Genevière Anne-Marie, Aze Antoine, Even Yasmine
CNRS-UMR7628, Observatoire Océanologique de Banyuls, Banyuls-sur-Mer, F-66650 France.
J Soc Biol. 2007;201(1):31-40. doi: 10.1051/jbio:2007004.
Sea urchin is a classical research model system in developmental biology; moreover, the external fertilization and growth of embryos, their rapid division cycle, their transparency and the accessibility of these embryos to molecular visualization methods, made them good specimens to analyze the regulatory mechanisms of cell division. These features as well as the phylogenetic position of sea urchin, close to vertebrates but in an outgroup within the deuterostomes, led scientists working on this model to sequence the genome of the species S. purpuratus. The genome contains a full repertoire of cell cycle control genes. A comparison of this toolkit with those from vertebrates, nematodes, drosophila, as well as tunicates, provides new insight into the evolution of cell cycle control. While some gene subtypes have undergone lineage-specific expansions in vertebrates (i.e. cyclins, mitotic kinases,...), others seem to be lost in vertebrates, for instance the novel cyclin B identified in S. purpuratus. On the other hand, some genes which were previously thought to be vertebrate innovations, are also found in sea urchins (i.e. MCM9). To note is also the absence of cell cycle inhibitors of the INK type, which are apparently confined to vertebrates. The uncovered genomic repertoire of cell-cycle regulators will thus provide molecular tools that should further enhance future research on cell cycle control and developmental regulation in this model.
海胆是发育生物学中的经典研究模型系统；此外，海胆胚胎的体外受精和发育、快速的分裂周期、透明度以及这些胚胎对分子可视化方法的可及性，使其成为分析细胞分裂调控机制的良好样本。这些特征以及海胆在系统发育上的位置，虽接近脊椎动物但属于后口动物中的一个外类群，促使研究该模型的科学家对紫球海胆（S. purpuratus）的基因组进行测序。该基因组包含了完整的细胞周期控制基因库。将这个基因工具包与来自脊椎动物、线虫、果蝇以及被囊动物的基因工具包进行比较，为细胞周期控制的进化提供了新的见解。虽然一些基因亚型在脊椎动物中经历了谱系特异性的扩增（如细胞周期蛋白、有丝分裂激酶等），但其他一些基因亚型在脊椎动物中似乎丢失了，例如在紫球海胆中鉴定出的新型细胞周期蛋白B。另一方面，一些以前被认为是脊椎动物特有的创新基因，在海胆中也能找到（如MCM9）。还需注意的是，INK类型的细胞周期抑制剂不存在，它们显然仅限于脊椎动物。因此，所揭示的细胞周期调节因子的基因组库将提供分子工具，进一步加强对该模型中细胞周期控制和发育调控的未来研究。
