Role of SRF in early cardiac Morphogenesis

心脏谱系的确定和心脏特定基因的表达可能需要在心脏前体细胞出现期间发现丰富的转录之间的组合相互作用。血清反应因子(SRF)可能在心脏祖细胞的承诺中起主导作用。最近对小鼠SRF基因座的同源重组敲除支持了SRF是小鼠胚胎发育过程中心脏中胚层出现所必需的这一观察结果。然而，由于SRF缺失突变导致如此早期的胚胎死亡，我们不知道SRF实际上如何促进早期心肌承诺和分化。我们有强有力的证据表明，SRF作为一个肌源性限制性平台与其他调节蛋白相互作用，并最终改变特定基因程序的调节。我们的研究表明，SRF促进了小鼠同源盒转录因子Nkx2-5和GATA4与血清反应元件的结合，导致内源性α-心脏肌动蛋白基因的激活；提供了令人信服的证据，证明SRF、Nkx2-5和GATA-4是内源性α-心脏肌动蛋白基因的相互作用；提供了令人信服的证据，表明SRF、Nkx2-5和GAT-4相互作用并有助于心脏基因的表达。在拟议的研究中，我们将确定SRF基因在心脏基因表达出现期间是如何调节的。在拟议的研究中，我们将确定SRF基因在心脏中胚层的出现和小鼠胚胎心脏的发育和形成过程中是如何调控的。该提案的具体目的是：目的I：编码SRF基因的小鼠基因组基因是如何在心脏发生过程中实现高水平表达的？假设1：生长因子如BMP2/4和FGF4信号激活心脏新月体中SRF基因的表达。重叠转录因子Nkx2-5，Smads，GATA-4和-5，以及Tbx2，3和5由这些生长因子形态原诱导，参与激活和/或抑制SRF的表达，SRF_5是一种替代切片SRF，是阻止心脏发生的主要负性因子。这些转录因子激活心脏特异表达SRF对早期心脏中胚层的确定有直接作用？假设2：在完整的小鼠胚胎中，将中胚层转化为心源性谱系以驱动心脏程序需要SRF基因的活性。SRF在L/R不对称和神经脊细胞向主动脉弓前体细胞的转化中起作用目的III：SRF是否需要与Nkx2-5和GATA4直接结合才能激活生心程序？假设3：MADS Box是一个主调控平台，允许根据特定的因子-因子与其MADS Box AlphaI和/或AlphaII线圈的关联来切换遗传程序。SRF与Nkx2-5和GATA4之间的组合相互作用是中胚层前体细胞向固定的心脏中胚层发展所必需的，需要通过MADS盒的αI线圈进行特定的物理联系。

Specification of the cardiac lineage and expression of cardiac specified genes may require combinatorial interactions between transcription found to enriched during the emergence of cardiac progenitor cells. Serum response factor (SRF) may play a leading role in the commitment of cardiac progenitors The recent homologous recombinant knockout of the murine SRF gene locus supports the observation that SRF is required for the appearance of cardiac mesoderm during mouse embryogenesis. However, because SRF null mutants cause such an early embryonic lethality we do not know how SRF actually contributes to early heart muscle commitment and differentiation. We have strong evidence that SRF acts as a myogenic restricted platform to interact with other regulatory proteins and ultimately alter the regulation of specific gene programs. Our studies suggest that SRF facilities binding of the murine homeobox transcription factor, Nkx2-5 and GATA4 to serum response elements resulting in the activation of the endogenous alpha-cardiac actin gene; provides compelling evidence that SRF, Nkx2-5 and GATA-4 are mutually interactive of the endogenous alpha-cardiac actin gene; provides compelling evidence that SRF, Nkx2-5 and GAT-4 are mutually interactive and instrumental for cardiac gene expression. In the proposed studies, we will determine how the SRF gene is regulated during the appearance of cardiac gene expression. In the proposed studies, we will determine how the SRF gene is regulated during the appearance of cardiac mesoderm and the elaboration and formation of the embryonic mouse heart. The Specific Aims of the proposal are: Aim I: How does the murine genomic loci encoding the SRF gene allow for the high level expression during cardiogenesis? Hypothesis 1: Growth factors such as BMP2/4 and FGF4 signals activate SRF gene expression in the cardiac crescent. Overlapping transcription factors Nkx2-5, Smads, GATA-4 and -5, and TBX2,3 and 5 expressed in the cardiac field, induced by these growth factor morphogens, are involved with activating and or repressing SRF expression, SRF_5 an alternative sliced SRF acts as a dominant negative factor that blocks cardiogenesis. These transcription factors activate cardiac specific expression SRF have a direct role in specifying early cardiac mesoderm? Hypothesis 2: The conversion of mesoderm to cardiogenic lineages to drive the cardiac program in the intact mouse embryo requires SRF gene activity. SRF has a role in L/R asymmetry and the conversion of neural crest cells into aortic arch progenitors Aim III: Does SRF require direct association with Nkx2-5 and GATA4 to activate the cardiogenic program? Hypothesis 3: The MADS Box serves as a master regulatory platform that allows for switching of genetic programs depending upon specific factor-factor associations with either of its MADS Box alphaI and or alphaII coils. Combinatorial interactions shared between SRF with Nkx2-5 and GATA4 is obligatory for the progression of mesoderm precursor cells to committed cardiac mesoderm and requires specific physical association through the alphaI coil of the MADS box.