Disproportionate Dwarfism in the Mouse Mutant Rhizomelia

描述(申请人提供)：脊椎动物骨骼是一种重要的解剖系统，为活动的身体提供结构支持，保护重要的内脏器官，并为造血系统提供友好的环境。这些骨骼结构发展的一系列过程称为骨骼形态发生。骨骼形态发生的缺陷表现为骨软骨发育不良，这是一大组状态障碍，在人类人口中每5000人中就有1人受到影响，近1%的围产儿死亡。这些疾病的严重程度从相对轻微到严重不等。较轻微的情况可能会影响诸如身高、行动能力、活动量和性行为等生活质量问题。中度情况可能包括神经和骨科并发症。最严重的病例可能导致围产期死亡。 这项建议的目的是研究在携带根瘤(RZM)突变的小鼠中发现的不成比例侏儒症的分子遗传学基础，RZM是一种新型的转基因诱导突变，可导致轴向和附件骨骼的骨骼生长异常，包括肱骨和股骨缩短、胸腔狭窄、尾巴缩短和头面部缺陷。这项建议的具体目的是为了了解RZM表型的分子遗传学基础。首先，将进行实验以确定RZM表型是功能获得(GoF)机制还是功能丧失(LoF)机制造成的。使用基于胚胎干细胞的方法，将构建跨越RZM基因座的缺失(Delta)。在创造了携带缺失的小鼠后，将使用遗传杂交将RZM置于反式到包含性缺失(RZM/A)中。对由此产生的表型的评估应该允许人们区分Gof和LoF假说。其次，将进行分子研究，以克隆转基因插入两侧的基因组区域，并评估与骨骼形态发生有关的连锁候选基因和其他关键角色的表达。这项研究和后续研究的最终目标是使用这种独特的动物和转基因本身提供的分子标签作为进入协调骨骼发育的结构和调控基因网络的一种手段。

DESCRIPTION (provided by applicant): The vertebrate skeleton is an important anatomical system providing structural support for a motile body, protection for vital internal organs, and a hospitable environment for the hematopoetic system. The set of processes by which these bony structures develop is known as skeletal morphogenesis. Defects in skeletal morphogenesis are manifested as osteochondrodysplasias, a large group of statural disorders affecting more than 1 person in 5000 in the human population and observed in nearly one percent of perinatal deaths. These conditions range in seriousness from relatively mild to severe. The more mild conditions may affect such quality of life issues as stature, mobility, activity and sexuality. Moderate conditions may include neurological and orthopedic complications. The most severe cases can result in perinatal lethality. The purpose of this proposal is to study the molecular genetic basis of disproportionate dwarfism seen in mice carrying the rhizomelia (rzm) mutation, rzm is a novel, transgene-induced mutation that causes skeletal growth aberrations in both the axial and appendicular skeleton including shortened humeri and femora, narrowed thoracic cavity, shortened tail, and craniofacial defects. The specific aims of this proposal are focused at understanding the molecular genetic basis of the rzm phenotype. First, experiments will be performed to determine whether the rzm phenotype results from a gain-of-function (GoF) or loss-of-function (LoF) mechanism. Using an embryonic stem (ES) cell-based approach, a deletion (delta) will be constructed which spans the rzm locus. After creating deletion-bearing mice, genetic crosses will be used to place rzm in trans to the encompassing deletion (rzm/A). Assessment of the resulting phenotype should allow one to discriminate between the GoF and LoF hypotheses. Second, molecular studies will be performed to clone the genomic region flanking the transgene insertion and to assess the expression of linked candidate genes and other critical players implicated in skeletal morphogenesis. The ultimate goal of this and subsequent studies is to use this unique animal and the molecular tag provided by the transgene itself as a means of entry into the network of structural and regulatory genes that coordinate skeletal development.