Magli Alessandro, Schnettler Erin, Swanson Scott A, Borges Luciene, Hoffman Kirsta, Stewart Ron, Thomson James A, Keirstead Susan A, Perlingeiro Rita C R
Department of Medicine, Lillehei Heart Institute, University of Minnesota, Minneapolis, Minnesota, USA.
Stem Cells. 2014 Aug;32(8):2072-83. doi: 10.1002/stem.1713.
Embryonic stem cells (ESCs) represent an ideal model to study how lineage decisions are established during embryonic development. Using a doxycycline-inducible mouse ESC line, we have previously shown that expression of the transcriptional activator Pax3 in early mesodermal cells leads to the robust generation of paraxial mesoderm progenitors that ultimately differentiate into skeletal muscle precursors. Here, we show that the ability of this transcription factor to induce the skeletal myogenic cell fate occurs at the expenses of the cardiac lineage. Our results show that the PDGFRα+FLK1--subfraction represents the main population affected by Pax3, through downregulation of several transcripts encoding for proteins involved in cardiac development. We demonstrate that although Nkx2-5, Tbx5, and Gata4 negatively affect Pax3 skeletal myogenic activity, the cardiac potential of embryoid body-derived cultures is restored solely by forced expression of Tbx5. Taking advantage of this model, we used an unbiased genome-wide approach to identify genes whose expression is rescued by Tbx5, and which could represent important regulators of cardiac development. These findings elucidate mechanisms regulating the commitment of mesodermal cells in the early embryo and identify the Tbx5 cardiac transcriptome.
胚胎干细胞（ESCs）是研究胚胎发育过程中细胞谱系决定如何建立的理想模型。我们之前利用一种强力霉素诱导的小鼠胚胎干细胞系表明，转录激活因子Pax3在早期中胚层细胞中的表达会导致大量产生轴旁中胚层祖细胞，这些祖细胞最终分化为骨骼肌前体细胞。在此，我们表明这种转录因子诱导骨骼肌生成细胞命运的能力是以牺牲心脏谱系为代价的。我们的结果表明，PDGFRα+FLK1-亚群是受Pax3影响的主要群体，这是通过下调几种编码参与心脏发育的蛋白质的转录本来实现的。我们证明，虽然Nkx2-5、Tbx5和Gata4会对Pax3的骨骼肌生成活性产生负面影响，但仅通过强制表达Tbx5就能恢复胚状体衍生培养物的心脏潜能。利用这个模型，我们采用了一种无偏向的全基因组方法来鉴定其表达可被Tbx5挽救的基因，这些基因可能是心脏发育的重要调节因子。这些发现阐明了调节早期胚胎中胚层细胞定向分化的机制，并确定了Tbx5心脏转录组。
