Wolf Jason B, Pomp Daniel, Eisen Eugene J, Cheverud James M, Leamy Larry J
Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
Evol Dev. 2006 Sep-Oct;8(5):468-76. doi: 10.1111/j.1525-142X.2006.00120.x.
The contribution that pleiotropic effects of individual loci make to covariation among traits is well understood theoretically and is becoming well documented empirically. However, little is known about the role of epistasis in determining patterns of covariation among traits. To address this problem we combine a quantitative trait locus (QTL) analysis with a two-locus model to assess the contribution of epistasis to the genetic architecture of variation and covariation of organ weights and limb bone lengths in a backcross population of mice created from the M16i and CAST/Ei strains. Significant epistasis was exhibited by 14 pairwise combinations of QTL for organ weights and 10 combinations of QTL for limb bone lengths, which contributed, on average, about 5% of the variation in organ weights and 8% in limb bone lengths beyond that of single-locus QTL effects. Epistatic pleiotropy was much more common in the limb bones (seven of 10 epistatic combinations affecting limb bone lengths were pleiotropic) than the organs (three of the 14 epistatic combinations affecting organ weights were pleiotropic). In both cases, epistatic pleiotropy was less common than single-locus pleiotropy. Epistatic pleiotropy accounted for an average of 6% of covariation among organ weights and 21% of covariation among limb bone lengths, which represented an average of one-fifth (for organ weights) and one-third (for limb bone lengths) of the total genetic covariance between traits. Thus, although epistatic pleiotropy made a smaller contribution than single-locus pleiotropy, it clearly made a significant contribution to the genetic architecture of variation/covariation.
单个基因座的多效性对性状间协变的贡献在理论上已得到很好的理解，并且在实证方面也有了充分的记录。然而，关于上位性在决定性状间协变模式中的作用，我们却知之甚少。为了解决这个问题，我们将数量性状基因座（QTL）分析与双基因座模型相结合，以评估上位性对由M16i和CAST/Ei品系培育出的回交小鼠群体中器官重量和四肢骨长度的变异及协变遗传结构的贡献。器官重量的QTL有14对组合以及四肢骨长度的QTL有10对组合表现出显著的上位性，它们平均分别贡献了器官重量变异的约5%和四肢骨长度变异的8%，超出了单基因座QTL效应的贡献。上位性多效性在四肢骨中比在器官中更为常见（影响四肢骨长度的10个上位性组合中有7个是多效性的，而影响器官重量的14个上位性组合中有3个是多效性的）。在这两种情况下，上位性多效性都比单基因座多效性少见。上位性多效性平均占器官重量间协变的6%和四肢骨长度间协变的21%，分别占性状间总遗传协方差的五分之一（器官重量）和三分之一（四肢骨长度）。因此，尽管上位性多效性的贡献比单基因座多效性小，但它显然对变异/协变的遗传结构做出了显著贡献。
