Genetics of Sagg: A Heritable Mouse Model for Cutis Laxa

描述(申请人提供)：皮肤松弛是一种原因不明的皮肤结缔组织病，以皮肤松弛、过早皱纹和皮肤弹性降低为特征。它以可遗传和后天获得的形式出现。虽然传统上这种疾病只影响皮肤，但它似乎发生在许多变异或亚型中，影响到一些患者的其他各种器官。研究皮肤松弛的分子机制的动物模型将是非常有用的。最近，携带SAGG突变的小鼠的存在被描述(1)。这些小鼠之所以被命名为Sagg，是因为它们具有遗传的松弛或松弛的皮肤，这类似于皮肤松弛患者的皮肤特征。与松弛的皮肤相关的是真皮中胶原和弹性蛋白的显著减少。我们建议将这种松弛的皮肤突变小鼠品系命名为SAGG，作为可遗传形式的皮肤松弛的模型。在R21的应用中，我们打算改进SAGG突变的位置，并对该突变小鼠的表型进行表征，以确定它是否适合皮肤松弛模型。在特定的Alm I中，我们将从(1231-1/140 Sagg/+x Cast/Ei)Fl x Cast/Ci的亚种间回交获得Sagg N2小鼠，并构建分子标记DIMU232和DIAM234之间的重组事件的精细图谱。我们将把SAGG所在的区域限制在2厘米以下，作为定位和克隆该基因的染色体行走实验的初步但必要的步骤。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化分析，从I到12个月的每月间隔来表征Saggl+小鼠的表型。这些研究将包括原位杂交，以确定I型和III型胶原和弹性蛋白mRNAs在这些组织中的时空表达。真皮成纤维细胞将被用于Northern杂交分析，以检测其他基因的稳态mRNA水平，这些基因将包括：A；从特定目标1和B的结果中识别的候选基因；编码可能受SAGG突变影响的细胞外基质成分(EMC)的基因。这些实验还将包括编码参与EMC降解和去除的酶的基因。这些研究将被用来阐明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.