Blachon Stephanie, Cai Xuyu, Roberts Kela A, Yang Kevin, Polyanovsky Andrey, Church Allen, Avidor-Reiss Tomer
Department of Cell Biology, Harvard Medical School, Boston, MA, USA.
Genetics. 2009 May;182(1):133-44. doi: 10.1534/genetics.109.101709. Epub 2009 Mar 16.
Most animals have two centrioles in spermatids (the distal and proximal centrioles), but insect spermatids seem to contain only one centriole (Fuller 1993), which functionally resembles the distal centriole. Using fluorescent centriolar markers, we identified a structure near the fly distal centriole that is reminiscent of a proximal centriole (i.e., proximal centriole-like, or PCL). We show that the PCL exhibits several features of daughter centrioles. First, a single PCL forms near the proximal segment of the older centriole. Second, the centriolar proteins SAS-6, Ana1, and Bld10p/Cep135 are in the PCL. Third, PCL formation depends on SAK/PLK4 and SAS-6. Using a genetic screen for PCL defect, we identified a mutation in the gene encoding the conserved centriolar protein POC1, which is part of the daughter centriole initiation site (Kilburn et al. 2007) in Tetrahymena. We conclude that the PCL resembles an early intermediate structure of a forming centriole, which may explain why no typical centriolar structure is observed under electron microscopy. We propose that, during the evolution of insects, the proximal centriole was simplified by eliminating the later steps in centriole assembly. The PCL may provide a unique model to study early steps of centriole formation.
大多数动物的精子细胞中有两个中心粒（远端中心粒和近端中心粒），但昆虫的精子细胞似乎只含有一个中心粒（富勒，1993年），其功能类似于远端中心粒。我们使用荧光中心粒标记物，在果蝇远端中心粒附近鉴定出一种类似于近端中心粒的结构（即近端中心粒样结构，或PCL）。我们发现PCL具有子代中心粒的几个特征。首先，单个PCL在较老中心粒的近端部分附近形成。其次，中心粒蛋白SAS-6、Ana1和Bld10p/Cep135存在于PCL中。第三，PCL的形成依赖于SAK/PLK4和SAS-6。通过对PCL缺陷进行遗传筛选，我们在编码保守中心粒蛋白POC1的基因中发现了一个突变，该蛋白是四膜虫子代中心粒起始位点的一部分（基尔伯恩等人，2007年）。我们得出结论，PCL类似于正在形成的中心粒的早期中间结构，这可能解释了为什么在电子显微镜下未观察到典型的中心粒结构。我们提出，在昆虫进化过程中，近端中心粒通过消除中心粒组装的后期步骤而被简化。PCL可能为研究中心粒形成的早期步骤提供一个独特的模型。
