Santini Simona, Bernardi Giorgio
Molecular Evolution Laboratory, Stazione Zoologica "A. Dohrn", Villa Comunale, 80121 Napoli, Italy.
Gene. 2005 Feb 14;346:51-61. doi: 10.1016/j.gene.2004.10.027.
Hox genes encode DNA binding proteins that specify cell fate in the anterior-posterior axis of metazoan animal embryos. While each Hox cluster contains the same genes among the different mammalian species, this does not happen in ray-finned fish, in which both the number and organization of Hox genes and even Hox clusters are variables. Ray-finned fish are believed to have undergone an additional genome duplication that led to the presence of 8 Hox clusters (four twin pairs) in their ancestor. Here we describe the Tilapia (Oreochromis niloticus) Hox genes set in terms of gene content, clusters organization and base composition and compare it with those of pufferfish and zebrafish. We observed that in all these fish, when paralogous genes are conserved in both the twin clusters, the gene which has a lower GC level generally: (i) belongs to the less gene-rich (less conserved) cluster; (ii) has a reduced field of embryonic expression; or (iii) is a pseudogene. The relationship between the decrease of GC level and the loss of conservation and function of one of the paralogous genes from twin clusters is discussed.
Hox基因编码DNA结合蛋白，这些蛋白决定后生动物胚胎前后轴上的细胞命运。虽然在不同的哺乳动物物种中，每个Hox基因簇都包含相同的基因，但在硬骨鱼中情况并非如此，硬骨鱼的Hox基因数量、组织甚至Hox基因簇都是可变的。据信硬骨鱼经历了一次额外的基因组复制，导致其祖先中存在8个Hox基因簇（四对孪生基因簇）。在此，我们从基因含量、基因簇组织和碱基组成方面描述了罗非鱼（尼罗罗非鱼）的Hox基因集，并将其与河豚和斑马鱼的Hox基因集进行了比较。我们观察到，在所有这些鱼类中，当孪生基因簇中的同源基因都保守时，GC水平较低的基因通常：（i）属于基因丰富度较低（保守性较差）的基因簇；（ii）胚胎表达范围缩小；或（iii）是一个假基因。本文讨论了GC水平降低与孪生基因簇中同源基因之一的保守性和功能丧失之间的关系。
