Abstract 215: The Role of Titin in Cardiac Function: Studies in Two Genetically Engineered Mouse Models With Disparate Titin’s Size

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Mei Methawasin ◽  
Kirk R Hutchinson ◽  
John E Smith ◽  
Henk L Granzier
Keyword(s):  
Mouse Model ◽  
Diastolic Dysfunction ◽  
Diastolic Function ◽  
Exercise Capacity ◽  
Mouse Models ◽  
Wheel Running ◽  
Left Ventricular ◽  
Genetically Engineered ◽  
Passive Stiffness ◽  
Genetically Engineered Mouse Models

Titin, a myofilament that acts as a molecular spring in the sarcomere, is considered the main contributor to passive stiffness of cardiomyocytes and is responsible for cardiac diastolic function. Increased titin stiffness is related to diastolic dysfunction and HFpEF (Heart Failure with preserved Ejection Fraction). Alteration in size of titin’s spring region leads to changes in cardiomyocyte and left ventricular (LV) chamber stiffness. We tested the effect of alteration in titin’s size in two genetically engineered mouse models. We investigated the effect of shortening titin’s spring region in a mouse model in which I-band/A-band region of titin’s spring has been deleted (TtnΔIAjxn ), in comparison to the effect of lengthening titin’s spring region in a mouse model deficient in titin splicing factor (Rbm20ΔRRM). Integrative approaches were used from single cardiomyocyte mechanics to pressure-volume analysis and exercise study. Study of skinned LV cardiomyocytes revealed that cellular passive stiffness was inversely related to the size of titin. Cellular passive stiffness was increased in TtnΔIAjxn homozygous (-/-) (~ 110 % higher than wildtype (WT)) and was reduced in a graded manner in Rbm20ΔRRM heterozygous (+/-) and -/- cardiomyocytes (~61% and ~87% less than WT). This effect was carried through at the LV chamber level which could be demonstrated in pressure volume (PV) analysis as an increased end-diastolic pressure-volume relationship (EDPVR) in TtnΔIAjxn -/- (~110% higher than WT’s hearts) and reduced EDPVR in Rbm20ΔRRM +/- and -/- (~57% and ~48% less than WT’s hearts). Free-wheel running studies revealed a running deficiency in TtnΔIAjxn -/- mice but an increase in exercise capacity in Rbm20ΔRRM +/– mice. Conclusions: Functional studies from the cellular to in-vivo LV chamber levels showed that mice with shortening of titin’s spring region had increased LV stiffness, diastolic dysfunction and reduced exercise capacity, while mice with lengthening titin’s spring region had compliant LV and increased exercise capacity. Thus, our work supports titin’s important roles in LV diastolic function and suggests that modification of the size of titin’s spring region could be a potential therapeutic strategy for HFpEF.

Abstract 76: Experimentally Increasing Titin’s Compliance in a Mouse Model of Heart Failure with Preserved Ejection Fraction Ameliorates Diastolic Dysfunction

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Mei Methawasin ◽  
Joshua G Strom ◽  
Rebecca E Slater ◽  
Vanessa Fernandez ◽  
Chandra Saripalli ◽  
...  
Keyword(s):  
Mouse Model ◽  
Diastolic Dysfunction ◽  
Transcriptional Control ◽  
Left Ventricular ◽  
Rna Recognition Motif ◽  
Rna Recognition ◽  
Preserved Ejection Fraction ◽  
Passive Stiffness ◽  
Recognition Motif ◽  
Transaortic Constriction

Increasing titin length in the heart through functional deletion of the RNA recognition motif (RRM) of RBM20 protein leads to a reduction of left ventricular (LV) chamber stiffness in sedentary mice. We tested the therapeutic effect of upregulating compliant titins by creating diastolic dysfunction in a mouse model with inducible RBM20 inhibition (MerCreMer;cRbm20ΔRRM). Under transcriptional control of an MHC6 promoter, RBM20 function of MerCreMer;cRbm20ΔRRM mice was inhibited in time- and cardiac-specific manners. Adult male MerCreMer;cRbm20ΔRRM mice had undergone transaortic constriction (TAC) surgery with Deoxycorticosterone acetate (DOCA) pellet implantation. Two weeks after TAC+DOCA surgery, mice developed LV hypertrophy and diastolic dysfunction as demonstrated by echocardiography. Four weeks after surgery, pressure volume analysis revealed that LV chamber stiffness was markedly increased in TAC+DOCA mice (140% increased versus sham). However, the TAC+DOCA mice with RBM20 inhibition developed less severe LV chamber stiffness (29% increased versus sham). Passive stiffness measurements showed a reduction of cardiomyocyte stiffness in TAC+DOCA mice with RBM20 inhibition. Inhibition of the RBM20-based splicing system results in expression of compliant mutant N2BA titin which consequently lead to reduction of cardiomyocyte stiffness and LV chamber stiffness in a mouse model with diastolic dysfunction.

scholarly journals Metformin improves diastolic function in an HFpEF-like mouse model by increasing titin compliance

2018 ◽  
Vol 151 (1) ◽  
pp. 42-52 ◽  
Author(s):  
Rebecca E. Slater ◽  
Joshua G. Strom ◽  
Mei Methawasin ◽  
Martin Liss ◽  
Michael Gotthardt ◽  
...  
Keyword(s):  
Ejection Fraction ◽  
Mouse Model ◽  
Diastolic Function ◽  
Left Ventricular ◽  
Muscle Stiffness ◽  
Exercise Intolerance ◽  
Diabetic Patients ◽  
Preserved Ejection Fraction ◽  
Passive Stiffness ◽  
Diastolic Stiffness

Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome characterized by a preserved ejection fraction but increased diastolic stiffness and abnormalities of filling. Although the prevalence of HFpEF is high and continues to rise, no effective therapies exist; however, the diabetic drug metformin has been associated with improved diastolic function in diabetic patients. Here we determine the therapeutic potential of metformin for improving diastolic function in a mouse model with HFpEF-like symptoms. We combine transverse aortic constriction (TAC) surgery with deoxycorticosterone acetate (DOCA) supplementation to obtain a mouse model with increased diastolic stiffness and exercise intolerance. Echocardiography and pressure–volume analysis reveal that providing metformin to TAC/DOCA mice improves diastolic function in the left ventricular (LV) chamber. Muscle mechanics show that metformin lowers passive stiffness of the LV wall muscle. Concomitant with this improvement in diastolic function, metformin-treated TAC/DOCA mice also demonstrate preserved exercise capacity. No metformin effects are seen in sham operated mice. Extraction experiments on skinned ventricular muscle strips show that the metformin-induced reduction of passive stiffness in TAC/DOCA mice is due to an increase in titin compliance. Using phospho-site-specific antibodies, we assay the phosphorylation of titin’s PEVK and N2B spring elements. Metformin-treated mice have unaltered PEVK phosphorylation but increased phosphorylation of PKA sites in the N2B element, a change which has previously been shown to lower titin’s stiffness. Consistent with this result, experiments with a mouse model deficient in the N2B element reveal that the beneficial effect of metformin on LV chamber and muscle stiffness requires the presence of the N2B element. We conclude that metformin offers therapeutic benefit during HFpEF by lowering titin-based passive stiffness.

scholarly journals A Mouse Model to Assess STAT3 and STAT5A/B Combined Inhibition in Health and Disease Conditions

Cancers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1226 ◽  
Author(s):  
Herwig P. Moll ◽  
Julian Mohrherr ◽  
Leander Blaas ◽  
Monica Musteanu ◽  
Patricia Stiedl ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Mouse Model ◽  
Mouse Models ◽  
Marked Reduction ◽  
Genetically Engineered ◽  
Tissue Specific ◽  
Genetically Engineered Mouse Models ◽  
Pharmacological Inhibition ◽  
Specific Manner ◽  
Health And Disease

Genetically-engineered mouse models (GEMMs) lacking diseased-associated gene(s) globally or in a tissue-specific manner represent an attractive tool with which to assess the efficacy and toxicity of targeted pharmacological inhibitors. Stat3 and Stat5a/b transcription factors have been implicated in several pathophysiological conditions, and pharmacological inhibition of both transcription factors has been proposed to treat certain diseases, such as malignancies. To model combined inhibition of Stat3 and Stat5a/b we have developed a GEMM harboring a flox Stat3-Stat5a/b allele (Stat5/3loxP/loxP mice) and generated mice lacking Stat3 and Stat5a/b in hepatocytes (Stat5/3Δhep/Δhep). Stat5/3Δhep/Δhep mice exhibited a marked reduction of STAT3, STAT5A and STAT5B proteins in the liver and developed steatosis, a phenotype that resembles mice lacking Stat5a/b in hepatocytes. In addition, embryonic deletion of Stat3 and Stat5a/b (Stat5/3Δ/Δ mice) resulted in lethality, similar to Stat3Δ/Δ mice. This data illustrates that Stat5/3loxP/loxP mice are functional and can be used as a valuable tool to model the combined inhibition of Stat3 and Stat5a/b in tumorigenesis and other diseases.

Abstract 2199: Left Ventricular Diastolic Function Impacts Age Based Differences in Exercise Capacity

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Jasmine Grewal ◽  
Robert B McCully ◽  
Carolyn S Lam ◽  
Garvan C Kane ◽  
Patricia A Pellikka
Keyword(s):  
Diastolic Dysfunction ◽  
Diastolic Function ◽  
Exercise Capacity ◽  
Multivariate Analyses ◽  
Large Population ◽  
Left Ventricular ◽  
Exercise Intolerance ◽  
Exercise Echocardiography ◽  
Clinical Predictors ◽  
The Impact

Limited information exists regarding the echocardiographic and clinical predictors of exercise capacity and their effects on exercise with advancing age or by sex. We hypothesized that LV diastolic function (DF) impacts exercise capacity to a greater degree with advancing age. This was a prospective cohort study of consecutive patients undergoing routine exercise echocardiography with the Bruce protocol (n=2955). DF assessments at rest and exercise were performed. Those with echocardiographic exercise-induced ischemia and significant valvular disease were excluded. Univariate and multivariate analyses were conducted to determine the strongest echocardiographic and clinical predictors of exercise capacity (METs). Results were reported as unstandardized β coefficient (Standard Error) as outlined beside each variable. Age and sex interactions of these predictors with exercise capacity were determined. The strongest independent multivariate predictors of exercise capacity were female vs. male sex [−1.98 (0.07), p<0.0001], body mass index >30 kg/m 2 [−1.24 (0.08), p<0.0001], age per 10 year increment [−0.85 (0.01), p<0.0001], mild resting diastolic dysfunction vs. normal [−0.70 (0.10), p<0.0001], and moderate/severe resting diastolic dysfunction vs. normal [−1.3 (0.13), p<0.0001]. LV filling pressures measured by a resting E/e’ ≥ 15 [−0.42 (0.14), p=0.004] or exercise E/e’≥ 15 [−0.31 (0.14), p<0.0001] similarly predicted a reduction in exercise capacity, each in separate multivariate analyses. The impact of impaired relaxation and left ventricular filling pressures on exercise capacity increased with advancing age (p<0.001 and p=0.02 respectively), and was most marked after age 50. These predictors had a similar negative effect on exercise capacity among men and women (p=NS). In conclusion, in this large population referred for exercise echocardiography and not limited by ischemia, resting DF and resting/exercise LV filling pressures independently predicted exercise capacity. The increasingly potent effect of impaired relaxation and exercise LV filling pressures with advancing age suggest that DF plays an important role in the development of exercise intolerance in the elderly.

A STUDY ON THE CORRELATION BETWEEN MORPHOLOGIC ANORMALIES AND LEFT VENTRICULAR DIASTOLIC FUNCTION IN DILATED CARDIO-MYOPATHY

2011 ◽  
pp. 137-144
Author(s):  
Thi Ngoc Ha Hoang ◽  
Anh Vu Nguyen ◽  
Minh Loi Hoang ◽  
Cuu Long Nguyen ◽  
Thi Thuy Hang Nguyen
Keyword(s):  
Pulmonary Artery ◽  
Dilated Cardiomyopathy ◽  
Diastolic Dysfunction ◽  
Diastolic Function ◽  
Pulmonary Arteries ◽  
Left Ventricular ◽  
University Hospital ◽  
Cross Sectional ◽  
X Ray ◽  
Key Words Dilated Cardiomyopathy

Purposes: Describe the morphological and diastolic function of left ventricular changes in the patients with dilated cardiomyopathy (DCM) on US, X-ray findings, and Evaluate the correlation between morphology and diastolic function of left ventricular. Materials and method: Cross sectional study from Dec 2009 to Aug 2010, on 39 patients with dilated cardiomyopathy were evaluated at the University Hospital of Hue College of Medical and Pharmaceutical. Results: 1. X-ray and US findings characteristics of DCM is significantly increased in diameter of L, H and mG; LVM, LVMI, LVDd and LAD. 2. The pression of pulmonary artery has been significantly increased with redistribution pulmonary arteries in 61.5% cases and 23.1% have reversed pulmonary artery distribution. 3. DCM have diastolic dysfunction in 100% patients, including severe disorders to 61.5%; the restrictive dysfunction has ratio E/A>2 and E/Em average was 23.89± 17.23. 4.The correlation between the morphology and function in DCM: the diameter of H and L on the X-ray, LAD and ratio LA/AO on US correlated with the level of diastolic dysfunction (p< 0.05). All three radiographic parameters on the radio standard (H, L, the index Cardio/Thoracic) and LVDd on US have negative correlated with EF and FS with p <0.05. Key words: dilated cardiomyopathy, diastolic dysfunction, cardiac tissue Doppler, reversed pulmonary artery distribution

scholarly journals DIPG-41. DISSECTING THE MECHANISTIC BASIS FOR ACVR1 AND PIK3CA MUTATION CO-OCCURRENCE IN DIFFUSE MIDLINE GLIOMAS USING GENETICALLY ENGINEERED MOUSE MODELS

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii295-iii295
Author(s):  
Annette Wu ◽  
Tak Mak ◽  
Jerome Fortin
Keyword(s):  
Mouse Models ◽  
Pik3ca Mutation ◽  
Cell Lineage ◽  
Gene Expression Signature ◽  
Genetically Engineered ◽  
Genetically Engineered Mouse Models ◽  
Dismal Prognosis ◽  
Human Pathology ◽  
Genes Encoding ◽  
Mechanistic Basis

Abstract Diffuse midline gliomas (DMGs) are aggressive childhood brain tumors with a dismal prognosis. Most of these tumors carry K27M mutations in histone H3-encoding genes, particularly H3F3A and HIST1H3B. In addition, activating mutations in ACVR1 and PIK3CA co-occur in a subset of DMGs. To understand how these lesions drive the development of DMGs, we generated genetically engineered mouse models in which Acvr1G328V, Hist1h3bK27M, and Pik3caH1047R are targeted to the OLIG2-expressing cell lineage. Animals carrying Acvr1G328V and Pik3caH1047R, with (“AHPO”) or without (“APO”) Hist1h3bK27M, developed high-grade diffuse gliomas involving midline and forebrain regions. Neither Acvr1G328V nor Pik3caH1047R drove tumorigenesis by themselves, but Acvr1G328V was sufficient to cause oligodendroglial differentiation arrest, pointing to a role in the earliest stages of gliomas formation. Transcriptomic analyses of AHPO and APO tumors indicated a predominantly proneural and oligodendrocyte precursor-like gene expression signature, consistent with the corresponding human pathology. Genes encoding transcription factors (TFs) with dual roles in controlling glial and neuronal differentiation were upregulated in tumors. Some of these genes were mildly induced by Acvr1G328V alone. Functional experiments using CRISPR/Cas9-mediated gene editing in patient-derived cell lines confirmed a role for some of these TFs in controlling DMG cell fitness. Overall, our results suggest that Pik3caH1047R consolidates Acvr1G328V-induced glial differentiation arrest to drive DMG development and progression.

scholarly journals Delineating the molecular and histological events that govern right ventricular recovery using a novel mouse model of pulmonary artery de-banding

2019 ◽  
Vol 116 (10) ◽  
pp. 1700-1709 ◽  
Author(s):  
Mario Boehm ◽  
Xuefei Tian ◽  
Yuqiang Mao ◽  
Kenzo Ichimura ◽  
Melanie J Dufva ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Mouse Model ◽  
Pulmonary Artery ◽  
Right Ventricular ◽  
Exercise Capacity ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Sequence Of Events ◽  
Reverse Remodelling ◽  
Rv Function

Abstract Aims The temporal sequence of events underlying functional right ventricular (RV) recovery after improvement of pulmonary hypertension-associated pressure overload is unknown. We sought to establish a novel mouse model of gradual RV recovery from pressure overload and use it to delineate RV reverse-remodelling events. Methods and results Surgical pulmonary artery banding (PAB) around a 26-G needle induced RV dysfunction with increased RV pressures, reduced exercise capacity and caused liver congestion, hypertrophic, fibrotic, and vascular myocardial remodelling within 5 weeks of chronic RV pressure overload in mice. Gradual reduction of the afterload burden through PA band absorption (de-PAB)—after RV dysfunction and structural remodelling were established—initiated recovery of RV function (cardiac output and exercise capacity) along with rapid normalization in RV hypertrophy (RV/left ventricular + S and cardiomyocyte area) and RV pressures (right ventricular systolic pressure). RV fibrotic (collagen, elastic fibres, and vimentin+ fibroblasts) and vascular (capillary density) remodelling were equally reversible; however, reversal occurred at a later timepoint after de-PAB, when RV function was already completely restored. Microarray gene expression (ClariomS, Thermo Fisher Scientific, Waltham, MA, USA) along with gene ontology analyses in RV tissues revealed growth factors, immune modulators, and apoptosis mediators as major cellular components underlying functional RV recovery. Conclusion We established a novel gradual de-PAB mouse model and used it to demonstrate that established pulmonary hypertension-associated RV dysfunction is fully reversible. Mechanistically, we link functional RV improvement to hypertrophic normalization that precedes fibrotic and vascular reverse-remodelling events.

scholarly journals Mutational landscape of EGFR-, MYC-, and Kras-driven genetically engineered mouse models of lung adenocarcinoma

2016 ◽  
Vol 113 (42) ◽  
pp. E6409-E6417 ◽  
Author(s):  
David G. McFadden ◽  
Katerina Politi ◽  
Arjun Bhutkar ◽  
Frances K. Chen ◽  
Xiaoling Song ◽  
...  
Keyword(s):  
Lung Adenocarcinoma ◽  
Mouse Models ◽  
Cancer Progression ◽  
Large Scale ◽  
Human Cancer ◽  
Genetically Engineered ◽  
Model Systems ◽  
Driver Mutations ◽  
Genetic Profile ◽  
Genetically Engineered Mouse Models

Genetically engineered mouse models (GEMMs) of cancer are increasingly being used to assess putative driver mutations identified by large-scale sequencing of human cancer genomes. To accurately interpret experiments that introduce additional mutations, an understanding of the somatic genetic profile and evolution of GEMM tumors is necessary. Here, we performed whole-exome sequencing of tumors from three GEMMs of lung adenocarcinoma driven by mutant epidermal growth factor receptor (EGFR), mutant Kirsten rat sarcoma viral oncogene homolog (Kras), or overexpression of MYC proto-oncogene. Tumors from EGFR- and Kras-driven models exhibited, respectively, 0.02 and 0.07 nonsynonymous mutations per megabase, a dramatically lower average mutational frequency than observed in human lung adenocarcinomas. Tumors from models driven by strong cancer drivers (mutant EGFR and Kras) harbored few mutations in known cancer genes, whereas tumors driven by MYC, a weaker initiating oncogene in the murine lung, acquired recurrent clonal oncogenic Kras mutations. In addition, although EGFR- and Kras-driven models both exhibited recurrent whole-chromosome DNA copy number alterations, the specific chromosomes altered by gain or loss were different in each model. These data demonstrate that GEMM tumors exhibit relatively simple somatic genotypes compared with human cancers of a similar type, making these autochthonous model systems useful for additive engineering approaches to assess the potential of novel mutations on tumorigenesis, cancer progression, and drug sensitivity.

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