Genetics of Sagg: A Heritable Mouse Model for Cutis Laxa

描述（由申请人提供）：皮肤松弛症是一种原因不明的皮肤结缔组织疾病，以皮肤松弛、过早起皱、皮肤弹性降低为特征。它以遗传和获得的形式出现。虽然这种疾病通常只影响皮肤，但在一些患者中，它似乎出现了许多变异或亚群，影响了各种其他器官。建立动物模型来研究皮肤松弛的分子机制是非常有用的。最近，有报道称存在携带Sagg突变的小鼠(1)。这些老鼠被命名为Sagg，因为它们具有遗传性的松弛或松弛的皮肤，类似于皮肤松弛症患者的皮肤特征。与皮肤松弛相关的是真皮中胶原蛋白和弹性蛋白的大量减少。我们提出这种松弛的皮肤突变小鼠菌株，命名为Sagg，作为皮肤松弛症遗传形式的模型。在这项R21应用中，我们打算完善Sagg突变的位置，并表征该突变小鼠的表型，以确定它是否是皮肤松弛症的合适模型。在Specific Alm I中，我们将从（1231-1/140Sagg/+ x CAST/ei）Fl x CAST/ci的亚种间回交中获得Sagg N2小鼠，并构建分子标记DIMU232和DIAM234之间重组事件的精细图谱。我们将把Sagg所在的区域划定为小于2厘米，作为染色体行走实验的初步但必要的步骤，旨在定位和克隆该基因。在特异性目标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，每个月对1至12个月的Saggl+小鼠进行表型表征。这些研究将包括原位杂交，以确定这些组织中I型和III型胶原蛋白和弹性蛋白mrna的空间和时间表达。真皮成纤维细胞将用于Northern blot分析，以检查其他基因的稳态mRNA水平，这些基因包括：A；从Specific Aim 1和B的结果中鉴定出的候选基因；编码细胞外基质成分（EMC）的基因可能会受到Sagg突变的影响。这些实验还将包括编码参与降解和去除EMC的酶的基因。这些研究将进行，以阐明由Sagg突变导致的下游分子事件。

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.