Investigation of smooth muscle cell loss in progeria

 描述(申请人提供)：Hutchinson-Gilford早衰症(HGPS)是一种破坏性的早衰疾病。患有HGPS的儿童仅在平均13岁时死于心脏病发作或中风。大多数HGPS病例是由层蛋白A基因C1824T突变引起的。这种突变激活了一个神秘的剪接位点，并产生了一个截短的层蛋白A突变体，名为孕激素。目前尚不清楚孕激素是如何导致HGPS患者发生危及生命的心血管疾病的。先前的研究显示，在人类患者和HGPS小鼠模型中，大动脉中存在大量的平滑肌细胞(SMC)大量丢失的表型，这一表型强烈表明这种表型与HGPS相关的心血管功能障碍和死亡有关。这一建议的主要目标是阐明这种表型背后的分子途径。基于我的团队最近的一项研究(Zhang等人，PNAS 2014)，我们假设了一种机制，即孕激素的存在破坏了聚[ADP-核糖]聚合酶1(PARP1)蛋白的稳定，并导致容易出错的DNA修复途径--非同源末端连接(NHEJ)的激活。因此，错误修复的染色体会在有丝分裂中遇到问题，从而导致HGPS SMC的有丝分裂灾难。在这个建议中，我们建议通过(I)阐明孕激素如何导致PARP1下调，(Ii)研究PARP1中断在HGPS SMC中的后果，以及(Iii)确定NHEJ的衰减是否可以减轻HGPS中SMC的丢失来检验这一想法。我们将使用HGPS患者特异性诱导多能干细胞(IPSCs)在体外建立SMC丢失的模型，并应用HGPS的小鼠模型在体内验证我们的假设。

 DESCRIPTION (provided by applicant): Hutchinson-Gilford progeria syndrome (HGPS) is a devastating premature aging disease. Children with HGPS exclusively die of heart attacks or strokes at an average age of 13 years. The majority of HGPS cases are caused by a mutation C1824T in the lamin A gene. This mutation activates a cryptic splicing site and produces a truncated lamin A mutant named progerin. It is unknown how progerin causes the life-threatening cardiovascular diseases in HGPS patients. Previous research revealed a profound phenotype of massive loss of smooth muscle cells (SMCs) in large arteries in both human patients and HGPS mouse models, strongly suggesting a connection of this phenotype with the cardiovascular malfunction and death associated with HGPS. The primary goal of this proposal is to elucidate the molecular pathway behind this phenotype. Based on a recent study from my group (Zhang et al., PNAS 2014), we hypothesize a mechanism that the presence of progerin destabilizes Poly [ADP-ribose] polymerase 1 (PARP1) protein and leads to the activation of non-homologous end joining (NHEJ), the error-prone DNA repair pathway. Consequently, the mis-repaired chromosomes encounter problems in mitosis, which results in mitotic catastrophe of HGPS SMCs. In this proposal, we propose to test this idea by (i) elucidating how progerin lead to PARP1 down- regulation, (ii) studying the consequence of PARP1 disruption in HGPS SMCs, and (iiI) determining whether attenuation of NHEJ can alleviate SMC loss in HGPS. We will use HGPS patient specific induced pluripotent stem cells (iPSCs) to model SMC loss in vitro as well as apply mouse models of HGPS to test our hypothesis in vivo.