Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, United Kingdom.
Biol Psychiatry. 2011 Jan 15;69(2):173-9. doi: 10.1016/j.biopsych.2010.05.023. Epub 2010 Jul 31.
Many studies in biological psychiatry compare the abundance of individual messenger RNAs between cases and control subjects or, more recently, between genotype groups. Most utilize some form of normalization procedure, usually expressing the transcript(s) of interest relative to that of a housekeeping gene or genes (also called reference genes), to overcome various sources of experimental error. Indeed, normalization is such a standard procedure that its purpose, principles, and limitations are sometimes overlooked, and some papers lack sufficient information as to its implementation. Here, we review the rationales for normalization and argue that in well-conducted psychiatric gene expression studies using human brain tissue, it is reducing intersubject variability rather than experimental error that is the major benefit of normalization. We also review the conceptual and empirical basis for the category of housekeeping genes-i.e., genes with a ubiquitous and invariant expression. We conclude that the evidence is against any such simple categorization and that a more pragmatic, less dogmatic, approach to the selection and implementation of reference genes is required, which takes into account the particular issues that pertain to human brain tissue studies. This pragmatism extends to the issue of whether normalization should be to one or multiple reference genes. We end by making several recommendations toward a more flexible, transparent, and comprehensive approach to data presentation and analysis. We illustrate the review with examples from studies of schizophrenia and mood disorder.
许多生物精神病学研究比较病例和对照个体之间或最近基因型组之间的个别信使 RNA 的丰度。大多数研究采用某种形式的归一化程序，通常将感兴趣的转录本相对于管家基因或基因（也称为参考基因）表达，以克服各种实验误差源。实际上，归一化是如此标准的程序，以至于其目的、原则和限制有时被忽略，并且有些论文缺乏关于其实施的足够信息。在这里，我们回顾了归一化的基本原理，并认为在使用人类脑组织进行的精心设计的精神科基因表达研究中，归一化的主要益处是降低个体间变异性，而不是实验误差。我们还回顾了管家基因（即具有普遍和不变表达的基因）类别在概念和经验方面的基础。我们的结论是，没有任何这样的简单分类的证据，需要采用更务实、不教条的方法来选择和实施参考基因，这需要考虑到与人类脑组织研究相关的特定问题。这种务实主义扩展到了归一化应该针对一个还是多个参考基因的问题。最后，我们提出了一些建议，以实现更灵活、透明和全面的数据表示和分析方法。我们用精神分裂症和情绪障碍研究的例子来说明这一综述。
