Department of Research and Development, Hy-Line International, Dallas Center, IA 50063, USA.
Jack Birch Unit for Molecular Carcinogenesis, Department of Biology and The York Biomedical Research Institute, The University of York, York, YO10 5DD, United Kingdom.
Poult Sci. 2021 Jun;100(6):101121. doi: 10.1016/j.psj.2021.101121. Epub 2021 Mar 12.
Avian Leukosis Virus subgroup E (ALVE) integrations are endogenous retroviral elements found in the chicken genome. The presence of ALVE has been reported to have negative impacts on multiple traits, including egg production and body weight. The recent development of rapid, inexpensive and specific ALVE detection methods has facilitated their characterization in elite commercial egg production lines across multiple generations. The presence of 20 ALVE was examined in 8 elite lines, from 3 different breeds. Seventeen of these ALVE (85%) were informative and found to be segregating in at least one of the lines. To test for an association between specific ALVE inserts and traits, a large genotype by phenotype study was undertaken. Genotypes were obtained for 500 to 1500 males per line, and the phenotypes used were sire-daughter averages. Phenotype data were analyzed by line with a linear model that included the effects of generation, ALVE genotype and their interaction. If genotype effect was significant, the number of ALVE copies was fitted as a regression to estimate additive ALVE gene substitution effect. Significant associations between the presence of specific ALVE inserts and 18 commercially relevant performance and egg quality traits, including egg production, egg weight and albumen height, were observed. When an ALVE was segregating in more than one line, these associations did not always have the same impact (negative, positive or none) in each line. It is hypothesized that the presence of ALVE in the chicken genome may influence production traits by 3 mechanisms: viral protein production may modulate the immune system and impact overall production performance (virus effect); insertional mutagenesis caused by viral integration may cause direct gene alterations or affect gene regulation (gene effect); or the integration site may be within or adjacent to a quantitative trait region which impacts a performance trait (linkage disequilibrium, marker effect).
禽白血病病毒 E 亚群 (ALVE) 整合是在鸡基因组中发现的内源性逆转录病毒元件。已经报道了 ALVE 的存在对多个性状具有负面影响，包括产蛋量和体重。最近开发的快速、廉价和特异的 ALVE 检测方法促进了它们在多个世代的优秀商业蛋鸡生产线上的特征描述。在 3 个不同品种的 8 个优秀品系中检查了 20 个 ALVE 的存在。其中 17 个 ALVE（85%）是信息性的，并且至少在一个品系中发现它们在分离。为了检验特定 ALVE 插入与性状之间的关联，进行了一项大型基因型与表型研究。每个品系获得了 500 到 1500 个雄性个体的基因型，并使用了父本-女儿平均值作为表型。通过线性模型对表型数据进行了分析，该模型包括世代、ALVE 基因型及其相互作用的影响。如果基因型效应显著，则拟合 ALVE 拷贝数作为回归，以估计加性 ALVE 基因替代效应。观察到特定 ALVE 插入的存在与 18 个商业相关的生产性能和蛋品质性状之间存在显著关联，包括产蛋量、蛋重和蛋白高度。当 ALVE 在一个以上的品系中分离时，这些关联在每个品系中的影响并不总是相同（负、正或无）。据推测，ALVE 在鸡基因组中的存在可能通过 3 种机制影响生产性状：病毒蛋白的产生可能调节免疫系统并影响整体生产性能（病毒效应）；病毒整合引起的插入突变可能导致直接的基因改变或影响基因调控（基因效应）；或者整合位点可能位于数量性状区域内或附近，从而影响生产性状（连锁不平衡，标记效应）。
