Congenic Mouse Strains Harboring Bone Strength Quantitative Trait Loci

描述（由申请人提供）：预防骨折是一项重要的医疗挑战，因为脆性骨折已经很常见，并且随着美国人口的持续老龄化，这种情况将变得更加普遍。脆性骨折的易感性差异很大，遗传因素占这种差异的50%左右。骨折风险是由青年时期达到的峰值骨量和骨骼形态以及此后骨质流失的速度和程度决定的。小鼠为研究骨骼遗传学提供了有价值的动物模型。几个研究小组已经确定了影响小鼠骨骼强度的基因位点。我们在HcB- 13 × HcB-14和HcB-8 × HcB 23重组基因小鼠的交叉杂交中绘制了生物力学性能定量性状位点（qtl），这些qtl位于染色体1、2、3、4、6、10和x上。我们假设，这些qtl将在分离后对骨骼保持明显的影响，这些qtl具有完全同源的菌株，最终在C3H/DiSnA背景下来自HcB系列共同的C57BL/10ScSnA祖先。我们进一步假设，历史上的重组事件将有助于我们识别qtl背后的基因，就像4号染色体上的情况一样。该项目包括3个具体目标。首先，我们将构建4个含有C57BL/ 10scsna来源的供体片段的同源菌株，针对具有最强大的qtl定位的染色体。其次，我们将对N5F2上的初始基因和N10F2上新建立的基因进行表型分析。因此，在C3H/DiSnA背景下，供体片段基因型对表型的影响将被评估。第三，我们将确定亲本菌株HcB/8、HcB/13、HcB/14、HcB/23的遗传精细结构和早期基因，并努力确定负责基因。从一个定位的QTL到一个已鉴定的基因通常需要几个中间步骤，其中同源菌株特别有价值。首先是确认基因座在被隔离后仍能保持其作用。下一步是利用交叉来细分负责基因的候选区间。HcB菌株已经经历了重组事件，这将证明在这个分析阶段是有用的。这些努力最终在一组有限的候选基因的功能分析。同源菌株在研究单个qtl之间的上位性相互作用方面也有价值。识别影响骨骼生物力学性能的基因并了解它们之间的相互作用将为设计更好的预防骨折的措施提供潜力，无论这些措施是否与衰老、极端负荷条件、其他疾病或药物不良反应有关。公共卫生相关性：我们已经绘制了导致小鼠骨强度和相关特性差异的基因。我们将通过标准的同源育种程序分离包含这些基因的染色体片段。我们会确认在繁殖项目后骨骼效应会持续存在。我们将进行额外的基因实验来确定相关基因。

DESCRIPTION (provided by applicant): Preventing fractures is an important health care challenge, as fragility fractures are already common and will become more so as the US population continues to age. Susceptibility to fragility fractures varies widely with genetic factors accounting for ~50% of this variation. Fracture risk is determined by peak bone mass and skeletal morphology achieved in young adulthood and the rate and extent of bone loss thereafter. Mice provide a valuable animal model for studying skeletal genetics. Several groups have identified genetic loci that contribute to bone strength in the mouse. We have mapped biomechanical performance quantitative trait loci (QTLs) in intercrosses of HcB- 13 x HcB-14 and HcB-8 x HcB 23 recombinant congenic mice, with QTLs located on chromosomes 1, 2, 3, 4, 6, 10, and X. We hypothesize that these QTLs will retain demonstrable effects on the skeleton following isolation as fully congenic strains harboring individual donor segments ultimately derived from HcB series' common C57BL/10ScSnA ancestor on a C3H/DiSnA background. We further hypothesize that historical recombination events will facilitate our efforts to identify the genes underlying the QTLs, as has been the case on chromosome 4. The project includes 3 specific aims. First, we will construct 4 congenic strains harboring C57BL/10ScSnA-derived donor segments, targeting chromosomes with the most robust mapped QTLs. Second, we will phenotype incipient congenics at N5F2 and newly established congenics at N10F2. The donor segment genotype's effect on phenotype in the context of the C3H/DiSnA background will thus be assessed. Third, we will determine the genetic fine structure of the parental strains HcB/8, HcB/13, HcB/14, HcB/23, and the incipient congenics and work toward identifying the responsible genes. Proceeding from a mapped QTL to an identified gene usually requires several intervening steps, for which congenic strains are particularly valuable. The first is to confirm that the locus retains its effect when isolated. The next is to exploit crossovers to subdivide the candidate interval for the responsible gene(s). The HcB strains have undergone recombination events that will prove useful at this stage of analysis. These efforts culminate in functional analyses of a restricted set of candidate genes. The congenic strains will also prove valuable in studying epistatic interactions between the individual QTLs. Identifying genes that affect bone biomechanical performance and understanding their interactions will offer the potential to design better measures to prevent fracture, regardless of whether these are related to aging, extreme loading conditions, other illnesses, or adverse effects from medications. PUBLIC HEALTH RELEVANCE: We have mapped genes that contribute to differences in bone strength and related properties in mice. We will isolate the chromosome segments that contain these genes by a standard congenic breeding program. We will confirm that the bone effects persist following the breeding program. We will perform additional genetic experiments to identify the responsible genes.