Lamin A Mutation and Hutchinson-Gilford Progeria

描述（由申请人提供）：Hutchinson-Gilford早衰综合征（HGPS）是一种具有早衰特征的疾病，由LMNA的显性新生突变引起，LMNA是编码层蛋白a和C的基因，与核膜相关的中间丝蛋白。HGPS的突变引入了一个异常剪接位点，导致lamin a突变体的表达，其羧基末端附近缺失了50个氨基酸。突变的层粘连蛋白A被称为前蛋白。层粘连蛋白A和C的不同突变导致心肌病和肌肉营养不良、部分脂肪营养不良综合征、周围神经病变和非典型维尔纳综合征。其中一些疾病与HGPS有共同的临床特征，而另一些则截然不同。目前尚不清楚纤层蛋白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导致核结构和染色质组织的改变，从而导致基因表达异常。在HGPS中，progerin的表达，可能与正常层粘连蛋白A和C的表达减少相结合，是导致这一系列事件的原因。我们的目标是验证这个假设。在目的1中，我们将研究progerin的生物化学及其对细胞核的影响。我们将确定是否像正常的前纤层蛋白A一样，被法酰化和内源性蛋白水解处理。我们将利用荧光光漂白方法研究早衰蛋白对核和染色质结构以及其他核包膜蛋白动力学的影响。在Aim 2中，我们将在表皮中产生表达progerin的转基因小鼠，并确定它们是否会出现类似于人类受试者HGPS和正常老化皮肤的病理和功能异常。我们还将把转progerin基因的小鼠与杂合的Lmna敲除小鼠杂交，以确定野生型蛋白水平的降低是否有额外的影响。在Aims 3中，我们将确定法尼基转移酶抑制剂是否阻断早衰蛋白的戊烯酰化，并确定阻断早衰蛋白戊烯酰化是否能逆转表达早衰蛋白的转基因小鼠的细胞改变和组织异常，从而将Aims 1和Aims 2中的实验工作联系起来。该项目将确定核层蛋白A和C的突变是如何引起HGPS的，以及抑制蛋白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.