Study on genetic factors controlling liver copper concentration in sheep

众所周知，绵羊从肝脏排泄过量铜的能力受到损害，因此比其他农场动物更容易受到铜中毒的影响。另一方面，铜缺乏也是养羊业中的一个众所周知的问题。因此，绵羊的日粮中几乎没有足够的铜补充量。有趣的是，不同品种的绵羊对铜缺乏和铜中毒的易感性不同。此外，肝脏铜浓度似乎是高度遗传的，在绵羊品种之间和品种内都是可变的。因此，本研究的目的是找出显著控制绵羊肝脏铜含量的分子遗传因素。在这个项目的第一部分，将测量已经采集的梅里诺兰绵羊品种屠宰羔羊的肝脏样本中的铜浓度。应用SNP芯片，将对其中96个样本的DNA进行基因分型，以确定分布在绵羊基因组中的约60万个遗传变异。由此产生的表型和基因分型数据将用于全基因组关联研究(GWAS)。随后，将筛选与肝脏铜浓度相关的基因组区域，以寻找可以直接控制肝脏铜浓度的遗传变异。对于这一步骤，将采用适当的下一代测序方法。最后，这些遗传变异中最有希望的将在另外收集的五个绵羊品种的表型样本中测试它们对肝脏铜浓度的影响，这些绵羊品种在绵羊生产中具有重要意义，和/或已知它们对铜中毒或铜缺乏的敏感性不同。本项目的研究结果将加深对肝脏铜代谢的遗传调控的认识，并有助于为治疗和预防绵羊铜中毒和铜缺乏提供新的概念。

Sheep are known to be impaired regarding their ability to excrete excess copper (Cu) from the liver and therefore to be more susceptible to Cu intoxication than other farm animals. On the other hand, Cu deficiency is also a known problem in sheep husbandry. In consequence, there is little scope for adequate Cu supplementation in the sheep diet. Interestingly, the susceptibility for Cu deficiency as well as for Cu intoxication varies between sheep breeds. Moreover, liver copper concentration seems to be highly heritable and variable between and within sheep breeds. Hence, it is the aim of this study to identify the molecular genetic factors which significantly control the liver copper concentration in sheep. In the first part of this project, Cu concentration will be measured in already collected liver samples from performance tested slaughter lambs of the Merinoland sheep breed. Applying an SNP chip, DNA from 96 of these samples will be genotyped for about 600,000 genetic variants distributed in the sheep genome. Resulting phenotyping and genotyping data will be used for a genome wide association study (GWAS). Subsequently, genome regions which showed to be associated with liver Cu concentration will be screened for genetic variants which could directly control liver copper concentration. For this step, an appropriate next generation sequencing method will be employed. Finally, the most promising among those genetic variants will be tested for their effect on liver copper concentration in additionally collected and phenotyped samples from five more sheep breeds, which are of importance in sheep production and/or known to differ in their susceptibility to Cu intoxication or deficiency. The results of this project will enhance the knowledge on the genetic control of liver Cu metabolism and can help to develop new concepts for therapy and prevention of Cu intoxication and deficiency in sheep.