Biology subjects

Seidman, J.

Publications and source records attributed to Seidman, J..

7 recordsLinked to original sources

bioRxiv2025

Thick filament molecular interfaces play a critical role in pathogenesis of hypertrophic and dilated cardiomyopathy

Hypertrophic (HCM) and dilated (DCM) cardiomyopathy variants in genes encoding the myosin heavy chain (MYH7), myosin light chains (MYL2 and MYL3), and cardiac myosin binding protein-C (cMyBP-C, MYBPC3) lead to cardiac hypertrophy or dilatation, with abnormal contractility, relaxation, and energy consumption. Here we defined the structural consequences of >200 pathogenic and benign missense variants in these genes by mapping variants onto a cryo-EM-based atomic model of the human cardiac thick filament. We identified HCM variants residing in 31 molecular interfaces of the complex thick filament interactome, including the two main interfaces of the myosin interacting-heads motif (IHM), and interfaces involving the myosin heavy chain, essential and regulatory light chains, and cMyBP-C. Pathogenic DCM missense variants are rare, and altered only interfaces involving the myosin IHM and tails. None of the 21 variants classified as benign were within interfaces. We demonstrate earlier disease onset and adverse outcomes in HCM patients with pathogenic variants within versus outside of molecular interfaces, emphasizing their importance in normal thick filament function and improving risk stratification of patients. The dissimilar distribution of DCM and HCM variants could explain the different features of the two phenotypes.

biophysics↗

bioRxiv2024

Genes of the fatty acid oxidation pathway are upregulated in female as compared to male cardiomyocytes

Human females and males differ in cardiac physiology and pathology, even after controlling for sex differences in anthropometrics, lifestyle, and environment. For example, females and males differ in cardiac stroke volume and ventricular thickness, and they exhibit different rates and symptoms of cardiovascular disease. Less is understood about molecular differences in female and male hearts, such as sex differences in gene expression. Here we present an integrative framework utilizing bulk and single-nucleus RNA-sequencing data to study sex differences in the cardiac transcriptome. We show that genes of the fatty acid oxidation (FAO) pathway, the primary source of energy in the heart, are expressed more highly in healthy female than in healthy male hearts. We demonstrate that this sex difference is due to cardiomyocyte-specific, female-biased expression of FAO genes and cannot be explained by sex differences in cardiac cellular composition or number of mitochondria, where FAO takes place. Finally, we observe increased cardiac flux and energetic utilization of free fatty acids in female compared to male hearts. Overall, our results demonstrate that male and female human hearts exhibit fundamental differences in metabolism that likely contribute to sex differences in cardiac physiology and pathology.

genomics↗

bioRxiv2024

Endocardial primary cilia and blood flow are required for regulation of EndoMT during endocardial cushion development

Blood flow is critical for heart valve formation, and cellular mechanosensors are essential to translate flow into transcriptional regulation of development. Here, we identify a role for primary cilia in vivo in the spatial regulation of cushion formation, the first stage of valve development, by regionally controlling endothelial to mesenchymal transition (EndoMT) via modulation of Kruppel-like Factor 4 (Klf4). We find that high shear stress intracardiac regions decrease endocardial ciliation over cushion development, correlating with KLF4 downregulation and EndoMT progression. Mouse embryos constitutively lacking cilia exhibit a blood-flow dependent accumulation of KLF4 in these regions, independent of upstream left-right abnormalities, resulting in impaired cushion cellularization. snRNA-seq revealed that cilia KO endocardium fails to progress to late-EndoMT, retains endothelial markers and has reduced EndoMT/mesenchymal genes that KLF4 antagonizes. Together, these data identify a mechanosensory role for endocardial primary cilia in cushion development through regional regulation of KLF4.

developmental biology↗

bioRxiv2023

Short-term Pre-operative Methionine Restriction Induces Browning of Perivascular Adipose Tissue and Improves Vein Graft Remodeling in Mice

Short-term preoperative methionine restriction (MetR) shows promise as a translatable strategy to modulate the bodys response to surgical injury. Its application, however, to improve post-interventional vascular remodeling remains underexplored. Here, we find that MetR protects from arterial intimal hyperplasia in a focal stenosis model and adverse vascular remodeling after vein graft surgery. RNA sequencing reveals that MetR enhances the brown adipose tissue phenotype in arterial perivascular adipose tissue (PVAT) and induces it in venous PVAT. Specifically, PPAR- was highly upregulated in PVAT-adipocytes. Furthermore, MetR dampens the post-operative pro-inflammatory response to surgery in PVAT-macrophages in vivo and in vitro. This study shows for the first time that the detrimental effects of dysfunctional PVAT on vascular remodeling can be reversed by MetR, and identifies pathways involved in browning of PVAT. Furthermore, we demonstrate the potential of short-term pre-operative MetR as a simple intervention to ameliorate vascular remodeling after vascular surgery. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/565269v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@112f51aorg.highwire.dtl.DTLVardef@1998bd8org.highwire.dtl.DTLVardef@1ac5046org.highwire.dtl.DTLVardef@1ca4c87_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

bioRxiv2022

Human iPSC-CMs and in-silico technologies define mechanisms and accelerate targeted pharmacogenetics in hypertrophic cardiomyopathy

Cardiomyopathies have unresolved genotype-phenotype relationships and lack disease-specific treatments. Here we identify genotype-specific pathomechanisms and therapeutic targets combining experimental hiPSC-CM modelling and human-based cardiac electromechanical in-silico modelling and simulation bridging from specific mutations to clinical biomarkers. We select hypertrophic cardiomyopathy as a challenge for this approach and study genetic variations that mutate proteins of the thick (MYH7R403Q/+) and thin filaments (TNNT2R92Q/+, TNNI3R21C/+) of the cardiac sarcomere. We show that destabilisation of myosin super relaxation drives disease in MYH7R403Q/+ with secondary effects on thin filament activation, which are corrected by Mavacamten. Thin filament variants TNNT2R92Q/+ and TNNI3R21C/+ share calcium regulation-related pathomechanisms, for which Mavacamten provides incomplete salvage. We define the ideal characteristics of a novel thin filament-targeting compound and show its efficacy in-silico. We demonstrate that hybrid human-based hiPSC-CM and in-silico studies accelerate pathomechanism discovery and classification testing, improving clinical interpretation of genetic variants, and directing rational therapeutic targeting and design.

bioengineering↗

bioRxiv2018

MYBPC3 Mutations cause Hypertrophic Cardiomyopathy by Dysregulating Myosin: Implications for Therapy

The mechanisms by which truncating mutations in MYBPC3 (encoding cardiac myosin binding protein-C; cMyBPC) or myosin missense mutations cause hyper-contractility and poor relaxation in hypertrophic cardiomyopathy (HCM) are incompletely understood. Using genetic and biochemical approaches we explored how depletion of cMyBPC altered sarcomere function. We demonstrate that stepwise loss of cMyBPC resulted in reciprocal augmentation of myosin contractility. Direct attenuation of myosin function, via a damaging missense variant (F764L) that causes dilated cardiomyopathy (DCM) normalized the increased contractility from cMyBPC depletion. Depletion of cMyBPC also altered dynamic myosin conformations during relaxation - enhancing the myosin state that enables ATP hydrolysis and thin filament interactions while reducing the super relaxed conformation associated with energy conservation. MYK-461, a pharmacologic inhibitor of myosin ATPase, rescued relaxation deficits and restored normal contractility in mouse and human cardiomyocytes with MYBPC3 mutations. These data define dosage-dependent effects of cMyBPC on myosin that occur across all phases of the cardiac cycle as the pathophysiologic mechanisms by which MYBPC3 truncations cause HCM. Therapeutic strategies to attenuate cMyBPC activity may rescue depressed cardiac contractility in DCM patients, while inhibiting myosin by MYK-461 should benefit the substantial proportion of HCM patients with MYBPC3 mutations.\n\nOne Sentence SummaryAnalyses of cardiomyocytes with hypertrophic cardiomyopathy mutations in MYBPC3 reveal that these directly activate myosin contraction by disrupting myosin states of relaxation, and that genetic or pharmacological manipulation of myosin therapeutically abates the effects of MYBPC3 mutations.

genetics↗

bioRxiv2017

Cardiac enriched BAF chromatin remodeling complex subunit Baf60c regulates gene expression programs essential for heart development and function

How gene networks controlling organ-specific properties are modulated by chromatin remodeling complexes is not well understood. Baf60c (Smarcd3) encodes a cardiac-enriched subunit of the SWI/SNF-like BAF chromatin complex. Its role throughout heart development is not fully understood. We show that constitutive loss of Baf60c leads to embryonic cardiac hypoplasia and pronounced cardiac dysfunction. Conditional deletion of Baf60c in cardiomyocytes results in postnatal dilated cardiomyopathy with impaired contractile function. Baf60c regulates a gene expression program that includes genes encoding contractile proteins, modulators of sarcomere function, and cardiac metabolic genes. Many of the genes deregulated in Baf60c null embryos are targets of the MEF2/SRF co-factor Myocardin (MYOCD). In a yeast two-hybrid screen we identify MYOCD as a BAF60c interacting factor; we show that BAF60c and MYOCD directly and functionally interact. We conclude that Baf60c is essential for coordinating a program of gene expression that regulates the fundamental functional properties of cardiomyocytes.

developmental biology↗