title: MEF2D deficiency in neonatal cardiomyocytes triggers cell cycle re-entry and programmed cell death in vitro.
abstract: The cardiomyocyte cell cycle is a poorly understood process. Mammalian cardiomyocytes permanently withdraw from the cell cycle shortly after birth but can re-enter the cell cycle and proliferate when subjected to injury within a brief temporal window in the neonatal period. Thus, investigating the mechanisms of cell cycle regulation in neonatal cardiomyocytes may provide critical insight into the molecular events that prevent adult myocytes from proliferating in response to injury or stress. MEF2D is a key transcriptional mediator of pathological remodeling in the adult heart downstream of various stress-promoting insults. However, the specific gene programs regulated by MEF2D in cardiomyocytes are unknown. By performing genome-wide transcriptome analysis using MEF2D-depleted neonatal cardiomyocytes, we found a significant impairment in the cell cycle, characterized by the up-regulation of numerous positive cell cycle regulators. Expression of Pten, the primary negative regulator of PI3K/Akt, was significantly reduced in MEF2D-deficient cardiomyocytes and found to be a direct target gene of MEF2D. Consistent with these findings mutant cardiomyocytes showed activation of the PI3K/Akt survival pathway. Paradoxically, prolonged deficiency of MEF2D in neonatal cardiomyocytes did not trigger proliferation but instead resulted in programmed cell death, which is likely mediated by the E2F transcription factor. These results demonstrate a critical role for MEF2D in cell cycle regulation of post-mitotic, neonatal cardiomyocytes in vitro.
authors: From the Department of Biology, Program in Cell and Molecular Biology, Boston University, Boston, Massachusetts 02215.
authors: Nelsa L
authors: NL
authors: Estrella
authors: From the Department of Biology, Program in Cell and Molecular Biology, Boston University, Boston, Massachusetts 02215.
authors: Amanda L
authors: AL
authors: Clark
authors: From the Department of Biology, Program in Cell and Molecular Biology, Boston University, Boston, Massachusetts 02215.
authors: Cody A
authors: CA
authors: Desjardins
authors: From the Department of Biology, Program in Cell and Molecular Biology, Boston University, Boston, Massachusetts 02215.
authors: Sarah E
authors: SE
authors: Nocco
authors: From the Department of Biology, Program in Cell and Molecular Biology, Boston University, Boston, Massachusetts 02215 fnaya@bu.edu.
authors: Francisco J
authors: FJ
authors: Naya
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle; D049109:Cell Proliferation; D002470:Cell Survival; D050684:E2F Transcription Factors / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D064326:MEF2 Transcription Factors / Q000235:genetics / Q000502:physiology; D009154:Mutation; D032383:Myocytes, Cardiac / Q000166:cytology*; D020411:Oligonucleotide Array Sequence Analysis; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D059467:Transcriptome
chemical_list: D050684:E2F Transcription Factors; D064326:MEF2 Transcription Factors; C578045:MEF2D protein, rat; D034741:RNA, Small Interfering; D019869:Phosphatidylinositol 3-Kinases; D051059:PTEN Phosphohydrolase; C487216:Pten protein, rat; C505410:Casp3 protein, rat; D053148:Caspase 3
keywords: apoptosis; cardiomyocyte; cell cycle; survival; transcription factor; transcriptomics