Clinical Focus
- Pediatric Cardiology
Professional Education
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Board Certification: American Board of Pediatrics, Pediatric Cardiology (2022)
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Residency: Stanford Health Care at Lucile Packard Children's Hospital (2017) CA
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Fellowship: Stanford School of Medicine (2021) CA
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Board Certification: American Board of Pediatrics, Pediatrics (2018)
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Medical Education: University of California at San Francisco School of Medicine (2015) CA
All Publications
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Comparing the Efficacy of Myosin Inhibition Versus Thin Filament Calcium Desensitization for Treatment of Pediatric Restrictive Cardiomyopathy Using a Patient-Derived hiPSC Model.
Circulation. Genomic and precision medicine
2025: e005464
View details for DOI 10.1161/CIRCGEN.125.005464
View details for PubMedID 41221584
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Empagliflozin Improves Cardiomyocyte Function in Phospholamban-R14del Cardiomyopathy by Regulating Calcium/Calmodulin-Stimulated Protein Kinase II Activity and Apoptosis.
Journal of the American Heart Association
2025: e042432
View details for DOI 10.1161/JAHA.125.042432
View details for PubMedID 41147384
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Scaled multidimensional assays of variant effect identify sequence-function relationships in hypertrophic cardiomyopathy.
bioRxiv : the preprint server for biology
2025
Abstract
Background: An estimated 1 in 500 people live with hypertrophic cardiomyopathy (HCM), a disease for which genetic diagnosis can identify family members at risk, and increasingly guide therapy. Mutations in the myosin binding protein C3 ( MYBPC3 ) gene account for a significant proportion of HCM cases. However, many of these variants are classified as variants of uncertain significance (VUS), complicating clinical decision-making. Scalable methods for variant interpretation in disease-specific cell types are crucial for understanding variant impact and uncovering disease mechanisms.Methods: We developed a scaled multidimensional mapping strategy to evaluate the functional impact of variants across a critical domain of MYBPC3. We incorporate saturation base editing at the native MYBPC3 locus, a long-read RNA sequencing-enabled assay of variant splice effects, and measurements of HCM-relevant phenotypes, including MYBPC3 abundance, hypertrophic signaling, and ubiquitin-proteasome function in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs).Results: Our multidimensional mapping strategy enabled high-resolution functional analysis of MYBPC3 variants in iPSC-CMs. Targeted transient base editing generated a comprehensive variant library at the native locus, capturing diverse variant effects on cellular HCM-relevant phenotypes. Our massively parallel splicing assay identified novel splice-disrupting variants. Integration of functional assays revealed that decreased MYBPC3 abundance is a key driver of HCM-related phenotypes. In parallel, downregulation of protein degradation was observed as a compensatory response to MYBPC3 loss of function, and novel disease mechanisms were identified for missense variants near a critical binding domain, underscoring their contribution to pathogenesis. Bayesian estimates of variant effects enable the reclassification of clinical variants.Conclusions: This work provides a platform for extending genome engineering in iPSCs to multiplexed assays of variant effects across diverse disease-relevant cellular phenotypes, enhancing the understanding of variant pathogenicity and uncovering novel biological mechanisms that could inform therapeutic strategies.
View details for DOI 10.1101/2025.05.23.655878
View details for PubMedID 40501845
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Human iPSC modeling of heart disease for drug development.
Cell chemical biology
2021; 28 (3): 271–82
Abstract
Human induced pluripotent stem cells (hiPSCs) have emerged as a promising platform for pharmacogenomics and drug development. In cardiology, they make it possible to produce unlimited numbers of patient-specific human cells that reproduce hallmark features of heart disease in the culture dish. Their potential applications include the discovery of mechanism-specific therapeutics, the evaluation of safety and efficacy in a human context before a drug candidate reaches patients, and the stratification of patients for clinical trials. Although this new technology has the potential to revolutionize drug discovery, translational hurdles have hindered its widespread adoption for pharmaceutical development. Here we discuss recent progress in overcoming these hurdles that should facilitate the use of hiPSCs to develop new medicines and individualize therapies for heart disease.
View details for DOI 10.1016/j.chembiol.2021.02.016
View details for PubMedID 33740432
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In Vivo Visualization of Cardiomyocyte Apicobasal Polarity Reveals Epithelial to Mesenchymal-like Transition during Cardiac Trabeculation
CELL REPORTS
2016; 17 (10): 2687-2699
Abstract
Despite great strides in understanding cardiac trabeculation, many mechanistic aspects remain unclear. To elucidate how cardiomyocyte shape changes are regulated during this process, we engineered transgenes to label their apical and basolateral membranes. Using these tools, we observed that compact-layer cardiomyocytes are clearly polarized while delaminating cardiomyocytes have lost their polarity. The apical transgene also enabled the imaging of cardiomyocyte apical constriction in real time. Furthermore, we found that Neuregulin signaling and blood flow/cardiac contractility are required for cardiomyocyte apical constriction and depolarization. Notably, we observed the activation of Notch signaling in cardiomyocytes adjacent to those undergoing apical constriction, and we showed that this activation is positively regulated by Neuregulin signaling. Inhibition of Notch signaling did not increase the percentage of cardiomyocytes undergoing apical constriction or of trabecular cardiomyocytes. These studies provide information about cardiomyocyte polarization and enhance our understanding of the complex mechanisms underlying ventricular morphogenesis and maturation.
View details for DOI 10.1016/j.celrep.2016.11.023
View details for Web of Science ID 000390894200017
View details for PubMedID 27926871
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High-resolution imaging of cardiomyocyte behavior reveals two distinct steps in ventricular trabeculation
DEVELOPMENT
2014; 141 (3): 585–93
Abstract
Over the course of development, the vertebrate heart undergoes a series of complex morphogenetic processes that transforms it from a simple myocardial epithelium to the complex 3D structure required for its function. One of these processes leads to the formation of trabeculae to optimize the internal structure of the ventricle for efficient conduction and contraction. Despite the important role of trabeculae in the development and physiology of the heart, little is known about their mechanism of formation. Using 3D time-lapse imaging of beating zebrafish hearts, we observed that the initiation of cardiac trabeculation can be divided into two processes. Before any myocardial cell bodies have entered the trabecular layer, cardiomyocytes extend protrusions that invade luminally along neighboring cell-cell junctions. These protrusions can interact within the trabecular layer to form new cell-cell contacts. Subsequently, cardiomyocytes constrict their abluminal surface, moving their cell bodies into the trabecular layer while elaborating more protrusions. We also examined the formation of these protrusions in trabeculation-deficient animals, including erbb2 mutants, tnnt2a morphants, which lack cardiac contractions and flow, and myh6 morphants, which lack atrial contraction and exhibit reduced flow. We found that, compared with cardiomyocytes in wild-type hearts, those in erbb2 mutants were less likely to form protrusions, those in tnnt2a morphants formed less stable protrusions, and those in myh6 morphants extended fewer protrusions per cell. Thus, through detailed 4D imaging of beating hearts, we have identified novel cellular behaviors underlying cardiac trabeculation.
View details for DOI 10.1242/dev.098632
View details for Web of Science ID 000330573500010
View details for PubMedID 24401373
View details for PubMedCentralID PMC3899815
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Uncovering the Molecular and Cellular Mechanisms of Heart Development Using the Zebrafish
ANNUAL REVIEW OF GENETICS, VOL 46
edited by Bassler, B. L.
2012; 46: 397–418
Abstract
Over the past 20 years, the zebrafish has emerged as a powerful model organism for studying cardiac development. Its ability to survive without an active circulation and amenability to forward genetics has led to the identification of numerous mutants whose study has helped elucidate new mechanisms in cardiac development. Furthermore, its transparent, externally developing embryos have allowed detailed cellular analyses of heart development. In this review, we discuss the molecular and cellular processes involved in zebrafish heart development from progenitor specification to development of the valve and the conduction system. We focus on imaging studies that have uncovered the cellular bases of heart development and on zebrafish mutants with cardiac abnormalities whose study has revealed novel molecular pathways in cardiac cell specification and tissue morphogenesis.
View details for DOI 10.1146/annurev-genet-110711-155646
View details for Web of Science ID 000311568300018
View details for PubMedID 22974299
View details for PubMedCentralID PMC6982417
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A dual role for ErbB2 signaling in cardiac trabeculation
DEVELOPMENT
2010; 137 (22): 3867–75
Abstract
Cardiac trabeculation is a crucial morphogenetic process by which clusters of ventricular cardiomyocytes extrude and expand into the cardiac jelly to form sheet-like projections. Although it has been suggested that cardiac trabeculae enhance cardiac contractility and intra-ventricular conduction, their exact function in heart development has not been directly addressed. We found that in zebrafish erbb2 mutants, which we show completely lack cardiac trabeculae, cardiac function is significantly compromised, with mutant hearts exhibiting decreased fractional shortening and an immature conduction pattern. To begin to elucidate the cellular mechanisms of ErbB2 function in cardiac trabeculation, we analyzed erbb2 mutant hearts more closely and found that loss of ErbB2 activity resulted in a complete absence of cardiomyocyte proliferation during trabeculation stages. In addition, based on data obtained from proliferation, lineage tracing and transplantation studies, we propose that cardiac trabeculation is initiated by directional cardiomyocyte migration rather than oriented cell division, and that ErbB2 cell-autonomously regulates this process.
View details for DOI 10.1242/dev.053736
View details for Web of Science ID 000283671100015
View details for PubMedID 20978078
View details for PubMedCentralID PMC3049280
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Competitive control of independent programs of tumor necrosis factor receptor-induced cell death by TRADD and RIP1
MOLECULAR AND CELLULAR BIOLOGY
2006; 26 (9): 3505–13
Abstract
Stimulation of tumor necrosis factor receptor 1 (TNFR1) can initiate several cellular responses, including apoptosis, which relies on caspases, necrotic cell death, which depends on receptor-interacting protein kinase 1 (RIP1), and NF-kappaB activation, which induces survival and inflammatory responses. The TNFR-associated death domain (TRADD) protein has been suggested to be a crucial signal adaptor that mediates all intracellular responses from TNFR1. However, cells with a genetic deficiency of TRADD are unavailable, precluding analysis with mature immune cell types. We circumvented this problem by silencing TRADD expression with small interfering RNA. We found that TRADD is required for TNFR1 to induce NF-kappaB activation and caspase-8-dependent apoptosis but is dispensable for TNFR1-initiated, RIP1-dependent necrosis. Our data also show that TRADD and RIP1 compete for recruitment to the TNFR1 signaling complex and the distinct programs of cell death. Thus, TNFR1-initiated intracellular signals diverge at a very proximal level by the independent association of two death domain-containing proteins, RIP1 and TRADD. These single transducers determine cell fate by triggering NF-kappaB activation, apoptosis, and nonapoptotic death signals through separate and competing signaling pathways.
View details for DOI 10.1128/MCB.26.9.3505-3513.2006
View details for Web of Science ID 000236993300014
View details for PubMedID 16611992
View details for PubMedCentralID PMC1447428
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Histone H2AX phosphorylation is dispensable for the initial recognition of DNA breaks
NATURE CELL BIOLOGY
2003; 5 (7): 675–U51
Abstract
Histone H2AX is rapidly phosphorylated in the chromatin micro-environment surrounding a DNA double-strand break (DSB). Although H2AX deficiency is not detrimental to life, H2AX is required for the accumulation of numerous essential proteins into irradiation induced foci (IRIF). However, the relationship between IRIF formation, H2AX phosphorylation (gamma-H2AX) and the detection of DNA damage is unclear. Here, we show that the migration of repair and signalling proteins to DSBs is not abrogated in H2AX(-/-) cells, or in H2AX-deficient cells that have been reconstituted with H2AX mutants that eliminate phosphorylation. Despite their initial recruitment to DSBs, numerous factors, including Nbs1, 53BP1 and Brca1, subsequently fail to form IRIF. We propose that gamma-H2AX does not constitute the primary signal required for the redistribution of repair complexes to damaged chromatin, but may function to concentrate proteins in the vicinity of DNA lesions. The differential requirements for factor recruitment to DSBs and sequestration into IRIF may explain why essential regulatory pathways controlling the ability of cells to respond to DNA damage are not abolished in the absence of H2AX.
View details for DOI 10.1038/ncb1004
View details for Web of Science ID 000183911600019
View details for PubMedID 12792649