Shimoda Marine Research Center, University of Tsukuba, Shimoda, Shizuoka, 415-0025, Japan.
Cytoskeleton (Hoboken). 2013 Aug;70(8):453-70. doi: 10.1002/cm.21127. Epub 2013 Aug 19.
An apical tuft, which is observed in a wide range of embryos/larvae of marine invertebrates, is composed of a group of cilia that are longer and less motile than the abundant lateral cilia covering the rest of the embryonic surface. Although the apical tuft has been thought to function as a sensory organ, its molecular composition and roles are poorly understood. Here, we identified a glutathione transferase theta (GSTT) as an abundant and specific component of the apical tuft in sea urchin embryos. The expression of GSTT mRNA increases and becomes limited to the animal plate of the mesenchyme blastula, gastrula, and prism larva. Electron microscopy and tandem mass spectrometry demonstrated that the apical tuft contains almost every axonemal component for ciliary motility. Low concentrations of an inhibitor of glutathione transferase bromosulphophthalein (BSP) induce bending of apical tuft, suggesting that GSTT regulates motility of apical tuft cilia. Embryos treated with BSP swim with normal velocity and trajectories but show less efficiency of changing direction when they collide with an object. These results suggest that GSTT in the apical tuft plays an important role in the mechanical reception for the motility regulation of lateral motile cilia in sea urchin embryos.
顶生纤毛簇广泛存在于多种海洋无脊椎动物的胚胎/幼虫中，由一群比覆盖胚胎其余部分的丰富侧纤毛更长、运动性更弱的纤毛组成。尽管顶生纤毛簇被认为是一种感觉器官，但它的分子组成和功能还知之甚少。在这里，我们鉴定了谷胱甘肽转移酶 theta（GSTT）是海胆胚胎顶生纤毛簇中的丰富且特异性成分。GSTT mRNA 的表达增加，并仅限于中胚层囊胚、原肠胚和棱柱幼虫的动物帽。电子显微镜和串联质谱分析表明，顶生纤毛簇包含几乎所有用于纤毛运动的轴丝成分。低浓度的谷胱甘肽转移酶抑制剂溴磺酞（BSP）诱导顶生纤毛弯曲，表明 GSTT 调节顶生纤毛的运动。用 BSP 处理的胚胎以正常速度和轨迹游动，但在与物体碰撞时改变方向的效率较低。这些结果表明，顶生纤毛簇中的 GSTT 在机械接收方面发挥重要作用，对于海胆胚胎中侧向运动纤毛的运动调节具有重要作用。
