Islet1 Derivatives in the Heart Are of Both Neural Crest and Second Heart Field Origin

Department of Cell and Developmental Biology, Cardiovascular Institute and Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA.
Circulation Research (Impact Factor: 11.02). 03/2012; 110(7):922-6. DOI: 10.1161/CIRCRESAHA.112.266510
Source: PubMed


Islet1 (Isl1) has been proposed as a marker of cardiac progenitor cells derived from the second heart field and is utilized to identify and purify cardiac progenitors from murine and human specimens for ex vivo expansion. The use of Isl1 as a specific second heart field marker is dependent on its exclusion from other cardiac lineages such as neural crest.
Determine whether Isl1 is expressed by cardiac neural crest.
We used an intersectional fate-mapping system using the RC::FrePe allele, which reports dual Flpe and Cre recombination. Combining Isl1(Cre/+), a SHF driver, and Wnt1::Flpe, a neural crest driver, with Rc::FrePe reveals that some Isl1 derivatives in the cardiac outflow tract derive from Wnt1-expressing neural crest progenitors. In contrast, no overlap was observed between Wnt1-derived neural crest and an alternative second heart field driver, Mef2c-AHF-Cre.
Isl1 is not restricted to second heart field progenitors in the developing heart but also labels cardiac neural crest. The intersection of Isl1 and Wnt1 lineages within the heart provides a caveat to using Isl1 as an exclusive second heart field cardiac progenitor marker and suggests that some Isl1-expressing progenitor cells derived from embryos, embryonic stem cultures, or induced pluripotent stem cultures may be of neural crest lineage.

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    • "RESULTS Deletion of Pten in the SHF progenitors results in SHF expansion and enlarged size of SHF derivatives Mef2c-AHF-Cre (hereafter referred to as Mef2c-Cre) mice express the Cre recombinase in the anterior heart field (AHF), a subset of the SHF which gives rise to OFT/RV (Verzi et al., 2005). This Cre line has been extensively utilized to delete genes for investigation of the SHF development in mice (Ai et al., 2007; Bai et al., 2013; Engleka et al., 2012; Xie et al., 2012). Using Mef2c-Cre, Pten was deleted in the SHF. "
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    ABSTRACT: Second heart field (SHF) progenitors exhibit continued proliferation and delayed differentiation, which are modulated by FGF4/8/10, BMP and canonical Wnt/β-catenin signaling. PTEN-Akt signaling regulates the stem cell/progenitor cell homeostasis in several systems, such as hematopoietic stem cells, intestinal stem cells and neural progenitor cells. To address whether PTEN-Akt signaling is involved in regulating cardiac progenitors, we deleted Pten in SHF progenitors. Deletion of Pten caused SHF expansion and increased the size of the SHF derivatives, the right ventricle and the outflow tract. Cell proliferation of cardiac progenitors was enhanced, whereas cardiac differentiation was unaffected by Pten deletion. Removal of Akt1 rescued the phenotype and early lethality of Pten deletion mice, suggesting that Akt1 was the key downstream target that was negatively regulated by PTEN in cardiac progenitors. Furthermore, we found that inhibition of FOXO by Akt1 suppressed the expression of the gene encoding the BMP ligand (BMP7), leading to dampened BMP signaling in the hearts of Pten deletion mice. Cardiac activation of Akt also increased the Ser552 phosphorylation of β-catenin, thus enhancing its activity. Reducing β-catenin levels could partially rescue heart defects of Pten deletion mice. We conclude that Akt signaling regulates the cell proliferation of SHF progenitors through coordination of BMP signaling and β-catenin activity. © 2015. Published by The Company of Biologists Ltd.
    Development 02/2015; 142(4):732-42. DOI:10.1242/dev.119016 · 6.46 Impact Factor
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    • "In the regions of the heart, the cNCC contribute mesenchyme for the septation of the outflow tract, the morphogenesis of the great arteries, and the maturation of the atrioventricular valves and the conduction system (Kirby and Hutson, 2010; Keyte and Hutson, 2012). Abnormal development of these structures, secondary to a loss of cNCC, has been postulated to represent a significant proportion of congenital heart defects (Porras and Brown, 2008; Rentschler et al., 2010; Engleka et al., 2012), thus the identification of factors that influence cNCC migration and development is of significant interest. In this study, we used primary cultures of cardiac NCC to test the hypothesis that a deficit of Zn can result in impaired NCC viability and function, and thus potentially contribute to the type of heart anomalies that have been observed in fetuses obtained from Zn-deficient animals. "
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    ABSTRACT: BACKGROUND Developmental zinc (Zn) deficiency increases the incidence of heart anomalies in rat fetuses, in regions and structures derived from the outflow tract. Given that the development of the outflow tract requires the presence of cardiac neural crest cells (cNCC), we speculated that Zn deficiency selectively kills cNCC and could lead to heart malformations.METHODS Cardiac NCC were isolated from E10.5 rat embryos and cultured in control media (CTRL), media containing 3 μM of the cell permeable metal chelator N, N, N′, N′-tetrakis (2-pyridylmethyl) ethylene diamine (TPEN), or in TPEN-treated media supplemented with 3 μM Zn (TPEN + Zn). Cardiac NCC were collected after 6, 8, and 24 h of treatment to assess cell viability, proliferation, and apoptosis.RESULTSThe addition of TPEN to the culture media reduced free intracellular Zn pools and cell viability as assessed by low ATP production, compared to cells grown in control or Zn-supplemented media. There was an accumulation of reactive oxygen species, a release of mitochondrial cytochrome c into the cytoplasm, and an increased cellular expression of active caspase-3 in TPEN-treated cNCC compared to cNCC cultured in CTRL or TPEN + Zn media.CONCLUSION Zn deficiency can result in oxidative stress in cNCC, and subsequent decreases in their population and metabolic activity. These data support the concept that Zn deficiency associated developmental heart defects may arise in part as a consequence of altered cNCC metabolism
    Birth Defects Research Part B Developmental and Reproductive Toxicology 02/2015; 104(1). DOI:10.1002/bdrb.21135 · 0.77 Impact Factor
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    • "The subpopulations of IRX4 þ /TBX5 þ or IRX4 þ /ISLET1 þ cells, identified in this study using an antibody staining approach, suggest that the IRX4 þ cells of the crescent potentially encompass two distinct progenitor populations. Because Irx4 is expressed in both ventricular chambers , while Tbx5 or Islet1 expression is restricted to the left and right ventricle , respectively, it is reasonable to hypothesize that Irx4 labels two distinct ventricular progenitors in the cardiac crescent (Domian et al., 2009; Herrmann et al., 2011; Engleka et al., 2012). The identification of putative left and right ventricular progenitors is important for understanding the cellular dynamics responsible for the allocation of cells to distinct ventricular chambers. "
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    ABSTRACT: Background: The ventricular myocardium is the most prominent layer of the heart, and the most important for mediating cardiac physiology. Although the ventricular myocardium is critical for heart function, the cellular hierarchy responsible for ventricle-specific myocardium development remains unresolved. Results: To determine the pattern and time course of ventricular myocardium development, we investigated IRX4 protein expression, which has not been previously reported. We identified IRX4+ cells in the cardiac crescent, and these cells were positive for markers of the first or second heart fields. From the onset of chamber formation, IRX4+ cells were restricted to the ventricular myocardium. This expression pattern persisted into adulthood. Of interest, we observed that IRX4 exhibits developmentally regulated dynamic intracellular localization. Throughout prenatal cardiogenesis, and up to postnatal day 4, IRX4 was detected in the cytoplasm of ventricular myocytes. However, between postnatal days 5–6, IRX4 translocated to the nucleus of ventricular myocytes. Conclusions: Given the ventricle-specific expression of Irx4 in later stages of heart development, we hypothesize that IRX4+ cells in the cardiac crescent represent the earliest cell population in the cellular hierarchy underlying ventricular myocardium development.
    Developmental Dynamics 03/2014; 243(3):C1. DOI:10.1002/dvdy.24045 · 2.38 Impact Factor
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