Article

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

ABSTRACT

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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    • "To test this hypothesis, we ablated Fn1 in the pharyngeal region using the Isl1 Cre knock-in strain of mice. In this strain, the Cre enzyme mediates recombination in several pharyngeal tissues including the pharyngeal and splanchnic mesoderm, endoderm, surface ectoderm and specific subpopulations of the cardiac neural crest (Cai et al., 2003; Engleka et al., 2012; Park et al., 2006). Our studies indicate that distinct, cell type-specific pharyngeal sources of Fn1 play a number of distinct, indispensible roles in cardiovascular development and the formation of the 4th pair of PAAs. "
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    ABSTRACT: Fibronectin (Fn1) is an evolutionarily conserved extracellular matrix glycoprotein essential for embryonic development. Global deletion of Fn1 leads to mid-gestation lethality from cardiovascular defects. However, severe morphogenetic defects that occur early in embryogenesis in these embryos precluded assigning a direct role for Fn1 in cardiovascular development. We noticed that Fn1 is expressed in strikingly non-uniform patterns during mouse embryogenesis, and that its expression is particularly enriched in the pharyngeal region corresponding with the pharyngeal arches 3, 4, and 6. This region bears a special importance for the developing cardiovascular system, and we hypothesized that the localized enrichment of Fn1 in the pharyngeal region may be essential for cardiovascular morphogenesis. To test this hypothesis, we ablated Fn1 using the Isl1(Cre) knock-in strain of mice. Deletion of Fn1 using the Isl1(Cre) strain resulted in defective formation of the 4th pharyngeal arch arteries (PAAs), aberrant development of the cardiac outflow tract (OFT), and ventricular septum defects. To determine the cell types responding to Fn1 signaling during cardiovascular development, we deleted a major Fn1 receptor, integrin α5 using the Isl1(Cre) strain, and observed the same spectrum of abnormalities seen in the Fn1 conditional mutants. Additional conditional mutagenesis studies designed to ablate integrin α5 in distinct cell types within the Isl1(+) tissues and their derivatives, suggested that the expression of integrin α5 in the pharyngeal arch mesoderm, endothelium, surface ectoderm and the neural crest were not required for PAA formation. Our studies suggest that an (as yet unknown) integrin α5-dependent signal extrinsic to the pharyngeal endothelium mediates the formation of the 4th PAAs.
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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.
    Full-text · Article · Feb 2015 · Development
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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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