Role of Bop in Cardiac Development and Function

描述（由申请人提供）：先天性心脏病和获得性心脏病分别是儿童和成人的主要非感染性死亡原因。本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编码在发育早期小鼠和鸡的心脏区域和肌节中以及在胎儿和成年小鼠心肌和骨骼肌中特异性表达的m-Bop蛋白。 m-Bop蛋白含有MYND结构域和S-ET结构域，MYND结构域在其他蛋白中显示为募集组蛋白脱乙酰酶（HDAC），S-ET结构域在其他地方显示为影响染色质结构，有时通过内在组蛋白甲基转移酶（HMT）活性。 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。小鼠Bop的靶向失活导致胚胎第10天（E10 0）死亡，Bop缺失胎儿的心脏缺乏右心室，并具有异常的心肌细胞分化。 缺乏的转录因子，手2，从心脏原基的E7 - 75 Bop-null胚胎表明的作用，在早期的基因表达级联反应，导致右心室的发展。 由于HDAC的募集，m-Bop在体外具有抑制活性，并且其直接或间接地与HDAC物理相互作用。 m-Bop与skNAC相互作用，skNAC是一种心脏和骨骼肌特异性转录因子，并在体外肌发生过程中和体内心脏发生过程中与skNAC共定位。 m-Bop还与MITR（肌生成的共阻遏物）和HRT 2（心室特异性转录因子）相互作用。 我们计划测试以下假设：1）m-Bop是心肌细胞发育早期染色质修饰的心脏特异性调节剂，并通过与DNA结合蛋白的直接和间接相互作用发挥作用; 2）m-Bop和skNAC在体外肌生成和体内心脏发育期间以生理学上有意义的方式相互作用。 具体目的是：1）确定MYND、SET和m-Bop的其他结构域促进染色质结构改变并调节转录的机制，以及2）确定m-Bop/skNAC相互作用的生物学意义和skNAC在心脏发生过程中的作用。 这些研究与先天性心脏病心室发育不全的机制有关。m-Bop似乎通过促进组蛋白修饰而特异性地影响心脏发育，因此以谱系特异性方式进行染色质重组使其成为已知以这种方式运作的极少数蛋白质之一。这为拟议研究中要研究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.