Johnston Wendy L, Krizus Aldis, Dennis James W
Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Ave, Toronto, ON, M5G 1X5, Canada.
BMC Biol. 2006 Oct 16;4:35. doi: 10.1186/1741-7007-4-35.
Fertilization restores the diploid state and begins the process by which the single-cell oocyte is converted into a polarized, multicellular organism. In the nematode, Caenorhabditis elegans, two of the earliest events following fertilization are secretion of the chitinous eggshell and completion of meiosis, and in this report we demonstrate that the eggshell is essential for multiple developmental events at the one-cell stage.
We show that the GLD (Germline differentiation abnormal)-1-regulated hexosamine pathway enzyme, glucosamine-6-phosphate N-acetyltransferase (GNA)-2, is required for synthesis of uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc), the substrate for eggshell chitin synthesis by chitin synthase-1 (CHS-1). Furthermore, while chs-1(RNAi) or combined RNAi with the chitin-binding proteins, CEJ-1 and B0280.5, does not interfere with normal meiotic timing, lagging chromosomes are observed at meiosis, and polar-body extrusion fails. We also demonstrate that chitin, and either CEJ-1 or B0280.5, are essential for the osmotic/permeability barrier and for movement of the sperm pronucleus/centrosome complex to the cortex, which is associated with the initiation of polarization.
Our results indicate that the eggshell is required in single-cell C. elegans development, playing an essential role in multiple actin-dependent early events. Furthermore, the earliest meiotic roles precede osmotic barrier formation, indicating that the role of the eggshell is not limited to generation of the osmotic barrier.
受精恢复了二倍体状态，并启动了将单细胞卵母细胞转化为极化多细胞生物体的过程。在秀丽隐杆线虫中，受精后最早发生的两个事件是几丁质卵壳的分泌和减数分裂的完成，在本报告中，我们证明卵壳对于单细胞阶段的多个发育事件至关重要。
我们表明，GLD（生殖系分化异常）-1调节的己糖胺途径酶，氨基葡萄糖-6-磷酸N-乙酰转移酶（GNA）-2，是合成尿苷二磷酸-N-乙酰葡糖胺（UDP-GlcNAc）所必需的，UDP-GlcNAc是几丁质合酶-1（CHS-1）合成卵壳几丁质的底物。此外，虽然chs-1（RNA干扰）或与几丁质结合蛋白CEJ-1和B0280.5联合进行RNA干扰不会干扰正常的减数分裂时间，但在减数分裂时观察到滞后染色体，并且极体挤出失败。我们还证明，几丁质以及CEJ-1或B0280.5对于渗透/通透性屏障以及精子原核/中心体复合体向皮层的移动至关重要，这与极化的启动有关。
我们的结果表明，卵壳在单细胞秀丽隐杆线虫发育中是必需的，在多个肌动蛋白依赖性早期事件中起重要作用。此外，最早的减数分裂作用先于渗透屏障形成，这表明卵壳的作用不限于产生渗透屏障。
