University of Cyprus, Department of Biological Sciences, P.O. Box 20537, 1678, Nicosia, Cyprus.
University of Cyprus, Department of Biological Sciences, P.O. Box 20537, 1678, Nicosia, Cyprus
G3 (Bethesda). 2019 Nov 5;9(11):3877-3890. doi: 10.1534/g3.119.400715.
Physiology, fitness and disease phenotypes are complex traits exhibiting continuous variation in natural populations. To understand complex trait gene functions transgenic lines of undefined genetic background are often combined to assess quantitative phenotypes ignoring the impact of genetic polymorphisms. Here, we used inbred wild-type strains of the Genetics Reference Panel to assess the phenotypic variation of six physiological and fitness traits, namely, female fecundity, survival and intestinal mitosis upon oral infection, defecation rate and fecal pH upon oral infection, and terminal tracheal cell branching in hypoxia. We found continuous variation in the approximately 150 strains tested for each trait, with extreme values differing by more than four standard deviations for all traits. In addition, we assessed the effects of commonly used transgenic strains and their backcrossed isogenized counterparts, in the same traits plus baseline intestinal mitosis and tracheal branching in normoxia, in heterozygous conditions, when only half of the genetic background was different among strains. We tested 20 non-isogenic strains (10 KK and 10 GD) from the Vienna Resource Center and their isogenized counterparts without Gal4 induction. Survival upon infection and female fecundity exhibited differences in 50% and 40% of the tested isogenic non-isogenic pairs, respectively, whereas all other traits were affected in only 10-25% of the cases. When 11 isogenic and their corresponding non-isogenic lines were expressed ubiquitously with Gal4, 4 isogenic non-isogenic pairs exhibited differences in survival to infection. Furthermore, when a single line was crossed with the same Gal4 transgene inserted in different genetic backgrounds, the quantitative variations observed were unpredictable on the basis of pure line performance. Thus, irrespective of the trait of interest, the genetic background of commonly used transgenic strains needs to be considered carefully during experimentation.
生理学、健康和疾病表型是复杂的特征，在自然群体中表现出连续的变化。为了了解复杂特征的基因功能，通常会将遗传背景未知的转基因系组合起来评估定量表型，而忽略遗传多态性的影响。在这里，我们使用了近交的野生型遗传学参考面板（Genetics Reference Panel）品系来评估六个生理和健康特征的表型变化，即雌性繁殖力、口服感染后的存活率和肠道有丝分裂、口服感染后的排便率和粪便 pH 值、缺氧条件下的终末气管细胞分支。我们发现，在大约 150 个品系中，每个特征的表型都存在连续的变化，所有特征的极值差异超过四个标准差。此外，我们还评估了常用的转基因系及其回交同源系在相同特征中的作用，包括基础肠道有丝分裂和正常条件下的气管分支，在杂合状态下，只有一半的遗传背景在品系之间存在差异。我们测试了来自维也纳资源中心的 20 个非同源系（10 个 KK 和 10 个 GD）及其未诱导 Gal4 的同源系。感染后的存活率和雌性繁殖力在 50%和 40%的测试非同源系对中表现出差异，而其他所有特征仅在 10-25%的情况下受到影响。当 11 个同源系及其对应的非同源系在普遍表达 Gal4 时，有 4 个同源系对在感染后的存活率上表现出差异。此外，当一个单一的系与相同的 Gal4 转基因在不同的遗传背景中杂交时，观察到的定量变化是不可预测的，这不能基于纯系的表现来判断。因此，无论感兴趣的特征如何，在实验过程中都需要仔细考虑常用转基因系的遗传背景。
