Hand is a direct target of Tinman and GATA factors during Drosophila cardiogenesis and hematopoiesis

Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA.
Development (Impact Factor: 6.46). 09/2005; 132(15):3525-36. DOI: 10.1242/dev.01899
Source: PubMed

ABSTRACT The existence of hemangioblasts, which serve as common progenitors for hematopoietic cells and cardioblasts, has suggested a molecular link between cardiogenesis and hematopoiesis in Drosophila. However, the molecular mediators that might link hematopoiesis and cardiogenesis remain unknown. Here, we show that the highly conserved basic helix-loop-helix (bHLH) transcription factor Hand is expressed in cardioblasts, pericardial nephrocytes and hematopoietic progenitors. The homeodomain protein Tinman and the GATA factors Pannier and Serpent directly activate Hand in these cell types through a minimal enhancer, which is necessary and sufficient to drive Hand expression in these different cell types. Hand is activated by Tinman and Pannier in cardioblasts and pericardial nephrocytes, and by Serpent in hematopoietic progenitors in the lymph gland. These findings place Hand at a nexus of the transcriptional networks that govern cardiogenesis and hematopoiesis, and indicate that the transcriptional pathways involved in development of the cardiovascular, excretory and hematopoietic systems may be more closely related than previously appreciated.

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    • "The following mutant Drosophila melanogaster strains were used for mapping and characterization of the reported EMS alleles: Cg25C DTS-L3 and Cg25C b-9 ([30], gift from M. Mink, University of Szeged), LanA 9–32 ([98], gift from T. Volk, Weizmann Institute of Science), P{lacW}Cg25C k00405 , P{SUPor-P}LanB1 KG03456 , Mi{MIC}LanA MI02491 , Mi{ET1}LanA MB01129 , Mi{MIC}LanB2 MI03747 , Mi{ET1}prc MB03017 , P{PZ}vkg 01209 , P{PZ}wb 09437 , Df(2L)BSC110, Df(2L)BSC172, Df(2L)Exel7022, Df(2L)BSC233, Df(2L)ED12527 and about 180 additional deficiencies spanning chromosome 2 (all available from the Bloomington Stock Center at Indiana University, USA). For phenotypic analysis we used these additional reporter lines: Hand-GFP on chromosome 3 (HCH-GFP; [51]), Mhc-tau::GFP on chromosome X ([99]; obtained from F. Schnorrer, Max-Planck-Institute of Biochemistry) and the Flytrap GFP lines vkg G454 (vkg::GFP) and trol ZCL1973 (trol::GFP) ([58,59,100], obtained from L. Cooley, Yale University Medical School). For the analysis of pericardial cells in the absence of alary muscles, mutants of the desired allele were combined with the X-chromosomal mutation org-1 OJ487 [18] and crossed with males of the corresponding single mutant allele carrying Hand-GFP. "
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    ABSTRACT: Background The Drosophila heart (dorsal vessel) is a relatively simple tubular organ that serves as a model for several aspects of cardiogenesis. Cardiac morphogenesis, proper heart function and stability require structural components whose identity and ways of assembly are only partially understood. Structural components are also needed to connect the myocardial tube with neighboring cells such as pericardial cells and specialized muscle fibers, the so-called alary muscles. Results Using an EMS mutagenesis screen for cardiac and muscular abnormalities in Drosophila embryos we obtained multiple mutants for two genetically interacting complementation groups that showed similar alary muscle and pericardial cell detachment phenotypes. The molecular lesions underlying these defects were identified as domain-specific point mutations in LamininB1 and Cg25C, encoding the extracellular matrix (ECM) components laminin β and collagen IV α1, respectively. Of particular interest within the LamininB1 group are certain hypomorphic mutants that feature prominent defects in cardiac morphogenesis and cardiac ECM layer formation, but in contrast to amorphic mutants, only mild defects in other tissues. All of these alleles carry clustered missense mutations in the laminin LN domain. The identified Cg25C mutants display weaker and largely temperature-sensitive phenotypes that result from glycine substitutions in different Gly-X-Y repeats of the triple helix-forming domain. While initial basement membrane assembly is not abolished in Cg25C mutants, incorporation of perlecan is impaired and intracellular accumulation of perlecan as well as the collagen IV α2 chain is detected during late embryogenesis. Conclusions Assembly of the cardiac ECM depends primarily on laminin, whereas collagen IV is needed for stabilization. Our data underscore the importance of a correctly assembled ECM particularly for the development of cardiac tissues and their lateral connections. The mutational analysis suggests that the β6/β3/β8 interface of the laminin β LN domain is highly critical for formation of contiguous cardiac ECM layers. Certain mutations in the collagen IV triple helix-forming domain may exert a semi-dominant effect leading to an overall weakening of ECM structures as well as intracellular accumulation of collagen and other molecules, thus paralleling observations made in other organisms and in connection with collagen-related diseases.
    BMC Developmental Biology 06/2014; 14(1):26. DOI:10.1186/1471-213X-14-26 · 2.67 Impact Factor
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    • "In addition, we reasoned that the overexpression of the processed intracellular domain of Notch (Nicd), which has been shown to convert the Su(H) complex from a repressor into an activator for target genes (Bray and Furriols, 2001; Bray and Bernard, 2010), should induce ectopic activity of the Him gene in CCs. In agreement with this prediction, overexpression of Nicd in all cardiac progenitors by the Hand-Gal4 driver (Han and Olson, 2005) induced ectopic expression of Him, which is normally restricted to PCs, in Mef2-expressing CCs (Fig. 7D,E). The disorganized heart cells and the very weak expression of Mef2 in CCs suggest that CC cell fate specification is highly abnormal in Hand>Nicd embryos, with the CCs in the process of being partly transformed to PCs. "
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    ABSTRACT: The Drosophila heart is composed of two distinct cell types, the contractile cardial cells (CCs) and the surrounding non-muscle pericardial cells (PCs), development of which is regulated by a network of conserved signaling molecules and transcription factors (TFs). Here, we used machine learning with array-based chromatin immunoprecipitation (ChIP) data and TF sequence motifs to computationally classify cell type-specific cardiac enhancers. Extensive testing of predicted enhancers at single-cell resolution revealed the added value of ChIP data for modeling cell type-specific activities. Furthermore, clustering the top-scoring classifier sequence features identified novel cardiac and cell type-specific regulatory motifs. For example, we found that the Myb motif learned by the classifier is crucial for CC activity, and the Myb TF acts in concert with two forkhead domain TFs and Polo kinase to regulate cardiac progenitor cell divisions. In addition, differential motif enrichment and cis-trans genetic studies revealed that the Notch signaling pathway TF Suppressor of Hairless [Su(H)] discriminates PC from CC enhancer activities. Collectively, these studies elucidate molecular pathways used in the regulatory decisions for proliferation and differentiation of cardiac progenitor cells, implicate Su(H) in regulating cell fate decisions of these progenitors, and document the utility of enhancer modeling in uncovering developmental regulatory subnetworks.
    Development 02/2014; 141(4):878-88. DOI:10.1242/dev.101709 · 6.46 Impact Factor
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    • "Thus, severely compromised integrin/ ILK pathway function is detrimental for the heart, but fine-tuned moderate reduction maintains youthful cardiac performance, suggesting a dual role for this complex in regulating cardiac integrity and aging. Results ilk heterozygous mutants have extended lifespan in Drosophila As the RNAi-mediated KD of ilk extends lifespan in C. elegans (Hansen et al., 2005; Curran & Ruvkun, 2007; Kumsta et al., 2014), we wondered whether reduced ilk expression is also beneficial to longevity in Drosophila. As lifespan can be significantly modulated by genetic background (Grandison et al., 2009), we first backcrossed ilk 54 mutants (premature stop codon; Zervas et al., 2011 "
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    ABSTRACT: Cardiac performance decreases with age, which is a major risk factor for cardiovascular disease and mortality in the aging human population, but the molecular mechanisms underlying cardiac aging are still poorly understood. Investigating the role of integrin-linked kinase (ilk) and β1-integrin (myospheroid, mys) in Drosophila, which colocalize near cardiomyocyte contacts and Z-bands, we find that reduced ilk or mys function prevents the typical changes of cardiac aging seen in wildtype, such as arrhythmias. In particular, the characteristic increase in cardiac arrhythmias with age is prevented in ilk and mys heterozygous flies with nearly identical genetic background, and they live longer, in line with previous findings in Caenorhabditis elegans for ilk and in Drosophila for mys. Consistent with these findings, we observed elevated β1-integrin protein levels in old compared with young wild-type flies, and cardiac-specific overexpression of mys in young flies causes aging-like heart dysfunction. Moreover, moderate cardiac-specific knockdown of integrin-linked kinase (ILK)/integrin pathway-associated genes also prevented the decline in cardiac performance with age. In contrast, strong cardiac knockdown of ilk or ILK-associated genes can severely compromise cardiac integrity, including cardiomyocyte adhesion and overall heart function. These data suggest that ilk/mys function is necessary for establishing and maintaining normal heart structure and function, and appropriate fine-tuning of this pathway can retard the age-dependent decline in cardiac performance and extend lifespan. Thus, ILK/integrin-associated signaling emerges as an important and conserved genetic mechanism in longevity, and as a new means to improve age-dependent cardiac performance, in addition to its vital role in maintaining cardiac integrity.
    Aging cell 01/2014; 13(3). DOI:10.1111/acel.12193 · 6.34 Impact Factor
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