Role of Bop in Cardiac Development and Function

描述(申请人提供)：先天性心脏病和获得性心脏病分别是导致儿童和成人死亡的主要非传染性原因。该项目的长期目标是了解m-Bop蛋白在心肌细胞分化和心脏发育中的作用。BOP编码m-Bop蛋白，m-Bop蛋白在发育早期的小鼠和鸡的心域和肌节以及胚胎和成年小鼠的心肌和骨骼肌中特异表达。M-BOP蛋白包含一个MyND结构域和一个S-ET结构域，前者在其他蛋白质中显示为募集组蛋白脱乙酰基酶(HDAC)，后者在其他蛋白质中显示影响染色质结构，有时是通过内在的组蛋白甲基转移酶(HMT)活性来影响染色质结构。这两种活性都可以通过涉及染色质修饰的表观遗传效应来抑制基因表达。Bop的靶向失活会导致小鼠胚胎第10天(El0)死亡，Bop缺失的胎儿心脏缺乏右室，心肌细胞分化异常。在E7 75 Bop缺失型胚胎的心脏原基中缺乏转录因子Hand2，这表明m-Bop在导致右室发育的早期基因表达级联中发挥了作用。M-Bop在体外由于HDAC的募集而具有抑制活性，并且它在物理上直接或间接地与HDAC相互作用。M-Bop与心脏和骨骼肌特异性转录因子skNAC相互作用，并在体外和体内心肌发生过程中与skNAC共定位。M-BOP还与MITR和HRT2相互作用，MITR是一种肌肉发生的辅助抑制因子，HRT2是一种心脏特异性转录因子。我们计划测试以下假设：1)m-Bop是通过与DNA结合蛋白直接或间接相互作用而在心肌细胞发育和功能早期对染色质修饰的心脏特异调节因子，以及2)m-Bop和skNAC在体外肌肉发生和体内心脏发育过程中以一种有生理意义的方式相互作用。具体目标是1)确定m-Bop的myND、SET和其他结构域促进染色质结构改变和调控转录的机制；2)确定m-Bop/skNAC相互作用的生物学意义和skNAC在心脏发生中的作用。这些研究与先天性心脏病中可能存在的心脏发育不良机制有关。M-Bop似乎通过促进组蛋白修饰，从而以一种谱系特有的方式进行染色质重组，从而特异性地影响心脏发育，使其成为已知的极少数以这种方式工作的蛋白质之一。这为拟议研究中要调查的机制提供了更广泛的相关性。

DESCRIPTION (provided by applicant): Congenital heart disease and acquired heart disease are the leading non-infectious causes of death in children and adults, respectively. The long term objectives of this project are to understand the role of m-Bop proteins in cardiac myocyte differentiation and cardiac development. Bop encodes m-Bop proteins specifically expressed in the heart field and myotome of the mouse and chick early in development as well as in fetal and adult mouse myocardium and skeletal muscle. m-Bop proteins contain both a MYND domain, shown in other proteins to recruit histone deacetylases (HDACs), and a S-ET domain, shown elsewhere to affect chromatin structure, sometimes through intrinsic histone methyltransferase (HMT) activity. Both activities can repress gene expression through epigenetic effects involving chromatin modifications. Targeted inactivation of Bop in mice leads to death at embryonic day 10 (El0 0), and hearts of Bop-null fetuses lack a right ventricle and have abnormal cardiomyocyte differentiation. Absence of the transcription factor, Hand2, from the heart primordia of E7 75 Bop-null embryos suggests a role for m-Bop in an early gene expression cascade that leads to right ventricular development. m-Bop has repressive activity in vitro due to recruitment of HDACs, and it physically interacts directly or indirectly with HDACs. m-Bop interacts with skNAC, a heart- and skeletal muscle-specific transcription factor, and co-localizes with skNAC during myogenesis in vitro and during cardiogenesis in vivo. m-Bop also interacts with MITR, a co-repressor of myogenesis, and HRT2, a heart ventricle-specific transcription factor. We plan to test the hypotheses that 1) m-Bop is a cardiac-specific regulator of chromatin modifications early in cardiomyocyte development and functions through direct and indirect interactions with DNA-binding proteins, and 2) that m-Bop and skNAC interact in a physiologically meaningful manner during myogenesis in vitro and cardiac development in vivo. Specific Aims are 1) To define the mechanisms by which the MYND, SET and other domains of m-Bop promote alterations in chromatin structure and regulate transcription, and 2) To determine the biological significance of m-Bop/skNAC interaction and the role of skNAC during cardiogenesis. These studies are relevant to mechanisms that may underlie ventricular hypoplasia in congenital heart disease. That m-Bop appears to specifically affect heart development by promoting histone modifications and hence chromatin reorganization in a lineage-specific fashion places it among a very few proteins known to operate in this way. This gives a broader relevance to the mechanisms to be investigated in the proposed studies.