Posts in Category: Development

Cardiac Regeneration: Lessons From Development

 

Cardiac Regeneration: Lessons From Development

Francisco X. Galdos, Yuxuan Guo, Sharon L. Paige, Nathan J. VanDusen, Sean M. Wu, William T. Pu

Model of the trabeculation process. During trabeulation, a small fraction of cardiomyocytes (CMs) in the compact myocardium (pink) are first specified as trabeculating CMs (brown). These cells delaminate from the compact myocardium and migrate inward to form the first trabecular CMs. CMs in both compacted and trabecular myocardium further proliferate. This proliferation, together with CM migration and rearrangement, results in protrusion and expansion of the trabecular myocardium (illustration credit: Ben Smith). [Powerpoint File]

Cardiac Regeneration: Lessons From Development

Cardiac Regeneration: Lessons From Development

Francisco X. Galdos, Yuxuan Guo, Sharon L. Paige, Nathan J. VanDusen, Sean M. Wu, William T. Pu

Regulation of cardiac progenitor proliferation and differentiation. A, Schematic showing the anterolateral position of first heart field (FHF) progenitors and dorsomedial position of second heart field (SHF) progenitors at embryonic day (E) 7.5. Canonical wingless-type MMTV integration site family member (WNTs), Sonic Hedgehog (SHH), and fibroblast growth factors (FGFs) are expressed dorsally in the region encompassed by the SHF, whereas noncanonical WNTs, BMP2, and FGF8 are expressed ventrally, where the FHF is present. FHF progenitors make up the cardiac crescent and differentiate before the SHF to form the developing heart tube at E8.0. SHF maintains their proliferative state and elongate the heart tube by migrating and differentiating at the inflow and outflow poles of the heart. B, Noncanonical WNTs, BMP2/4, and FGF8 signaling drives FHF progenitors to differentiates toward the myocyte lineage. Meanwhile, canonical WNT/β-catenin, SHH, and FGFs maintain SHF progenitor proliferation. SHF progenitor migration to the outflow and inflow poles of the heart tube exposes them to BMP2/4 and noncanonical WNTs, which drives SHF progenitors to exit their proliferative state and differentiate. C, Canonical WNT/ β-catenin signaling inhibits the differentiation of cardiac progenitors to the myocytes. BMP signaling activates SMAD4 that binds to the transcription factor HOPX to directly inhibit canonical WNT/β-catenin. Moreover, noncanonical WNTs such as WNT5a and WNT11 also inhibit canonical WNT/β-catenin to drive cardiac progenitor differentiation (illustration credit: Ben Smith). [Powerpoint File]

Cardiac Regeneration: Lessons From Development

Cardiac Regeneration: Lessons From Development

Francisco X. Galdos, Yuxuan Guo, Sharon L. Paige, Nathan J. VanDusen, Sean M. Wu, William T. Pu

Specification of mesodermal precursors. Schematic representing the signaling events leading to mesodermal specification during early development. NODAL (nodal growth differentiation factor) is first expressed proximally at embryonic day (E) 5.0. Through an autoregulatory loop, NODAL activates its own expression throughout the epiblast (shown in light purple) and goes on to induce the expression of NODAL antagonists, LEFTY1 and CER1, in the distal visceral endoderm at E5.5 (DVE). The DVE migrates anteriorly where it specifies the anterior portion of the embryo as shown in the yellow hues at E6.5 to 7.5. The anterior visceral endoderm (AVE, yellow) limits NODAL signaling to the posterior of the embryo. Along with wingless-type MMTV integration site family member 3 (WNT3) and bone morphogenic protein (BMP) signaling, NODAL specifies early primitive streak progenitors to the mesoderm fate. [Powerpoint File]

Endocardial Notch Signaling in Cardiac Development and Disease

Endocardial Notch Signaling in Cardiac Development and Disease

Guillermo Luxán*, Gaetano D’Amato*, Donal MacGrogan*, José Luis de la Pompa

The Notch signaling pathway. In the signaling cell, membrane-bound Notch ligands (Dll1, 3, 4, and Jag1, 2) are characterized by a Delta/Serrate/Lag2 motif (light yellow) located in the extracellular domain. Ligand activity is regulated by the ubiquitin ligase Mind bomb-1 (Mib1) through ubiquitinylation of the intracellular domain (dark yellow squares). In the signal-receiving cell, the Notch receptor (Notch 1–4) is processed at the S1 site by a furin protease, sugar-modified by Fringe in the Golgi and is thought to be inserted into the membrane as a heterodimer with a large extracellular domain (NECD). Ligand–receptor interaction leads to 2 consecutive cleavage events (at S2 and S3 sites, respectively) performed by an ADAM (A Disintegrin And Metalloprotease-containing) protease and presenilin, which release the Notch intracellular domain (NICD) that translocates to the nucleus and binds to CSL (CBF1, Suppressor of Hairless, Lag-1). In the absence of NICD, CSL associates with corepressor proteins (Co-R) and histone deacetylases to repress transcription. After NICD binds to CSL, conformational changes occurring in CSL displace transcriptional repressors. The transcriptional coactivator Mastermind (MAML) is then able to bind to NICD/CSL to form a ternary complex that recruits additional coactivators (Co-A) to activate transcription of a set of target genes. [Powerpoint File]

Endocardial Notch Signaling in Cardiac Development and Disease

Endocardial Notch Signaling in Cardiac Development and Disease

Guillermo Luxán*, Gaetano D’Amato*, Donal MacGrogan*, José Luis de la Pompa

Key events in cardiac development. A, At human embryonic day 14 (hE14) or mouse E7.0. In the gastrulating embryo cardiac progenitors (purple) migrate into the anterior half of the primitive streak to reach the head folds. At E7.5, progenitor cell populations of the first and second heart fields (FHF, purple; SHF, yellow) have fused in the midline of the embryo. At E8.0, the heart tube stage, the approximate contributions of FHF and SHF are shown. B, The heart tube has an outer myocardial layer (light brown) and an inner endocardial endothelium (red) separated by cardiac jelly (gray). C and D, At E9.0, the heart is elongated and looping rightward (C). At E9.5, formation of the atrioventricular canal (AVC) separates the 2 chambers’ territories, the developing atria and ventricles (C). Formation of the valve primordia occurs around E10, together with ventricular chamber development that begins with trabeculae formation in the developing left and right ventricles, and epicardial formation from the proepicardium, located in the venous pole of the heart (D). E, Outflow tract (OFT) and aortic arch arteries (AAA) remodeling is dependent on the cardiac neural crest (CNC) cells. The OFT region of the heart initially exists as a single outflow vessel, which circulates blood into three major pairs of AAAs to join 2 paired dorsal aortae that distribute the blood throughout the embryo. Left, Neural crest cells migrate from the dorsal neural tube, surrounding the aortic arch arteries to the cardiac outflow Middle, The neural crest cells that invest the endothelial tubes of the AAAs differentiate into vascular smooth muscle cells. Right, the AAAs remodel to form the mature aortic arch, with neural crest–derived vascular smooth muscle cells contributing to most of the aortic arch and its major branches. F, Contribution of neural crest (purple) and epicardial (blue)–derived cells (NCDC and EPDC) to the cardiac valves. NCDCs migrate through the pharyngeal arches and into the OFT to initiate the reorganization of the OFT and formation of semilunar valves. EPDCs contribute to the formation of the coronary arteries, the interstitial cells in the myocardium, and the AV valves. In a top view of the septated heart, the relative contributions of NCDCs and EPDCs to cardiac valve leaflets and cusps are shown. G, E13.5-birth. The 4 chambers and valves are shown. The epicardium is shown in gray, and the coronary vessels in red and blue. H, Cushion fusion between E11.5 and E12.5 is a critical step in valve morphogenesis. Aberrant fusion events can lead to bicuspid aortic valve (BAV). R–NC and R–LC fusions might have different causes. I, Scheme depicting the thick ventricular walls of the normal adult heart and the thin and trabeculated walls of a noncompacted heart. In all panels, the ventral aspect of the heart is shown (anterior to the top). A indicates atria; la, left atrium, lv, left ventricle; LVNC, left ventricular noncompaction; mv, mitral valve; pv, pulmonary valve; rv, right ventricle; and tv, tricuspid valve. [Powerpoint File]

Endocardial Notch Signaling in Cardiac Development and Disease

Endocardial Notch Signaling in Cardiac Development and Disease

Guillermo Luxán*, Gaetano D’Amato*, Donal MacGrogan*, José Luis de la Pompa

Endocardial Notch signaling is essential for chamber development. A, Transverse section of an hematoxylin and eosin–stained WT E9.5 heart at the level the left ventricle (lv). The arrow points to a forming trabecula. B, The heart of a E9.5 RBPJk mutant embryo shows a collapsed endocardium (arrowhead) and poorly developed trabeculae (arrow). C, Scheme depicting Notch pathway elements expression the early ventricular myocardium: Mib1 is expressed throughout the endocardium (purple), Dll4 in endocardium at the base of the forming trabeculae (green), where Notch1 is activated (red), triggering signals involved in cardiomyocyte proliferation and differentiation. At this stage, the primitive myocardial epithelium begins to express compact myocardium markers. Images derived from Grego-Bessa et al.3 D, Episcopic 3-dimensional reconstruction of E16.5 WT and E, Mib1flox;cTnT-Cre hearts. Note the thick ventricular walls (brackets) and the small trabecular ridges (arrows) in the WT heart (D) and the thin compact myocardium and noncompacted trabecular in the mutant heart (E). *Disorganized interventricular septum. F, Schematic representation of Notch function during ventricular maturation and compaction. Mib1-Jag1 signaling from the myocardium (blue) activates Notch1 throughout the endocardium (red) to sustain trabecular patterning, maturation, and compaction. Proliferative compact myocardium is defined by the expression of Hey2, Tbx20, and n-myc, whereas the nonproliferative trabecular myocardium is defined by the expression of Anf, Bmp10, and Cx40. Images derived from Luxán et al.4 la indicates left atrium, ra, right atrial; and rv, right ventricle. [Powerpoint File]

Lncing Epigenetic Control of Transcription to Cardiovascular Development and Disease

Lncing Epigenetic Control of Transcription to Cardiovascular Development and Disease

Gizem Rizki, Laurie A. Boyer

Future directions for the study of long noncoding RNAs (lncRNAs) in cardiovascular biology. There still remain many unanswered questions about the exact functions and molecular mechanisms of lncRNAs that govern diverse aspects of cardiac physiology. Some of the outstanding questions and promising areas of research are outlined in the schematic. CM indicates cardiomyocyte (illustration credit: Ben Smith). [Powerpoint File]

Lncing Epigenetic Control of Transcription to Cardiovascular Development and Disease

Lncing Epigenetic Control of Transcription to Cardiovascular Development and Disease

Gizem Rizki, Laurie A. Boyer

Epigenetic regulation by cardiovascular long noncoding RNAs (lncRNAs). Mechanisms of action of lncRNAs, such as Bvht, Fendrr, and Mhrt, that regulate cardiac gene expression by modulating chromatin modifying protein complexes (A), and Kcnq-overlapping lncRNA 1 (Kcnq1ot1), which regulates chromatin organization and structure (B) are depicted. BAF indicates Brg1/Brm-associated factor; CM, cardiomyocyte; CP, cardiac progenitor cells; ESCs, embryonic stem cells; MES, mesodermal cells; PRC, polycomb repressive complex; and TrxG/MLL, trithorax/mixed lineage leukemia (illustration credit: Ben Smith). [Powerpoint File]

Lncing Epigenetic Control of Transcription to Cardiovascular Development and Disease

Lncing Epigenetic Control of Transcription to Cardiovascular Development and Disease

Gizem Rizki, Laurie A. Boyer

Long noncoding RNAs in the transcriptional circuitry of cardiovascular development. A, Many long noncoding RNAs (lncRNAs) are important for the development of different cell types in the cardiovascular system. Specific examples important for developmental transitions, such as Braveheart and Fendrr, as well as formation of cardiovascular cell types, such as Sencr and Malat1 are depicted. B, Transcriptional profiling studies have identified many lncRNAs that are differentially expressed during cardiac development. Many of these transcripts still await validation and further characterization (illustration credit: Ben Smith). [Powerpoint File]

Investigating the Transcriptional Control of Cardiovascular Development

Investigating the Transcriptional Control of Cardiovascular Development

Irfan S. Kathiriya*, Elphège P. Nora*, Benoit G. Bruneau

Studying cardiac regulatory elements. A, Left, Evolutionary constraints on some regulatory elements render them identifiable by comparative genomics, as exemplified by enhancers upstream of mouse Nkx2-5.86 Right, Combinations of specific chromatin features can reveal potential regulatory elements active in a given cell type. B, Left, Enhancer activity is classically tested by an ability of candidate elements to drive tissue- or stage-specific activity of a reporter. Middle, New technologies, such as SIF-seq,87 allow screening of large genomic neighborhoods for tissue-specific enhancers. Right, Genome Regulatory Organization Mapping with Integrated Transposons92 is a technology that can reveal integrated regulatory inputs exerted at a locus. [Powerpoint FIle]

Investigating the Transcriptional Control of Cardiovascular Development

Investigating the Transcriptional Control of Cardiovascular Development

Irfan S. Kathiriya*, Elphège P. Nora*, Benoit G. Bruneau

Molecular players for transcriptional regulation. A, Cis-regulatory elements containing DNA-binding sites are bound by transcription factors and (B) modulate the assembly of the preinitiation complex at promoters through (C) physical contacts driven by a 3-dimensional arrangement of chromatin, thereby acting as (D) a molecular platform between cellular signaling and gene activity. [Powerpoint File]

Molecular Regulation of Cardiomyocyte Differentiation

Molecular Regulation of Cardiomyocyte Differentiation

Sharon L. Paige, Karolina Plonowska, Adele Xu, Sean M. Wu

Regulation of cardiac mesoderm specification. Shown is a cross-section of an E7.5 mouse embryo detailing the signaling pathways that regulate cardiac specification within splanchnic mesoderm. Factors secreted by the adjacent endoderm that support cardiac mesoderm specification include fibroblast growth factor (FGF), bone morphogenetic protein (BMP), and sonic hedgehog (Shh). In addition, noncanonical Wnt ligands, such as Wnt11, expressed in splanchnic mesoderm also promote cardiac differentiation. Conversely, canonical Wnt ligands, including Wnt1, Wnt3a, and Wnt8, secreted from the overlying neuroectoderm, as well as BMP antagonists noggin and chordin secreted from the notochord inhibit cardiac mesoderm specification, thereby limiting the size of the cardiogenic fields. [Powerpoint File]

Molecular Regulation of Cardiomyocyte Differentiation

Molecular Regulation of Cardiomyocyte Differentiation

Sharon L. Paige, Karolina Plonowska, Adele Xu, Sean M. Wu

Schematic of cardiovascular lineage diversification. The specification of cardiomyocytes in the first heart field (FHF) and second heart field (SHF) is shown in the context of other cardiac cells that are also derived from a common cardiogenic mesoderm progenitor. In particular, Isl1 expression distinguishes the FHF and SHF. Comparison of action potentials for mature myocytes reveals the range of function generated from each heart field. *Developmental origin of the coronary endothelium is an active topic of investigation. Whereas some evidence points to partial contributions to the coronary endothelium from the epicardium,70,160 other sources, such as the endocardium161 and the sinus venosus,69 have also been reported. LV indicates left ventricle; and RV, right ventricle. [Powerpoint File]

Molecular Regulation of Cardiomyocyte Differentiation

Molecular Regulation of Cardiomyocyte Differentiation

Sharon L. Paige, Karolina Plonowska, Adele Xu, Sean M. Wu

Specification of chamber myocardium. The specification of cells to the chamber myocardium is modulated by Tbx5 and Tbx20 in tandem with more broadly expressed factors Nkx2-5 and Gata4. Tbx2 and Tbx3 suppress the expression of chamber myocardium–specific genes, resulting in low proliferation rate, slow conduction velocity, and poor contractibility characteristic to the primary myocardium. The primary myocardium phenotype becomes restricted to the atrioventricular canal (AVC) and proximal outflow tract (p-OFT). d-OFT indicates distal outflow tract; LA, left atrium; LV, left ventricle; and RV, right ventricle. [Powerpoint File]

Molecular Regulation of Cardiomyocyte Differentiation

Molecular Regulation of Cardiomyocyte Differentiation

Sharon L. Paige, Karolina Plonowska, Adele Xu, Sean M. Wu

Spatiotemporal regulation of trabeculation. The development of ventricular trabeculae is governed by signal transduction involving the endocardium, myocardium, and cardiac jelly. Pathways implicated in trabeculation are depicted in approximate chronological order of expression from left to right. Beginning with establishment of the cardiac jelly and endothelium, trabeculation progresses via cellular proliferation and migration and ends with degradation of the cardiac jelly. Factors involved in epigenetic mechanisms are underlined. BMP indicates bone morphogenetic protein; and VEGF, vascular endothelial growth factor. [Powerpoint File]