinative layers are ongoing in iPSC strains. <h3>Conclusion</h3> At the end of the characterization of the generated iPSC and of iPSC-derived cardiomyocytes, is expected that this approach will make possible the establishment of an in vitro study platform to reveal molecular mechanisms triggered by the c.1203C>A mutation that may contribute to the development of new therapies and prognostic evaluation of patients with PRKAG2 syndrome.

Clinical characteristics and natural history of PRKAG2 syndrome

Abstract Purpose Mutations in the PRKAG2 gene cause a syndrome characterized by hypertrophic cardiomyopathy, conduction disease and ventricular preexcitation. Only a small number of cases have been reported, and the natural history of the disease is poorly understood. The aim of this study is to describe phenotype and natural history of PRKAG2 mutation in a large multicenter international cohort. Methods We retrospectively studied clinical, electrocardiographic and echocardiographic data from 90 individuals with PRKAG2 mutations (53% males, 33±21 years) from 27 centers. Results At baseline evaluation, 93% of patients were in NYHA functional class I-II. Maximum left ventricular (LV) wall thickness was 18±8 mm and LV hypertrophy (LVH) was present in 60 (67%) subjects at baseline. LV ejection fraction was 61±12%. Seventeen pactients (19%) had a pacemaker (mean age at implantation 37±15and 16 (18%) had atrial fibrillation (AF) (mean age 41±23 years) and 33% had ventricular preexcitation or had undergone an accessory pathway ablation. After a median follow-up of 6 years (IQR:2.3–13.9), 71% of individuals had LVH, 29% had AF, 21% a de novo pacemaker (mean age at implantation 38±18 years), 14% required admission for heart failure (HF), 8% experienced sudden cardiac death or equivalent, 4% required a heart transplant and 13% died. Conclusions PRKAG2 syndrome is a severe, progressive cardiomyopathy characterized by high rates of AF, conduction disease, advanced HF and life-threatening arrhythmias. Outcome is not clearly related to the classical features of preexcitation and severe LVH, which are not always present. Natural history of PRKAG2 syndrome Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): Instituto de Salud Carlos III (ISCIII)

Wolff-Parkinson-White syndrome: De novo variants and evidence for mutational burden in genes associated with atrial fibrillation.

Wolff-Parkinson-White (WPW) syndrome is a relatively common arrhythmia affecting ~1-3/1,000 individuals. Mutations in PRKAG2 have been described in rare patients in association with cardiomyopathy. However, the genetic basis of WPW in individuals with a structurally normal heart remains poorly understood. Sudden death due to atrial fibrillation (AF) can also occur in these individuals. Several studies have indicated that despite ablation of an accessory pathway, the risk of AF remains high in patients compared to general population. We applied exome sequencing in 305 subjects, including 65 trios, 80 singletons, and 6 multiple affected families. We used de novo analysis, candidate gene approach, and burden testing to explore the genetic contributions to WPW. A heterozygous deleterious variant in PRKAG2 was identified in one subject, accounting for 0.6% (1/151) of the genetic basis of WPW in this study. Another individual with WPW and left ventricular hypertrophy carried a known pathogenic variant in MYH7. We found rare de novo variants in genes associated with arrhythmia and cardiomyopathy (ANK2, NEBL, PITX2, and PRDM16) in this cohort. There was an increased burden of rare deleterious variants (MAF ≤ 0.005) with CADD score ≥ 25 in genes linked to AF in cases compared to controls (P = .0023). Our findings show an increased burden of rare deleterious variants in genes linked to AF in WPW syndrome, suggesting that genetic factors that determine the development of accessory pathways may be linked to an increased susceptibility of atrial muscle to AF in a subset of patients.

Isolated glycogen storage disease of the heart

Isolated glycogen storage disease of the heart (PRKAG2 syndrome) is a form of glycogenosis, which is characterized by left ventricular hypertrophy, similar to the phenotype of hypertrophic cardiomyopathy, associated with pre-excitation of the ventricles and conduction disorders. The disease is caused by mutations in the gene PRKAG2 encoding for the 5’Adenosine Monophosphate-Activated Protein Kinase (AMPK), specifically for its y2 regulatory subunit, inheritance — autosomal dominant. A review of the literature data and clinical observation of two patients from the same family with the mutation c905C>A (p.Arg302Gln) in the PRKAG2 gene associated with WPW syndrome and early development of conduction disorders requiring implantation of a pacemaker are presented. The issues of diagnosis and treatment strategy of the disease were discussed.

Patient with a PRKAG2 mutation who developed Immunoglobulin A nephropathy: a case report.

Background PRKAG2 syndrome (PS) is a rare, early-onset autosomal dominant inherited disease caused by mutations in PRKAG2, the gene encoding the regulatory γ2 subunit of adenosine monophosphate-activated protein kinase. PRKAG2 syndrome is associated with many cardiac manifestations, including pre-excitation, arrhythmias, left ventricular hypertrophy, and chronotropic incompetence frequently leading to early pacemaker placement. A meta-analysis of genome-wide association data in subjects with chronic kidney disease (CKD) identified a susceptibility locus in an intron of PRKAG2, which has been replicated in other studies. However, CKD has not been reported in patients with PS or mutations in PRKAG2.Case summaryWe report a case of a woman diagnosed at age 27 with PS when she presented with atrial fibrillation and pre-excitation on electrocardiogram. By age 35, she had developed mild renal insufficiency and a biopsy demonstrated IgA nephropathy (IGAN).DiscussionThis is the first reported case of IGAN in a patient with PS. We discuss both PS and IGAN and the potential mechanisms by which they could be related.

K475E PRKAG2 Mutation: Cardiac Phenotype and Targeted Therapy Using Rapamycin

BackgroundWe identified a novel mutation (K475E) in PRKAG2, coding for protein kinase AMP‐activated non‐catalytic subunit γ2, during a 27‐week prenatal ultrasound. A hypertrophic cardiomyopathy (HCM) phenotype was later confirmed. We have demonstrated in vitro that the K475E mutation led to increases in cardiomyocytes size and area which can be reversed by rapamycin. We have developed transgenic mouse lines with cardiac‐specific expression of the human wild type (TgWT) or K475E mutant (TgK475E) PRKAG2. The TgK475E mice exhibit many human PRKAG2 HCM phenotypes, including cardiac hypertrophy, glycogen overload and sudden death.ObjectiveTo characterize K475E‐induced cardiac phenotype in vivo and develop a targeted therapy using mTOR inhibition strategy for PRKAG2 mutation‐induced HCM.MethodsCardiac hypertrophy was monitored and cardiac glycogen levels were measured at several developmental stages. Neonatal mice (2‐wk old) were treated daily with vehicle or rapamycin (2 mg/kg, ip) for 4 weeks. Cardiac function was monitored longitudinally by echocardiography.ResultsHypertrophy in TgK475E mice was confirmed. Histology revealed large vacuoles and high glycogen content in TgK475E myocytes throughout the ventricles. Echocardiography confirmed that LV mass dramatically increased in TgK475E mice starting from 5 weeks of age. Daily rapamycin treatment for 2 weeks dramatically decreased 1) cardiac hypertrophy and 2) glycogen overload in TgK475E mice. These beneficial effects of rapamycin were significantly tempered, however, when we switched to an alternative dosing regimen (one ip injection/3 days) of rapamycin.ConclusionThe new transgenic mouse model reflects the early onset phenotype of the K475E mutation‐induced HCM in humans. The mTOR signaling pathway is involved in K475E induced HCM. Moreover, the mTOR inhibition strategy as targeted therapy for PRKAG2 induced HCM is effective and should be studied further.Support or Funding InformationThis study was supported by NIH P30GM114750 and the Oh‐Zopfi Research Award, Women &amp; Infant's Hospital.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Genetic basis and outcome in a nationwide study of Finnish patients with hypertrophic cardiomyopathy.

AimsNationwide large‐scale genetic and outcome studies in cohorts with hypertrophic cardiomyopathy (HCM) have not been previously published.Methods and resultsWe sequenced 59 cardiomyopathy‐associated genes in 382 unrelated Finnish patients with HCM and found 24 pathogenic or likely pathogenic mutations in six genes in 38.2% of patients. Most mutations were located in sarcomere genes (MYBPC3, MYH7, TPM1, and MYL2). Previously reported mutations by our study group (MYBPC3‐Gln1061Ter, MYH7‐Arg1053Gln, and TPM1‐Asp175Asn) and a fourth major mutation MYH7‐Val606Met accounted for 28.0% of cases. Mutations in GLA and PRKAG2 were found in three patients. Furthermore, we found 49 variants of unknown significance in 31 genes in 20.4% of cases. During a 6.7 ± 4.2 year follow‐up, annual all‐cause mortality in 482 index patients and their relatives with HCM was higher than that in the matched Finnish population (1.70 vs. 0.87%; P < 0.001). Sudden cardiac deaths were rare (n = 8). Systolic heart failure (hazard ratio 17.256, 95% confidence interval 3.266–91.170, P = 0.001) and maximal left ventricular wall thickness (hazard ratio 1.223, 95% confidence interval 1.098–1.363, P < 0.001) were independent predictors of HCM‐related mortality and life‐threatening cardiac events. The patients with a pathogenic or likely pathogenic mutation underwent an implantable cardioverter defibrillator implantation more often than patients without a pathogenic or likely pathogenic mutation (12.9 vs. 3.5%, P < 0.001), but there was no difference in all‐cause or HCM‐related mortality between the two groups. Mortality due to HCM during 10 year follow‐up among the 5.2 million population of Finland was studied from death certificates of the National Registry, showing 269 HCM‐related deaths, of which 32% were sudden.ConclusionsWe identified pathogenic and likely pathogenic mutations in 38% of Finnish patients with HCM. Four major sarcomere mutations accounted for 28% of HCM cases, whereas HCM‐related mutations in non‐sarcomeric genes were rare. Mortality in patients with HCM exceeded that of the general population. Finally, among 5.2 million Finns, there were at least 27 HCM‐related deaths annually.

A Novel PRKAG2 Mutation (K475E): Early‐Onset Cardiac Phenotype and Targeted Therapy

BackgroundMutations in PRKAG2 have been implicated in hypertrophic cardiomyopathy (HCM). We identified a novel PRKAG2 mutation, K475E, in a neonate with prenatal onset of HCM noted on a 27‐week prenatal ultrasound. We have demonstrated in vitro that K475E mutation led to increases in cardiomyocytes size and area which can be reversed by rapamycin.ObjectiveTo characterize K475E‐induced cardiac phenotype in vivo, we developed two new transgenic mouse lines with cardiac‐specific expression of the human wild type (TgWT) or K475E mutant (TgK475E) PRKAG2. The goal of this study was to explore the effectiveness of rapamycin for targeted therapy for PRKAG2 mutation‐induced HCM.MethodsHuman WT and K475E DNA constructs were inserted into a pBluescript vector with the mouse α‐myosin heavy chain promoter. Transgenic mice were established by pronucleus microinjection. Rapamycin was treated from two‐week to six‐aged mice. Cardiac hypertrophy was examined and cardiac function changes were monitored by echocardiography.ResultsHypertrophy in TgK475E mice was confirmed by their significant increases in heart weight/body weight and heart weight/tibial length ratios versus the non‐transgenic control and TgWT mice. Histology revealed large vacuoles and high glycogen content in TgK475E myocytes throughout the ventricles. Echocardiography confirmed that LV mass dramatically increased in TgK475E mice starting from 5 weeks of age. Rapamycin treatment dramatically decreased 1) the ratios of heart weight/body weight and heart weight/tibia length and 2) glycogen overload in TgK475E mice. Moreover, K475E mutation caused inhibition of AMPK which was rectified by rapamycin treatment.ConclusionThese results indicate the transgenic mouse model reflects the early onset phenotype of the K475E mutation‐induced HCM. The mTOR signaling pathway is involved in K475E induced HCM. Our study suggests that mTOR inhibition strategy as targeted therapy for PRKAG2 induced HCM is effective and should be studied further.Support or Funding Information1. NIH P30GM114750 2. Oh‐Zopfi Research Award, Women &amp; Infant's Hospital, RI.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Human γ2-AMPK Mutations.

In humans, dominant mutations in the gene encoding the regulatory γ2-subunit of AMP-activated protein kinase (PRKAG2) result in a highly penetrant phenotype dominated by cardiac features: left ventricular hypertrophy, ventricular pre-excitation, atrial tachyarrhythmia, cardiac conduction disease, and myocardial glycogen storage. The discovery of a link between the cell's fundamental energy sensor, AMPK, and inherited cardiac disease catalyzed intense interest into the biological role of AMPK in the heart. In this chapter, we provide an introduction to the spectrum of human disease resulting from pathogenic variants in PRKAG2, outlining its discovery, clinical genetics, and current perspectives on its pathogenesis and highlighting mechanistic insights derived through the evaluation of disease models. We also present a clinical perspective on the major components of the cardiomyopathy associated with mutations in PRKAG2, together with less commonly described extracardiac features, its prognosis, and principles of management.

Molecular Pathogenesis of Familial Wolff-Parkinson-White Syndrome.

Familial Wolff-Parkinson-White (WPW) syndrome is an autosomal dominant inherited disease and consists of a small percentage of WPW syndrome which exhibits ventricular pre-excitation by development of accessory atrioventricular pathway. A series of mutations in PRKAG2 gene encoding gamma2 subunit of 5'AMP-activated protein kinase (AMPK) has been identified as the cause of familial WPW syndrome. AMPK is one of the most important metabolic regulators of carbohydrates and lipids in many types of tissues including cardiac and skeletal muscles. Patients and animals with the mutation in PRKAG2 gene exhibit aberrant atrioventricular conduction associated with cardiac glycogen overload. Recent studies have revealed "novel" significance of canonical pathways leading to glycogen synthesis and provided us profound insights into molecular mechanism of the regulation of glycogen metabolism by AMPK. This review focuses on the molecular basis of the pathogenesis of cardiac abnormality due to PRKAG2 mutation and will provide current overviews of the mechanism of glycogen regulation by AMPK. J. Med. Invest. 65:1-8, February, 2018.

CRISPR correction of the PRKAG2 gene mutation in the patient's induced pluripotent stem cell-derived cardiomyocytes eliminates electrophysiological and structural abnormalities

Mutations in the PRKAG2 gene encoding the γ-subunit of adenosine monophosphate kinase (AMPK) cause hypertrophic cardiomyopathy (HCM) and familial Wolff-Parkinson-White (WPW) syndrome. Patients carrying the R302Q mutation in PRKAG2 present with sinus bradycardia, escape rhythms, ventricular preexcitation, supraventricular tachycardia, and atrioventricular block. This mutation affects AMPK activity and increases glycogen storage in cardiomyocytes. The link between glycogen storage, WPW syndrome, HCM, and arrhythmias remains unknown. The purpose of this study was to investigate the pathological changes caused by the PRKAG2 mutation. We tested the hypothesis that patient's induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) display clinical aspects of the disease. Using clustered regularly interspaced short palindromic repeats (CRISPR) technology, we corrected the mutation and then generated isogenic iPSC-CMs. Action potentials were recorded from spontaneously firing and paced cardiomyocytes using the patch clamp technique. Using a microelectrode array setup, we recorded electrograms from iPSC-CMs clusters. Transmission electron microscopy was used to detect ultrastructural abnormalities in the mutated iPSC-CMs. PRKAG2-mutated iPSC-CMs exhibited abnormal firing patterns, delayed afterdepolarizations, triggered arrhythmias, and augmented beat rate variability. Importantly, CRISPRcorrection eliminated the electrophysiological abnormalities, the augmented glycogen, storage, and cardiomyocyte hypertrophy. PRKAG2-mutated iPSC-CMs displayed functional and structural abnormalities, which were abolished by correcting the mutation in the patient's iPSCs using CRISPR technology.

3880Correcting the PRKAG2 mutation in WPW patient's induced pluripotent stem cells using CRISPR/Cas9 eliminates arrhythmic firing patterns in the derived cardiomyocytes

3880Correcting the PRKAG2 mutation in WPW patient's induced pluripotent stem cells using CRISPR/Cas9 eliminates arrhythmic firing patterns in the derived cardiomyocytes

Wolff-Parkinson-White Syndrome with Ventricular Hypertrophy in a Brazilian Family.

Case seriesPatient: —Final Diagnosis: PRKAG2 syndromeSymptoms: Palpitation • dyspnea and fatigue • syncopeMedication: —Clinical Procedure: Radiofrequency catheter ablation • pacemaker implantion • antiarrhythmic drugsSpecialty: CardiologyObjective:Rare diseaseBackground:PRKAG2 syndrome diagnosis is already well-defined as Wolff-Parkinson-White syndrome (WPW), ventricular hypertrophy (VH) due to glycogen accumulation, and conduction system disease (CSD). Because of its rarity, there is a lack of literature focused on the treatment. The present study aimed to describe appropriate strategies for the treatment of affected family members with PRKAG2 syndrome with a long follow-up period.Case Report:We studied 60 selected individuals from 84 family members (32 males, 53.3%) (mean age 27±16 years). Patients with WPW and/or VH were placed in a group of 18 individuals, in which 11 (61.1%) had VH and WPW, 6 (33.3%) had isolated WPW, and 1 (5.6%) had isolated VH. Palpitations occurred in 16 patients (88.9%), chest pain in 11 (61.1%), dizziness in 13 (72.2%), syncope in 15 (83.3%), and dyspnea in 13 (72%). Sudden cardiac death (SCD) occurred in 2 (11.1%), and 2 patients with cardiac arrest (CA) had asystole and pre-excited atrial flutter-fibrillation (AFL and AF) as the documented mechanism. Transient ischemic attack (TIA) and learning/language disabilities with delayed development were observed. Genetic analysis identified a new missense pathogenic variant (p.K290I) in the PRKAG2 gene. Cardiac histopathology demonstrated the predominance of vacuoles containing glycogen derivative and fibrosis. The treatment was based on hypertension and diabetes mellitus (DM) control, antiarrhythmic drugs (AD), anticoagulation, and radiofrequency catheter ablation (RCA). Six patients (33.3%) underwent pacemaker implantation (PM).Conclusions:The present study describes the clinical treatment for a rare cardiac syndrome caused by a PRKAG2 mutation.