Genetics of Sagg: A Heritable Mouse Model for Cutis Laxa

描述（由申请方提供）：拉克萨是一种原因不明的皮肤结缔组织疾病，其特征为皮肤下垂、过早起皱和皮肤弹性降低。它以遗传和获得的形式发生。虽然经典的疾病只影响皮肤，但它似乎发生在许多变化或子集中，影响一些患者的各种其他器官。建立一种动物模型来研究皮肤松弛拉克萨的分子机制将是非常有用的。最近，描述了携带Sagg突变的小鼠的存在（1）。这些小鼠被命名为Sagg，因为它们具有遗传性下垂或松弛的皮肤，类似于拉克萨患者的皮肤特征。与松弛的皮肤相关的是真皮中胶原蛋白和弹性蛋白的大量减少。我们提出这种松散的皮肤突变小鼠品系，命名为Sagg，作为一个模型的遗传形式的皮肤拉克萨。在此R21申请中，我们打算细化Sagg突变的位置，并表征该突变小鼠的表型，以确定其是否是皮肤拉克萨的合适模型。在Specific Alm I中，我们将从（1231-1/140 Sagg/+ x CAST/ei）F1 x CAST/ci的亚种间回交获得Sagg N2小鼠，并构建分子标记DIMU 232和DIAM 234之间重组事件的精细图谱。我们将划定的区域，其中Sagg居住在小于2厘米，作为一个初步的，但必要的步骤，染色体步行实验，旨在定位和克隆基因。在具体目标2中，我们将通过对皮肤、肺、肾、心脏和主动脉进行组织学和生物化学分析，以每月一次的间隔从1至12个月龄表征Saggl+小鼠的表型。这些研究将包括原位杂交，以确定I型和III型胶原蛋白和弹性蛋白mRNA在这些组织中的空间和时间表达。将使用真皮成纤维细胞进行北方印迹分析，以检查其他基因的稳态mRNA水平，这些基因包括：A;根据特异性目的1的结果鉴定的候选基因，和B;编码预期可能受Sagg突变影响的细胞外基质组分（EMC）的基因。这些实验还将包括编码参与降解和去除EMC的酶的基因。进行这些研究是为了阐明Sagg突变引起的下游分子事件。

DESCRIPTION (provided by applicant): Cutis laxa is a connective tissue disease of the skin of unknown cause, characterized by sagging skin, premature wrinkling and reduced skin elasticity. It occurs in heritable and acquired forms. Although classically the disease only affects the skin it appears to occur in many variations or subsets affecting a variety of other organs in some patients. An animal model to study the molecular mechanisms of cutis laxa would be extremely useful. Recently, the existence of mice carrying the Sagg mutation was described (1). These mice were named Sagg because they have heritable saggy or loose skin that resembles characteristics of skin found in patients with cutis laxa. Associated with the loose skin is a profound reduction of collagen and elastin in the dermis. We propose this loose skin mutant mouse strain, named Sagg, as a model for the heritable form of cutis laxa. In this R21 application, we intend to refine the position of the Sagg mutation and to characterize the phenotype of this mutant mouse to determine whether it is a suitable model for cutis laxa. In Specific Alm I we will obtain Sagg N2 mice from an intersubspecific backcross of (1231-1/140Sagg/+ x CAST/ei)Fl x CAST/ci and construct a fine-map of the recombination events between the molecular markers, DIMU232 and DIAM234. We will delimit the region in which Sagg resides to less than 2 cM, as a preliminary but necessary step for chromosome walking experiments aimed at locating and cloning the gene. In Specific Aim 2, we will characterize the phenotype of Saggl+ mice at monthly intervals from ages I to 12 months by performing histological and biochemical analyses on the skin, lungs, kidney, heart and aorta. These studies will include in situ hybridizations to determine the spatial and temporal expression of collagen types I and III and elastin mRNAs in these tissues. Dermal fibroblasts will be used for Northern blot analyses to examine the steady state mRNA levels of additional genes which will include: A; candidate genes which have been identified from the results of Specific Aim 1, and B; genes encoding extracellular matrix components (EMC) which might be expected to be affected by the Sagg mutation. These experiments will also include genes encoding enzymes involved in the degradation and removal of the EMC. These studies will be undertaken in order to elucidate the downstream molecular events resulting from the Sagg mutation.