GENETIC ANALYSIS OF BONE FRAGILITY IN RATS

这项研究的目标是确定影响骨骼脆性的特定遗传变异。在这个项目的前一阶段，我们发现了一个近交系大鼠(F344)，它比第二个品系(LEW)具有更低的骨密度和更多的脆弱骨骼。从F344和卢大鼠品系中，我们创建了一个用于遗传图谱的F2群体。我们在第1、2、4、5、7、8、10、15和19号染色体上定位了骨骼表型的数量性状基因座(QTL)。这些QTL的LOD得分在4.0~19.6之间，极显著(p&lt；0.05)。其中两个基因座的QTL，CHRAS 5和8，与在我们的同胞对群体中观察到的QTL是同线的(项目1和2)。大鼠Chr5上的QTL与人Chr1p是同线的，这被证明与股骨近端骨密度连锁。此外，大鼠Chr 8上的QTL与人Chr 15q是同线的，这被证明与髋骨密度有关。在未来五年内，我们将通过培育同源大鼠来分离关键QTL的效应。每个QTL可能与一个或多个其他QTL相互作用，从而使遗传图景复杂化。分离单个QTL效应的一种方法是创建一个同源系。这将通过回交育种策略来完成。将F344大鼠与LEW大鼠杂交，其后代与LEW大鼠回交10代。 通过每一代，大鼠将在QTL上进行基因分型，以识别QTL内的F344 DMA携带者。得到的同源系长度超过99.9%，在QTL上只有一小部分F344的DNA片段。我们计划为chRAS5和8 QTL建立同源大鼠品系，以分离与人类QTL匹配的大鼠染色体区域。除了同源基因的方法，我们还将研究基因在骨骼中的表达，以确定候选基因。基因表达将使用Affymetrix大鼠微阵列进行测量。我们将比较F344和同源系与卢大鼠的骨骼基因表达，以评估骨骼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，并且也是差异表达的基因。这些基因将被标记为强有力的候选基因，并在我们的兄弟姐妹对中进行测试 人口(经济学人项目)。我们假设使用这种方法将识别出许多候选基因。

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.