Novel Mouse Model for Junctional Epidermolysis Bullosa

描述(申请人提供)：大疱性表皮松解症(EB)是一种毁灭性的、可遗传的水疱性皮肤病，其特征是广泛的上皮脆性、水泡和溃疡。准确再现EB样皮肤病的啮齿动物模型是理解EB的潜在遗传学和开发治疗干预措施的迫切需要。我们在LAMC2基因中发现了一种新的、自发的、常染色体隐性的亚型突变，它导致小鼠在其一生中逐渐发展为一种水疱性皮肤病，这种皮肤病与人类泛发性非赫利茨交界性大疱性表皮松解症(JEIB)非常相似。我们的Lamc2jeb纯合子突变小鼠忠实地概括了人类疾病的病理特征，包括进行性真皮/表皮分离、牙釉质发育不良、骨矿化降低、营养不良和过早发病。重要的是，我们的初步数据显示，导入Lamc2jeb突变等位基因的菌株背景可以对JEB的严重程度产生非常强烈的影响。因此，遗传修饰基因座可以决定小鼠是死于毁灭性的疾病还是受到最小的影响。我们建议阐明这种不同易感性的遗传基础。我们的总体假设是，某些修饰基因的等位基因变异对控制JEB的表型严重程度有重大影响。为了验证这一假说，我们的第一个目标是为Jeb的遗传修饰者定义数量性状基因座(QTL)模式。我们将对抗性和敏感小鼠品系之间的杂交进行QTL分析，以确定负责这些效应的QTL(S)。我们的第二个目标是精细定位主效QTL区间以确定候选基因(S)。我们在129X1/SVJ X DBA/1J F2-Lamc2jeb/Lamc2jeb杂交中发现了一个影响皮肤起泡时间的主要19号染色体修饰QTL。我们将使用同源基因减少、亚表型和单倍型分析的组合来精炼负责19号染色体QTL的基因以及可能出现的其他基因。这些研究将使我们有可能将功能属性归因于在我们的小鼠模型中增加或降低JEB风险的QTL，建议候选基因(S)，并表征其作用机制(S)。总体而言，这项工作将为评估相同的基因、编码的蛋白质和相关途径是否对人类Jeb患者构成风险，以及基于修饰基因效应设计治疗方法，甚至作为主要药物靶点打开大门。 公共卫生相关性：我们已经培育了携带自发小鼠突变的小鼠，这是理解交界性大疱性表皮松解症(JEB)在人类中发生的重要临床前工具。在这个独特的模型中表征JEB的遗传基础有望确定新的预后工具、药理靶点，以及一旦了解了机制，就有可能通过改变生活方式来缓和JEB对人类的临床影响。

DESCRIPTION (provided by applicant): Epidermolysis Bullosa (EB) is a devastating, heritable blistering skin disease characterized by widespread epithelial fragility, blistering, and ulceration. Rodent models that faithfully recapitulate EB-like skin diseases are sorely needed to understand the underlying genetics of EB and to develop therapeutic interventions. We identified a novel, spontaneous, autosomal recessive, hypomorphic mutation in the gene Lamc2, which results in mice that progressively develop a blistering skin disease throughout their life that is remarkably similar to human generalized non-Herlitz junctional epidermolysis bullosa (JEB). Our Lamc2jeb homozygous mutant mice faithfully recapitulate the pathological features of the human disease, including progressive dermal/epidermal separation, tooth enamel hypoplasia, lowered bone mineralization, dyspenia, and premature morbidity. Importantly, our preliminary data show that the strain background onto which the Lamc2jeb mutant allele is introgressed can have remarkably strong effects on the severity of JEB. Thus, genetic modifier loci can determine whether mice succumb to devastating disease or are minimally affected. We propose to elucidate the genetic basis of this differential susceptibility. Our overall hypothesis is that allelic variants of certain modifier genes have a major impact in controlling the phenotypic severity of JEB. To test this hypothesis, our first goal is to define quantitative trait locus (QTL) patterns for genetic modifiers of JEB. We will perform QTL analyses of crosses between resistant and susceptible mouse strains to identify the QTL(s) responsible for these effects. Our second goal is to fine map major QTL intervals to identify candidate gene(s). We identified a major Chromosome 19 modifier QTL that affects the time of onset of skin blistering in a 129X1/SvJ X DBA/1J F2-Lamc2jeb/Lamc2jeb cross. We will use a combination of congenic reduction, subphenotypic, and haplotype analyses to hone-in on the genes responsible for the Chromosome 19 QTL and possibly others that emerge. These studies will make it possible to ascribe functional attributes to QTLs that increase or reduce risk for JEB in our mouse model, to suggest the candidate gene(s) responsible, and to characterize their mechanism(s) of action. Overall, the work will open the door for assessment of whether the same genes, encoded proteins, and associated pathways pose risk in human JEB patients and for designing therapeutic approaches based on the modifier gene effects or even as primary pharmaceutical targets. PUBLIC HEALTH RELEVANCE: We have developed mice carrying a spontaneous mouse mutation that is an important preclinical tool for understanding why junctional epidermolysis bullosa (JEB) develops in humans. Characterization of the genetic basis of JEB in this unique model promises to identify novel prognostic tools, pharmacological targets, and, once the mechanism is understood, potential ways to modify lifestyle to moderate the clinical effects of JEB in humans.