Biology subjects

de la Pompa, J. L.

Publications and source records attributed to de la Pompa, J. L..

10 recordsLinked to original sources

bioRxiv2026

Abnormal ventricular wall patterning precedes and drives MYBPC3 hypertrophic cardiomyopathy

BACKGROUNDExcessive trabeculations and myocardial crypts are recurrent features across cardiomyopathies, yet their developmental origins and clinical significance remain poorly defined. To reveal the link between cardiac morphogenesis and disease, we generated humanized mouse models carrying patient-derived MYBPC3 frameshift mutations associated with overlapping hypertrophic cardiomyopathy (HCM) and left ventricular non-compaction (LVNC). METHODSWe applied CRISPR-Cas9 to introduce distinct MYBPC3 frameshift alleles into the mouse genome and performed comprehensive phenotypic and transcriptomic profiling from fetal life through adulthood. RESULTSAdult homozygous Mybpc3 frameshift mutant mice like humans displayed hallmark HCM; however, without LVNC. Fetal and neonatal mutant hearts exhibited markedly enlarged ventricular trabeculae and crypts that progressed postnatally into the observed adult hypertrophy. Transcriptomic analysis revealed stage-specific dysregulation of oxidative metabolism, nonsense-mediated decay (NMD), and cell cycle pathways, peaking at postnatal days 1 and 7, indicating that these stages represent critical time points in disease onset. The persistent NMD signature, also observed in phenotype-negative heterozygotes, suggests a compensatory stress response. Enlarged trabeculae exhibited 2-fold increased trabecular cardiomyocyte proliferation, reversing the normal compact-trabecular proliferative gradient and leading to impaired ventricular compaction in neonates. Hey2CreERT2 lineage tracing demonstrated invasion of Hey2+ compact cardiomyocytes into the trabeculae and ectopic trabecular expression of the Prdm16 transcription factor, indicating defective ventricular wall patterning and maturation. Postnatally, Hey2+-derived cardiomyocytes became restricted to the outer/compact myocardium in mutants, while the inner/trabecular myocardium underwent accelerated hypertrophy concurrent with Prdm16 downregulation. Mice with a Mybpc3 missense variant also exhibited Hey2+ myocardial lineage expansion into trabeculae but no increased proliferation, implicating additional mechanisms beyond Hey2 regulation. Postnatal Prdm16 restoration, via transgenic expression in Mybpc3-null mice effectively attenuated hypertrophy, establishing a causal link between Mybpc3 loss, Prdm16 decline, and pathological remodeling. CONCLUSIONSMybpc3 governs ventricular wall maturation by regulating cardiomyocyte proliferation, patterning, and maturation, partly via Prdm16. Disruption of these developmental programs precedes and drives adult HCM, highlighting a developmental role for sarcomeric proteins, and revealing postnatal Prdm16 modulation as an antihypertrophic therapeutic strategy.

developmental biology↗

bioRxiv2025

Patterning defects in mice with defective ventricular wall maturation and cardiomyopathy

Ventricular chamber development involves the coordinated maturation of diverse cell populations. In the human fetal heart, single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics reveal marked regional gene expression differences. In contrast, the mouse ventricular wall appears more homogeneous, except for a transient hybrid cardiomyocyte population co-expressing compact (Hey2) and trabecular (Irx3, Nppa, Bmp10) markers, indicating a transitional lineage state. To further investigate this, we used in situ hybridization (ISH) to examine the expression of a selected set of markers in normal and left ventricular non-compaction cardiomyopathy (LVNC) mouse models. In developing mouse ventricles, the expression of key marker genes was largely restricted to two wide myocardial domains-- compact and trabecular myocardium--suggesting a less complex regional organization than human fetal heart. Other markers labelled endocardial and coronary endothelial cells rather than cardiomyocytes, differing from patterns observed in the human heart. In the LVNC model, various markers exhibited altered spatial expression, indicating that precise regional organization of gene expression is critical for normal ventricular wall maturation. These findings underscore the critical role of spatially regulated gene programs in ventricular chamber development and point to their potential involvement in cardiomyopathy pathogenesis.

developmental biology↗

bioRxiv2024

Cardiac electrical abnormalities in a mouse model of left ventricular non-compaction cardiomyopathy

Mutations in MINDBOMB 1 (MIB1), encoding an E3 ubiquitin ligase of the NOTCH signaling pathway, cause left ventricular noncompaction cardiomyopathy (LVNC) in mice and humans, increasing the risk of arrhythmia and left ventricular dysfunction. This study aimed to investigate the effect of MIB1 mutations on cardiac electrical activity. We examined male Mib1flox;Tnnt2Cre mice, a disease model of LVNC, and wildtype littermates on the C57BL/6J genetic background. Our results demonstrate that the gap-junction protein connexin43 was delocalized from the intercalated disks to the lateral long axis of Mib1flox;Tnnt2Cre cardiomyocytes. Cardiomyocyte electrophysiology revealed an increase in the Na (INa) peak density at potentials between -50 and -30 mV in Mib1flox;Tnnt2Cremice, with no changes in INa activation or inactivation kinetics. Mib1flox;Tnnt2Cre cardiomyocytes also showed decreases in outward K+ peak currents and currents at the end of depolarizing pulses at potentials [≥]-10 mV and [≥]-20 mV, respectively, and this was accompanied by a lower charge density at [≥]-20 mV. Action potential duration was increased in Mib1flox;Tnnt2Cre cardiomyocytes. The cardiac stress, induced by swimming endurance training or {beta}-adrenergic stimulation with isoproterenol, increases QTc duration in Mib1flox;Tnnt2Cre mice, accompanied by a decrease in T-wave amplitude and area. Swimming endurance training decreased heart rate in wildtype and Mib1flox;Tnnt2Cre mice but was unaffected by long-term isoproterenol treatment. These mouse findings are in agreement with an increased QTc duration found in LVNC patients carrying MIB1 mutations. These results provide insight into the outcomes of LVNC and relate its pathogenicity to impaired ventricular repolarization.

developmental biology↗

bioRxiv2023

A cooperative response to endocardial NOTCH signaling stimulation regulates transcriptional activity during cardiac valve development and disease

BackgroundThe endocardium is a crucial signaling center for cardiac valve development and maturation. Genetic analysis has identified several human endocardial genes whose inactivation leads to bicuspid aortic valve (BAV) formation and/or calcific aortic valve disease (CAVD), but knowledge is very limited about the role played in valve development and disease by non-coding endocardial regulatory regions and upstream factors. MethodsWe manipulated the NOTCH signaling pathway in mouse embryonic endocardial cells by short-term and long-term co-culture with OP9 stromal cells expressing NOTCH ligands and treatment with the {gamma}-secretase inhibitor RO4929097, defining the transcriptional profile associated to each condition. The endocardial chromatin accessibility landscape for each condition was defined by high-throughput sequencing (ATAC-seq) determination of transposase-accessible chromatin. In vitro and in vivo models carrying deletions of different non-coding regulatory elements were generated by CRISPR-Cas9 gene editing. ResultsWe identified primary and secondary transcriptional responses to NOTCH ligands in the mouse embryonic endocardium. By integrating our gene expression data with data from developing valves of mice with NOTCH loss-of-function and from human valve calcification samples, we were able to identify a NOTCH-dependent transcriptional signature in valve development and disease. Further, by defining the endocardial chromatin accessibility landscape after NOTCH pathway manipulation and integrating with in vivo data from developing mouse endocardium and adult human valves, we were able to identify a set of potential non-coding regulatory elements, validate representative candidates, propose co-factors interacting with them, and define the timeframe of their regulatory activity. Analysis of the transcriptional repression driven by NOTCH activation revealed cooperation between the NOTCH and HIPPO pathways in the endocardium during cardiac valve development. ConclusionsTranscriptional regulation in the embryonic endocardium after NOTCH pathway stimulation occurs in a sequential manner and requires the participation of several factors. NOTCH not only triggers the transcriptional activity of the non-coding elements recognized by these factors, but also represses those elements whose activity negatively affects the development and homeostasis of the cardiac valves. Novelty and SignificanceWHAT IS KNOWN? O_LIThe embryonic endocardium is a source of cell types and a crucial signaling center for cardiac valve development and maturation. C_LIO_LIEndocardial NOTCH pathway activity patterns specific cellular behaviors that will give rise to the cardiac valve primordia, guide their maturation, and maintain adult valve homeostasis. C_LIO_LINOTCH signaling abrogation is associated with human valve dysmorphology (bicuspid aortic valve) and adult calcific aortic valve disease (CAVD). C_LI WHAT NEW INFORMATION DOES THIS ARTICLE CONTRIBUTE? O_LIThe existence of a primary transcriptional response after short-term NOTCH activation that is enhanced after sustained ligand stimulation, and a secondary response triggered after long-term NOTCH activation. C_LIO_LIWe have identified a NOTCH-dependent transcriptional signature specific for valve development and disease. C_LIO_LIWe have defined the endocardial chromatin accessibility landscape after NOTCH pathway manipulation, and proposed a set of potential cofactors and the time frame of their activity involved in the NOTCH-dependent transcriptional response. C_LIO_LIWe have identified a set of potential non-coding regulatory elements involved in valve development and disease, and evaluated them in vitro and in vivo. C_LIO_LIWe have identified the cooperation between the NOTCH and HIPPO pathways in the endocardium during cardiac valve development. C_LI

developmental biology↗

bioRxiv2022

Neuregulin1 regulates cardiomyocyte dynamics, proliferation, and maturation during ventricular chamber morphogenesis

BACKGROUNDCardiac ventricles are essential for providing the contractile force of the beating heart throughout life. How the primitive endocardium-layered myocardial projections called trabeculae form and mature into the adult ventricles is of great interest for fundamental biology and regenerative medicine. Trabeculation is dependent on the signaling protein Neuregulin-1 (Nrg1). However, the mechanism of action of Nrg1 and its role in ventricular wall maturation are poorly understood. METHODSIn this study we investigated the functions and downstream mechanisms of Nrg1 signaling during ventricular chamber development using confocal imaging, transcriptomics, and biochemical approaches in mice with conditional cardiac-specific inactivation or overexpression of Nrg1. RESULTSAnalysis of cardiac-specific-Nrg1 mutant mice showed that the transcriptional program underlying cardiomyocyte-oriented cell division and trabeculae formation depends on endocardial Nrg1 to myocardial ErbB2 signaling and pErk activation. Early endothelial loss of Nrg1 and below normal pErk activation diminished cardiomyocyte Pard3 and Crumbs2 protein, and altered cytoskeletal gene expression and organization. These changes were associated with aberrant expression of genes involved in mitotic spindle organization and a directional shift from perpendicular to parallel/obliquely-oriented cardiomyocyte division. Further analysis indicated that Nrg1 is required for trabecular growth and ventricular wall thickening by regulating an epithelial-to-mesenchyme transition (EMT)-like process in cardiomyocytes involving migration, adhesion, cytoskeletal actin turnover, and timely progression through the cell cycle G2/M phase. Ectopic cardiac Nrg1 overexpression and high pErk signaling caused S-phase arrest, maintained high EMT-like gene expression and prolonged trabeculation, blocking compact myocardium maturation. Likewise, alterations of myocardial trabecular patterning resulting from above- or below-normal Nrg1-dependent pErk activation were concomitant with disorganization of the sarcomere actin cytoskeleton. The Nrg1 loss- and gain-of-function transcriptomes were enriched for yes-associated protein-1 (Yap1) gene signatures, identifying Yap1 as a potential downstream effector. Biochemical and imaging data showed that pErk activation and nuclear-cytoplasmic distribution of Yap1 during trabeculation are dependent on Nrg1. CONCLUSIONSThese data establish the Nrg1-ErbB2/4-pErk axis as a crucial regulator of cardiomyocyte cell cycle progression and migration during ventricular development. Moreover, our data identify a Nrg1-dependent signaling cascade that could be leveraged for future cardiac regenerative therapies. Novelty and Significance WHAT IS KNOWN?O_LIMyocardial trabeculae play important roles in ventricular chamber growth, development of the conduction system, and formation of the coronary arteries. C_LIO_LITrabeculae are formed through oriented cell division (OCD), and their growth is driven by directional migration. C_LIO_LIThe membrane glycoprotein Neuregulin-1 (Nrg1) mediates cell-cell signaling and is essential for trabecular development. C_LI WHAT NEW INFORMATION DOES THIS ARTICLE CONTRIBUTE?O_LINrg1 signaling is essential for the expression of cardiomyocyte polarity genes and the organization of the cytoskeleton during the oriented cell division process underlying trabeculation. C_LIO_LINrg1 is required for the formation of the inner ventricular wall but not the coronaries. C_LIO_LINrg1 regulates motility and cell-cycle progression during ventricular wall growth. C_LIO_LIEctopic expression of Nrg1 leads to excessive trabeculation of the myocardium and disrupts compaction. C_LIO_LINrg1 regulates ventricular patterning mediated by cytoskeletal dynamics and modulates pErk-dependent Yap1 S274 phosphorylation during trabeculation. C_LIO_LINrg1 is not required for ventricular compaction. C_LI

developmental biology↗

bioRxiv2021

Midkine-a regulates the formation of a fibrotic scar during zebrafish heart regeneration

The adult zebrafish heart regenerates after injury, unlike the hearts of mammals. Heart cryoinjury triggers the formation of a fibrotic scar that gradually degrades, leading to regeneration. Midkine-a (Mdka) is a multifunctional cytokine that is activated after cardiac injury. Here, we investigated the role of mdka in zebrafish heart regeneration. We show that mdka expression is strongly induced at 1-day post cryoinjury (dpci) throughout the epicardium, whereas by 7 dpci expression has become restricted to epicardial cells covering the injured area. To study the role of mdka in heart regeneration, we generated mdka-knock out (KO) zebrafish strains. Analysis of injured hearts showed that loss of mdka decreased endothelial cell proliferation and resulted in a blockade of heart regeneration characterized by retention of a collagenous scar. Transcriptional analysis revealed increases in collagen transcription and TGF{beta} signalling activity. These results reveal a critical role for mdka in fibrosis regulation during heart regeneration.

developmental biology↗

bioRxiv2020

Fibrous caps in atherosclerosis form by Notch-dependent mechanisms shared with arterial media development

RationaleThe rupture of the fibrous cap in atherosclerotic lesions is the underlying cause of most thrombi leading to heart attack and a frequent cause of stroke. Caps are produced by smooth muscle cells (SMCs) that are recruited to the subendothelial space. We hypothesized that the recruitment mechanisms are likely common to embryonic artery development, which relies prominently on Notch signaling to form the subendothelial layers of medial SMCs. ObjectiveTo analyze the causal roles of the Notch signaling pathway in SMCs for atherogenesis and cap formation. Methods and ResultsNotch elements involved in arterial media development were found expressed in regions of fibrous cap in mouse plaques. To assess the causal role of Notch signaling in cap formation, we studied atherosclerosis in mice in which the Notch pathway was inactivated specifically in SMCs by conditional knockout of the essential effector transcription factor RBPJ. No major effects were observed on plaque size, but the presence of cap SMCs was significantly reduced. Lineage tracing revealed that the accumulation of SMC-derived plaque cells in the cap region was unaltered but that Notch-defective cells failed to re-acquire the SMC phenotype in the cap. To analyze whether the accumulation of SMC-derived cells in atherogenesis requires down-regulation of Notch signaling, we studied atherosclerosis in mice with constitutive Notch signaling in SMCs achieved by conditional expression of the Notch intracellular domain. Forced Notch signaling inhibited the ability of medial SMCs to contribute to plaque cells, including both cap SMCs and osteochondrogenic cells, and significantly reduced atherosclerosis development. ConclusionsSequential loss and gain of Notch signaling is needed to build the cap SMC population. The shared mechanisms with embryonic arterial media assembly suggest that the fibrous cap forms as a neo-media that restores the connection between endothelium and stabilizing SMCs, which is transiently disrupted by atherogenesis.

pathology↗

bioRxiv2020

Loss of Caveolin-1 and caveolae leads to increased cardiac cell stiffness and functional decline of the adult zebrafish heart

Caveolin-1 is the main structural protein of caveolae, small membrane invaginations involved in signal transduction and mechanoprotection. Here, we generated cav1-KO zebrafish lacking Cav1 and caveolae, and investigated the impact of this loss on adult heart function and response to cryoinjury. We found that cardiac function was impaired in adult cav1-KO fish, which showed a significantly decreased ejection fraction and heart rate. Using atomic force microscopy, we detected an increase in the stiffness of epicardial cells and cortical myocardium lacking Cav1/caveolae. This loss of cardiac elasticity might explain the decreased cardiac contraction and function. Surprisingly, cav1-KO mutants were able to regenerate their heart after a cryoinjury but showed a transient decrease in cardiomyocyte proliferation.

developmental biology↗

bioRxiv2018

A human cell model of cardiac pathophysiological valvulogenesis

Genetically modified mice have advanced our understanding of valve development and related pathologies. Yet, little is known regarding human valvulogenesis in health and diseases. Genuine human in vitro models that reproduce valvular (patho)biology are thus needed. We here developed a human pluripotent stem cell-derived model fit to decode the early steps of human valvulogenesis and to recapitulate valve disease traits in a dish.\n\nUsing cellular based, single cell omics-informed and in vivo-validated approaches, we derived a population of pre-valvular endocardial cells from a pluripotent stem cell source. These human prevalvular cells (HPVCs) expressed gene patterns conforming to the atrio-ventricular canal (AVC) endocardium signature originally established in E9.0 mouse embryos. In fact, HPVC treated with BMP2, cultured onto mouse AVC cushions, or transplanted into the AVC of embryonic mouse hearts, underwent endothelial-to-mesenchymal transition and expressed markers of valve interstitial cells of different valvular layers demonstrating tissue functionality. HPVCs also differentiated into tendinous/chondrogenic cells in line with the valvular repertoire. Extending this valvulogenic model to patient specific iPS cells, we recapitulated features of mitral valve prolapse and uncovered that dysregulation of the SHH pathway is likely to be at the origin of the disease thus providing a putative therapeutic target.\n\nHuman pluripotent stem cells recapitulate early valvulogenesis and provide a powerful model to systematically decipher the origin and lineage contribution of different valvular cell types in humans as well as to study valve diseases in a dish.

developmental biology↗

bioRxiv2018

Myocardial Notch-Rbpj deletion does not affect heart development or function

During vertebrate cardiac development NOTCH signaling activity in the endocardium is essential for the crosstalk between endocardium and myocardium that initiates ventricular trabeculation and valve primordium formation. This crosstalk leads later to the maturation and compaction of the ventricular chambers and the morphogenesis of the cardiac valves, and its alteration may lead to disease. Although endocardial NOTCH signaling has been shown to be crucial for heart development, its physiological role in the myocardium has not been clearly established. Here we have used a genetic strategy to evaluate the role of NOTCH in myocardial development. We have inactivated the unique and ubiquitous NOTCH effector RBPJ in the early cardiomyocytes progenitors, and examined its consequences in cardiac development and function. Our results demonstrate that mice with cTnT-Cre-mediated myocardial-specific deletion of Rbpj develop to term, with homozygous mutant animals showing normal expression of cardiac development markers, and normal adult heart function. Similar observations have been obtained after Notch1 deletion with cTnT-Cre. We have also deleted Rbpj in both myocardial and endocardial progenitor cells, using the Nkx2.5-Cre driver, resulting in ventricular septal defect (VSD), double outlet right ventricle (DORV), and bicuspid aortic valve (BAV), due to NOTCH signaling abrogation in the endocardium of cardiac valves territories. Our data demonstrate that NOTCH-RBPJ inactivation in the myocardium does not affect heart development or adult cardiac function.

developmental biology↗