Nogi Taisaku, Levin Michael
Department of Cytokine Biology, The Forsyth Institute, 140 The Fenway, Boston, MA 02115, USA.
Dev Biol. 2005 Nov 15;287(2):314-35. doi: 10.1016/j.ydbio.2005.09.002. Epub 2005 Oct 21.
Planaria possess remarkable powers of regeneration. After bisection, one blastema regenerates a head, while the other forms a tail. The ability of previously-adjacent cells to adopt radically different fates could be due to long-range signaling allowing determination of position relative to, and the identity of, remaining tissue. However, this process is not understood at the molecular level. Following the hypothesis that gap-junctional communication (GJC) may underlie this signaling, we cloned and characterized the expression of the Innexin gene family during planarian regeneration. Planarian innexins fall into 3 groups according to both sequence and expression. The concordance between expression-based and phylogenetic grouping suggests diversification of 3 ancestral innexin genes into the large family of planarian innexins. Innexin expression was detected throughout the animal, as well as specifically in regeneration blastemas, consistent with a role in long-range signaling relevant to specification of blastema positional identity. Exposure to a GJC-blocking reagent which does not distinguish among gap junctions composed of different Innexin proteins (is not subject to compensation or redundancy) often resulted in bipolar (2-headed) animals. Taken together, the expression data and the respecification of the posterior blastema to an anteriorized fate by GJC loss-of-function suggest that innexin-based GJC mediates instructive signaling during regeneration.
涡虫具有非凡的再生能力。将其切断后，一个芽基会再生出头部，而另一个则形成尾部。先前相邻的细胞能够呈现出截然不同的命运，这可能是由于远距离信号传导，使得细胞能够确定相对于剩余组织的位置以及剩余组织的身份。然而，这一过程在分子层面上尚不清楚。基于缝隙连接通讯（GJC）可能是这种信号传导基础的假设，我们克隆并表征了涡虫再生过程中Innexin基因家族的表达情况。根据序列和表达情况，涡虫的Innexin可分为3组。基于表达的分组与系统发育分组之间的一致性表明，3个祖先Innexin基因分化成了庞大的涡虫Innexin基因家族。在整个动物体内都检测到了Innexin的表达，在再生芽基中也有特异性表达，这与Innexin在与芽基位置身份确定相关的远距离信号传导中所起的作用一致。暴露于一种不区分由不同Innexin蛋白组成的缝隙连接（不存在补偿或冗余）的GJC阻断试剂中，常常会导致出现双极（双头）动物。综上所述，表达数据以及通过GJC功能丧失将后芽基重新指定为前端命运的结果表明，基于Innexin的GJC在再生过程中介导了指导性信号传导。
