Pandur P et al. (2013), Islet1-expressing cardiac progenitor cells: a c...

XB-ART-46561

Dev Genes Evol 2013 Mar 01;2231-2:117-29. doi: 10.1007/s00427-012-0400-1.

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Islet1-expressing cardiac progenitor cells: a comparison across species.

Pandur P , Sirbu IO , Kühl SJ , Philipp M , Kühl M .

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Adult mammalian cardiac stem cells express the LIM-homeodomain transcription factor Islet1 (Isl1). They are considered remnants of Isl1-positive embryonic cardiac progenitor cells. During amniote heart development, Isl1-positive progenitor cells give rise mainly to the outflow tract, the right ventricle, and parts of the atria. This led to the hypothesis that the development of the right ventricle of the amniote heart depends on the recruitment of additional cells to the primary heart tube. The region from which these additional, Isl1-positive cells originate is called second heart field, as opposed to the first heart field whose cells form the primary heart tube. Here, we review the available data about Isl1 in different species, demonstrating that Isl1 is an important component of the core transcription factor network driving early cardiogenesis in animals of the two clades, deuterostomes, and protostomes. The data support the view of a single cardiac progenitor cell population that includes Isl1-expressing cells and which differentiates into the various cardiac lineages during embryonic development in vertebrates but not in other phyla of the animal kingdom.

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Species referenced: Xenopus
Genes referenced: atm fgf8 isl1 ltbp3 nkx2-5 shf shh tbl1x tbx2 tbx5

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	Fig. 1. The evolutionary relationship of the organisms discussed in this review and a schematic presentation of the gross morphology of their pumping organs. Ventricular chambers are depicted in red; atrial chambers are shown in blue. The atrium and ventricle in molluscs are colored in light blue and light red since it is not clear whether they are indeed homologous to their vertebrate counterparts. The dashed arrows indicate the appearance of Isl1-positive pharyngeal mesodermal cells in deuterostomes that contribute to the head musculature and, in craniata, to the heart. The phylogenetic tree is based on Simoes-Costa et al. (2005)
	Fig. 2. Illustration of the evolutionary relationship of Isl1 genes in different species. a The phylogenetic tree was generated using Clustal W (http://www.ebi.ac.uk/Tools/phylogeny/clustalw2_phylogeny/) (Chenna et al. 2003). Numbers indicate the genetic distance between the nodes of the tree. Sequences used were: NP_002193.2 (Homo sapiens), NP_067434.3 (M. musculus), NP_571037.1 (D. rerio), NP_990745.1 (G. gallus), NP_001104188.1 (X. laevis), AF226616_1 (Branchiostoma floridae), NP_001027767.1 (C. intestinalis), NP_476775.1 (D. melanogaster). b Comparison of Isl1 protein sequences. The percentages depict the degree of identical and similar (in parentheses) amino acids
	Fig. 3. A simplified schematic presentation of heart development in different species. a Mouse. Developmental stages are indicated in embryonic days (E). The cartoons show a dorsal view of a flattened embryo (E6.5), an anterior view (E7.5), and a lateral view (E8.0). Additionally, a schematic illustration of a transverse section at E8.0 is provided. The SHF is characterized by the presence of Isl1-positive cells and is indicated in red. bX. laevis. Developmental stages are according to Nieuwkoop and Faber (1975). The cartoons show an anterior view (st.13), a ventral view (st.24), and a lateral view (st.31). Additionally, a schematic illustration of a transverse section through the heart at st.31 is provided. At st.24, cells of the SHF (red) express isl1 whereas cells of the FHF (blue) are positive for tbx5. cD. rerio. Developmental stages are indicated in hours post-fertilization (hpf). The cartoons show a lateral view for stage 5 hpf and dorsal views for stages 12.5, 20, and 30 hpf with the anterior side up. The localization of early cardiac progenitor cells at 40 % epiboly, as well as the distinction between an atrial and a ventricular fate was analyzed by fate-mapping experiments. An Isl1-positive cell population that contributes to the arterial pole is located posterior and dorsal to the ventricle and is indicated in red. It only partially contributes to the heart. The zebrafish SHF is characterized by the expression of ltbp3. Of note, the arrangement of the atrium and ventricle along the anterior–posterior axis is inverted at later stages (not shown here). As a result, the atrium will come to lie posterior to the ventricle. CPC: common cardiac progenitor cell population, A: anterior, D: dorsal, P: posterior, V: ventral, FHF: first heart field; SHF: second heart field, PHT: primary heart tube. Partly adopted from Gessert and Kühl (2009)
	Fig. 4. Early heart development in C. intestinalis. The heart derives from the bilateral B7.5 blastomeres indicated in red. TVC: trunk ventral cells, ATM: anterior tail muscles. Adopted from Stolfi et al. (2010)
	Fig. 5. Gene regulatory networks in cardiac cells including Isl1. a Interaction of key cardiac transcription factors in the early cardiac mesoderm in Drosophila. doc: dorsocross, tup: tailup, pnr: pannier, tin: Tinman. b Interaction of signaling molecules and transcription factors including Isl1 in the pharyngeal mesoderm/SHF in the mouse. Shh: sonic hedgehog, RA: retinoic acid, Fgf8: fibroblast growth factor 8

References [+] :

Abu-Issa, Heart field: from mesoderm to heart tube. 2007, Pubmed