Mus musculus Transcriptome or Gene expression

Systemic sclerosis (SSc) is a polygenic, autoimmune disorder of unknown etiology, characterized by the excessive accumulation of extracellular matrix (ECM) proteins, vascular alterations, and autoantibodies. The tight skin (Tsk)2/+ mouse model of SSc demonstrates signs similar to SSc including tight skin and excessive deposition of dermal ECM proteins. By linkage analysis, we mapped the Tsk2 gene mutation to less than 3 megabases on chromosome 1. We performed both RNA sequencing of skin transcripts and genome capture DNA sequencing of the region spanning this interval in Tsk2/+ and wild-type littermates. A missense point mutation in the procollagen III amino terminal propeptide segment (PIIINP) of Col3a1 was found to be the best candidate for Tsk2, so both in vivo and in vitro genetic complementation tests were used to prove that this Col3a1 mutation is the Tsk2 gene. All previously documented mutations in the human Col3a1 gene are associated with Ehlers-Danlos syndrome, a connective tissue disorder that leads to a defect in type III collagen synthesis. The Tsk2 point mutation is the first documented gain-of-function mutation associated with Col3a1, which leads instead to fibrosis. This discovery provides insight into the mechanism of skin fibrosis manifested by Tsk2/+ mice.

系统性硬化症（Systemic sclerosis, SSc）是一种病因未明的多基因自身免疫性疾病，其特征为细胞外基质（extracellular matrix, ECM）蛋白过度蓄积、血管病变以及自身抗体产生。用于研究SSc的紧皮症(Tsk)2/+小鼠模型可表现出与SSc相似的症状，包括皮肤紧绷及真皮层细胞外基质蛋白过度沉积。通过连锁分析，我们将Tsk2基因突变定位至1号染色体上小于3兆碱基的区间内。我们对Tsk2/+小鼠及其野生型同窝仔鼠的皮肤转录本进行了RNA测序，并对该定位区间区域开展了基因组捕获DNA测序。研究发现，Col3a1基因中编码III型前胶原氨基端前肽结构域（procollagen III amino terminal propeptide segment, PIIINP）的区域存在一处错义点突变，该突变是Tsk2的最佳候选致病突变；随后通过体内及体外遗传互补试验证实，该Col3a1突变即为Tsk2基因的致病变异。此前文献报道的人类COL3A1基因所有突变均与埃勒斯-当洛综合征（Ehlers-Danlos syndrome）相关，该疾病是一种结缔组织病，会导致III型胶原合成缺陷。本次发现的Tsk2点突变是首个被报道的与COL3A1相关的功能获得性突变，该突变可引发纤维化进程。这一发现为阐明Tsk2/+小鼠所表现的皮肤纤维化机制提供了新的见解。