GENETIC ANALYSIS OF BONE FRAGILITY IN RATS

这项研究的目的是确定影响骨脆性的特定遗传变异。在本项目的前期研究中，我们鉴定了一种近交系大鼠（F344），其骨矿物质密度低于第二种大鼠（LEW），骨骼更脆弱。从F344和LEW大鼠品系，我们创建了用于遗传作图的F2群体。我们在第1、2、4、5、7、8、10、15和19号染色体上鉴定了骨骼表型的数量性状位点。这些QTL的LOD得分范围为4.0至19.6，并且在p<0.05时是显著的。在这些位点中的两个，Chrs 5和8，QTL与我们的同胞对群体中观察到的QTL同线（项目1和2）。大鼠Chr 5上的QTL与人类Chr 1p同线，这被证明与股骨近端骨密度相关。此外，大鼠Chr 8上的QTL与人类Chr 15 q同线，这被证明与髋部BMD相关。在未来五年内，我们将通过培育同类大鼠来分离关键QTL的效应。每个QTL可能与一个或多个其他QTL相互作用，从而使遗传图谱复杂化。分离单个QTL效应的一种方法是创建同源系。这将使用回交育种策略来完成。F344大鼠将与LEW大鼠杂交，后代与LEW大鼠回交10代。 在每一代中，将在QTL处对大鼠进行基因分型，以鉴定QTL内F344 DMA的携带者。所得到的同源系的LEW超过99.9%，在QTL处仅具有小区域的F344 DMA。我们计划为Chrs 5和8 QTL建立同源大鼠品系，以分离大鼠中与人类QTL匹配的染色体区域。除了同源的方法，我们将检查骨中的基因表达，以确定候选基因。将使用Affyellow大鼠微阵列测量基因表达。我们将比较F344和同源系与LEW大鼠的骨骼基因表达，以评估骨生长过程中的差异基因表达。我们的目标是确定属于QTL的基因，也是差异表达。这些基因将被标记为强有力的候选者，并在我们的兄弟姐妹中进行测试。 经济人项目（Project by Econs）我们假设，许多候选基因将被确定使用这种方法。

The goal of this research is to identify specific genetic variants that affect bone fragility. In the previous iinding period of this project, we identified an inbred strain of rats (F344) that has lower bone mineral density and more fragile bones than a second rat strain (LEW). From F344 and LEW rat strains, we created an F2 population for genetic mapping. We identified quantitative trait loci (QTLs) for skeletal phenotypes on Chromosomes (Chrs) 1, 2, 4, 5, 7, 8, 10,15 and 19. LOD scores for these QTLs ranged from 4.0 to 19.6 and were significant at p<0.05. QTLs at two of these loci, Chrs 5 and 8, are syntenic with QTLs observed in our sibling pair population (Projects 1 and 2). The QTL on rat Chr 5 is syntenic with human Chr 1p, which was shown to be linked to proximal femoral bone density. In addition, the QTL on rat Chr 8 is syntenic with human Chr 15q that was shown to be linked to hip BMD. In the next five years, we will isolate the effects of key QTLs by breeding congenic rats. Each QTL may nteract with one or more other QTLs thus complicating the genetic picture. One way to isolate the effect of a single QTL is to create a congenic line. This will be done using a backcross breeding strategy. The F344 rats will be intercrossed with LEW rats and the offspring backcrossed with LEW rats for 10 generations. Through each generation, the rats will be genotyped at the QTL to identify carriers of F344 DMA within the QTL. The resulting congenic line is over 99.9% LEW with only a small region of F344 DMA at the QTL. We plan to make congenic rat lines for the Chrs 5 and 8 QTLs to isolate the chromosomal regions in the rat that match QTLs in humans. In addition to the congenic approach, we will examine gene expression in bone to identify candidate genes. Gene expression will be measured using the Affymetrix rat microarray. We will compare skeletal gene expression in F344 and congenic lines with LEW rats to assess differential gene expression during bone growth. Our goal is to identify genes that fall within the QTLs and are also differentially expressed. These genes will be flagged as strong candidates and tested in our sibling pair population (Project by Econs). We hypothesize that numerous candidate genes will be identified using this method.