Division of Biological Sciences, Computer Science Department, and Informatics Institute, University of Missouri, Columbia, MO 65211, USA.
Proc Natl Acad Sci U S A. 2013 Apr 30;110(18):7383-8. doi: 10.1073/pnas.1305638110. Epub 2013 Apr 15.
Dosage compensation, the equalized X chromosome gene expression between males and females in Drosophila, has also been found in triple X metafemales. Inverse dosage effects, produced by genomic imbalance, are believed to account for this modulated expression, but they have not been studied on a global level. Here, we show a global expression comparison of metafemales (XXX; AA) with normal females (XX; AA) with high-throughput RNA-sequencing. We found that the majority of the X-linked genes in metafemales exhibit dosage compensation with an expression level similar to that of normal diploid females. In parallel, most of the autosomal genes were expressed at about two-thirds the level of normal females, the ratio of inverse dosage effects produced by the extra X chromosome. Both compensation and inverse effects were further confirmed by combination of X-linked and autosomally located miniwhite reporter genes in metafemales and relative quantitative PCR of selected genes. These data provide evidence for an inverse dosage component to X chromosome compensation.
剂量补偿，即雌雄果蝇 X 染色体基因表达的均等化，也在三倍性 XXY 雌性果蝇中被发现。基因组失衡导致的反剂量效应被认为是这种调节表达的原因，但尚未在全局水平上进行研究。在这里，我们使用高通量 RNA 测序，对三倍性 XXY 雌性果蝇（XXX; AA）与正常雌性果蝇（XX; AA）进行了全局表达比较。我们发现，三倍性 XXY 雌性果蝇中大多数 X 连锁基因的表达水平与正常二倍体雌性相似，表现出剂量补偿。同时，大多数常染色体基因的表达水平约为正常雌性的三分之二，这是由额外的 X 染色体产生的反剂量效应的比值。通过在三倍性 XXY 雌性果蝇中组合 X 连锁和常染色体定位的 miniwhite 报告基因，以及对选定基因的相对定量 PCR，进一步证实了补偿和反效应。这些数据为 X 染色体补偿中的反剂量成分提供了证据。
