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The Drosophila Transcription Factors Tinman and Pannier Activate and Collaborate with Myocyte Enhancer Factor-2 to Promote Heart Cell Fate.

Lovato TL, Sensibaugh CA, Swingle KL, Martinez MM, Cripps RM - PLoS ONE (2015)

Bottom Line: We found that mesodermal over-expression of Tinman and Pannier resulted in approximately 20% of embryos with ectopic Hand and Sulphonylurea receptor (Sur) expression.By adding MEF2 alongside Tinman and Pannier, a dramatic expansion in the expression of Hand and Sur was observed in almost all embryos analyzed.Two additional cardiac markers were also expanded in their expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of New Mexico, Albuquerque, NM 87131-1091, United States of America.

ABSTRACT
Expression of the MADS domain transcription factor Myocyte Enhancer Factor 2 (MEF2) is regulated by numerous and overlapping enhancers which tightly control its transcription in the mesoderm. To understand how Mef2 expression is controlled in the heart, we identified a late stage Mef2 cardiac enhancer that is active in all heart cells beginning at stage 14 of embryonic development. This enhancer is regulated by the NK-homeodomain transcription factor Tinman, and the GATA transcription factor Pannier through both direct and indirect interactions with the enhancer. Since Tinman, Pannier and MEF2 are evolutionarily conserved from Drosophila to vertebrates, and since their vertebrate homologs can convert mouse fibroblast cells to cardiomyocytes in different activator cocktails, we tested whether over-expression of these three factors in vivo could ectopically activate known cardiac marker genes. We found that mesodermal over-expression of Tinman and Pannier resulted in approximately 20% of embryos with ectopic Hand and Sulphonylurea receptor (Sur) expression. By adding MEF2 alongside Tinman and Pannier, a dramatic expansion in the expression of Hand and Sur was observed in almost all embryos analyzed. Two additional cardiac markers were also expanded in their expression. Our results demonstrate the ability to initiate ectopic cardiac fate in vivo by the combination of only three members of the conserved Drosophila cardiac transcription network, and provide an opportunity for this genetic model system to be used to dissect the mechanisms of cardiac specification.

No MeSH data available.


Related in: MedlinePlus

Pericardin and H15 are activated by the over-expression of tinman, pannier and Mef2 in the mesoderm.(A,C and E) Control embryos. (B,D and F): 24B+twi>tin+pnr+Mef2 embryos. (A,B) Antibody stain against Fasciclin III which marks the visceral mesoderm at stage 10. (C,D) Antibody stain against Pericardin which marks the pericardial cells. (E,F) Antibody stain against H15 which is a cardiac-specific T box transcription factor. Arrows point to normal expression and arrowheads point to expanded expression. Bar, 100μm.
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pone.0132965.g006: Pericardin and H15 are activated by the over-expression of tinman, pannier and Mef2 in the mesoderm.(A,C and E) Control embryos. (B,D and F): 24B+twi>tin+pnr+Mef2 embryos. (A,B) Antibody stain against Fasciclin III which marks the visceral mesoderm at stage 10. (C,D) Antibody stain against Pericardin which marks the pericardial cells. (E,F) Antibody stain against H15 which is a cardiac-specific T box transcription factor. Arrows point to normal expression and arrowheads point to expanded expression. Bar, 100μm.

Mentions: We next investigated the effect upon marker gene expression of adding a third factor used in vertebrate conversion experiments, namely MEF2. With the addition of MEF2 to embryos over-expressing Tin and Pnr, the patterns of Hand and Sur transcripts were dramatically expanded in 100% of embryos analyzed, in a thickening expanse of cells adjacent to where the cardiac tube lies, as well as elsewhere in the mesoderm (Fig 5E and 5F). We also wanted to determine if visceral mesoderm fate was also being expanded in these embryos, since Tin is required for visceral mesoderm specification [43]. To do this, we used an antibody against Fasciclin III, which is expressed in the visceral mesoderm precursors at early embryonic stages. At stage 10, there was a slight expansion of FasIII expression compared to controls (Fig 6A and 6B), however this expansion did not persist into later stages (data not shown). We conclude that the predominant activation of cell fate in these embryos is the activation of cardiac fate.


The Drosophila Transcription Factors Tinman and Pannier Activate and Collaborate with Myocyte Enhancer Factor-2 to Promote Heart Cell Fate.

Lovato TL, Sensibaugh CA, Swingle KL, Martinez MM, Cripps RM - PLoS ONE (2015)

Pericardin and H15 are activated by the over-expression of tinman, pannier and Mef2 in the mesoderm.(A,C and E) Control embryos. (B,D and F): 24B+twi>tin+pnr+Mef2 embryos. (A,B) Antibody stain against Fasciclin III which marks the visceral mesoderm at stage 10. (C,D) Antibody stain against Pericardin which marks the pericardial cells. (E,F) Antibody stain against H15 which is a cardiac-specific T box transcription factor. Arrows point to normal expression and arrowheads point to expanded expression. Bar, 100μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4520567&req=5

pone.0132965.g006: Pericardin and H15 are activated by the over-expression of tinman, pannier and Mef2 in the mesoderm.(A,C and E) Control embryos. (B,D and F): 24B+twi>tin+pnr+Mef2 embryos. (A,B) Antibody stain against Fasciclin III which marks the visceral mesoderm at stage 10. (C,D) Antibody stain against Pericardin which marks the pericardial cells. (E,F) Antibody stain against H15 which is a cardiac-specific T box transcription factor. Arrows point to normal expression and arrowheads point to expanded expression. Bar, 100μm.
Mentions: We next investigated the effect upon marker gene expression of adding a third factor used in vertebrate conversion experiments, namely MEF2. With the addition of MEF2 to embryos over-expressing Tin and Pnr, the patterns of Hand and Sur transcripts were dramatically expanded in 100% of embryos analyzed, in a thickening expanse of cells adjacent to where the cardiac tube lies, as well as elsewhere in the mesoderm (Fig 5E and 5F). We also wanted to determine if visceral mesoderm fate was also being expanded in these embryos, since Tin is required for visceral mesoderm specification [43]. To do this, we used an antibody against Fasciclin III, which is expressed in the visceral mesoderm precursors at early embryonic stages. At stage 10, there was a slight expansion of FasIII expression compared to controls (Fig 6A and 6B), however this expansion did not persist into later stages (data not shown). We conclude that the predominant activation of cell fate in these embryos is the activation of cardiac fate.

Bottom Line: We found that mesodermal over-expression of Tinman and Pannier resulted in approximately 20% of embryos with ectopic Hand and Sulphonylurea receptor (Sur) expression.By adding MEF2 alongside Tinman and Pannier, a dramatic expansion in the expression of Hand and Sur was observed in almost all embryos analyzed.Two additional cardiac markers were also expanded in their expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of New Mexico, Albuquerque, NM 87131-1091, United States of America.

ABSTRACT
Expression of the MADS domain transcription factor Myocyte Enhancer Factor 2 (MEF2) is regulated by numerous and overlapping enhancers which tightly control its transcription in the mesoderm. To understand how Mef2 expression is controlled in the heart, we identified a late stage Mef2 cardiac enhancer that is active in all heart cells beginning at stage 14 of embryonic development. This enhancer is regulated by the NK-homeodomain transcription factor Tinman, and the GATA transcription factor Pannier through both direct and indirect interactions with the enhancer. Since Tinman, Pannier and MEF2 are evolutionarily conserved from Drosophila to vertebrates, and since their vertebrate homologs can convert mouse fibroblast cells to cardiomyocytes in different activator cocktails, we tested whether over-expression of these three factors in vivo could ectopically activate known cardiac marker genes. We found that mesodermal over-expression of Tinman and Pannier resulted in approximately 20% of embryos with ectopic Hand and Sulphonylurea receptor (Sur) expression. By adding MEF2 alongside Tinman and Pannier, a dramatic expansion in the expression of Hand and Sur was observed in almost all embryos analyzed. Two additional cardiac markers were also expanded in their expression. Our results demonstrate the ability to initiate ectopic cardiac fate in vivo by the combination of only three members of the conserved Drosophila cardiac transcription network, and provide an opportunity for this genetic model system to be used to dissect the mechanisms of cardiac specification.

No MeSH data available.


Related in: MedlinePlus