Albalat Ricard
Departament de Genètica, Facultat de Biologia and Institut de Recerca de la Biodiversitat (IrBio), Universitat de Barcelona, Av. Diagonal, 645, E-08028 Barcelona, Spain.
Mol Cell Endocrinol. 2009 Dec 10;313(1-2):23-35. doi: 10.1016/j.mce.2009.08.029. Epub 2009 Sep 6.
Recent discoveries have changed our view of the evolutionary history of retinoic acid (RA) machinery. It is no longer considered a vertebrate or chordate invention but rather a common genetic toolkit of diverse lineages of metazoans. In particular, the basic machinery of RA-metabolizing enzymes, retinoid-binding proteins and RA-binding nuclear receptors has been identified in protostome and deuterostome lineages. Moreover, the retinoid content and the effects of RA treatment have been described in a number of invertebrates, although the physiological role of RA signaling outside vertebrates is still not fully understood. This review summarizes the evidence gathered over many years on the invertebrate RA system, highlighting the ancient origin of the RA genetic machinery and a basic role in neuronal differentiation. Comparison of invertebrate and vertebrate RA toolkits suggests some innovations in the RA machinery of vertebrates that might have contributed to improving the physiological control of retinoid homeostasis, compensating for vitamin A fluctuations in this lineage. Analysis of the RA machinery in invertebrates also reveals independent losses of RA components during evolution, which might be related to changes in embryonic developmental modes and the absence of the temporal collinearity of hox clusters. Additional studies analyzing the biochemical and functional characteristics of the invertebrate RA genetic machinery are warranted to lend experimental support to the hypotheses sketched in this review. These hypotheses open, however, new perspectives toward understanding how the RA genetic machinery evolved to suit the physiological and developmental requirements of metazoans.
最近的发现改变了我们对视黄酸（RA）机制进化史的看法。它不再被认为是脊椎动物或脊索动物的发明，而是后生动物不同谱系共有的基因工具包。特别是，在原口动物和后口动物谱系中已经鉴定出RA代谢酶、类视黄醇结合蛋白和RA结合核受体的基本机制。此外，尽管脊椎动物以外的RA信号传导的生理作用仍未完全了解，但已经在许多无脊椎动物中描述了类视黄醇含量和RA处理的效果。这篇综述总结了多年来收集到的关于无脊椎动物RA系统的证据，强调了RA基因机制的古老起源以及在神经元分化中的基本作用。对无脊椎动物和脊椎动物RA工具包的比较表明，脊椎动物的RA机制有一些创新，可能有助于改善类视黄醇稳态的生理控制，补偿该谱系中维生素A的波动。对无脊椎动物RA机制的分析还揭示了进化过程中RA成分的独立丧失，这可能与胚胎发育模式的变化以及hox簇时间共线性的缺失有关。有必要进行更多研究来分析无脊椎动物RA基因机制的生化和功能特征，为本文概述的假设提供实验支持。然而，这些假设为理解RA基因机制如何进化以适应后生动物的生理和发育需求开辟了新的视角。
