Lamin A Mutation and Hutchinson-Gilford Progeria

描述(申请人提供)：Hutchinson-Gilford早衰症(HGPS)是一种以过早衰老为特征的疾病，由LMNA中的一个显性从头突变引起，LMNA编码与核膜相关的中间细丝蛋白LMNA和层蛋白A和C。HGPS中的突变引入了一个异常的剪接位点，导致层蛋白A突变体的表达，其羧基末端缺失了50个氨基酸。突变的层蛋白A被称为孕激素。层蛋白A和C的不同突变会导致心肌病和肌营养不良、部分脂肪营养不良综合征、周围神经病变和非典型沃纳综合征。这些疾病中的一些与HGPS的临床特征相同，而另一些则完全不同。目前尚不清楚Lamins A和C的突变如何导致HGPS或其他疾病。我们假设，这些蛋白质的不同突变会导致核结构和染色质组织的变化，从而导致基因表达的异常。在HGPS中，孕激素的表达，可能与正常的层蛋白A和C的表达降低结合在一起，导致了这一系列事件。我们的目标是检验这一假设。在目标1中，我们将研究孕激素的生物化学及其对细胞核的影响。我们将确定孕激素是否像正常的前层素A一样，是法尼化的，并通过内切蛋白降解来处理。我们将利用荧光漂白方法研究孕激素对细胞核和染色质结构的影响，以及对其他核膜蛋白动态的影响。在目标2中，我们将建立在表皮表达孕激素的转基因小鼠，并确定它们是否出现与人类HGPS和正常衰老皮肤相似的病理和功能异常。我们还将把孕激素转基因小鼠与杂合子Lmna“敲除”小鼠杂交，以确定野生型蛋白水平降低是否有额外的影响。在目标3中，我们将确定法尼基转移酶抑制剂是否阻止孕激素的预烯化，并确定阻断孕激素的预烯化是否能逆转表达孕激素的转基因小鼠的细胞变化和组织异常，从而将目标1和2中的实验工作联系起来。这个项目将建立核蛋白A和C的突变如何导致HGP，以及抑制蛋白质法尼化是否是一种潜在的治疗干预措施。

DESCRIPTION (provided by applicant): Hutchinson-Gilford progeria syndrome (HGPS), a condition with features of premature aging, is caused by a dominant de novo mutation in LMNA, the gene that encodes lamins A and C, intermediate filament proteins associated with the nuclear envelope. The mutation in HGPS introduces an abnormal splice site that leads the expression of a lamin A mutant with 50 amino acids deleted near its carboxyl-terminal end. The mutant lamin A has been called progerin. Different mutations in lamins A and C cause cardiomyopathy and muscular dystrophy, partial lipodystrophy syndromes, a peripheral neuropathy and atypical Werner syndrome. Some of these disorders share clinical features with HGPS while others are quite different. It is not known how mutations in lamins A and C cause HGPS or other diseases. We hypothesize that different mutations in these proteins cause alterations in nuclear structure and chromatin organization that lead to abnormalities in gene expression. In HGPS, progerin expression, possibly in combination with decreased expression of normal lamins A and C, is responsible for this chain of events. Our goal is to test this hypothesis. In Aim 1, we will study the biochemistry of progerin and its effects on the cell nucleus. We will determine if progerin, like normal prelamin A, is farnesylated and processed by endoproteolysis. We will investigate the effects of progerin on nuclear and chromatin structure and on the dynamics of other nuclear envelope proteins using fluorescent photobleaching methods. In Aim 2, we will generate transgenic mice expressing progerin in epidermis and determine if they develop pathological and functional abnormalities similar to those in skin of human subjects HGPS and normal aging skin. We will also cross progerin transgenic mice to heterozygous Lmna "knockout" mice to determine if reduced wild type protein levels have additional effects. In Aim 3, we will determine if a farnesyltransferase inhibitor blocks prenylation of progerin and determine if blocking progerin prenylation reverses cellular alterations and tissue abnormalities in progerin-expressing transgenic mice, hence connecting the experimental work in Aims 1 and 2. This project will establish how mutations in nuclear lamins A and C cause HGPS, and if inhibition of protein farnesylation is a potential therapeutic intervention.