Tian Ai-Guo, Deng Wu-Min
Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370, USA.
Dev Biol. 2009 Mar 15;327(2):458-64. doi: 10.1016/j.ydbio.2008.12.031. Epub 2009 Jan 3.
The formation of an anterior-posterior (AP) gradient of microtubules in Drosophila oocytes is essential for specification of the AP axis. Proper microtubule organization in the oocyte requires the function of serine/threonine kinase Par-1. The N1S isoform of Par-1 is enriched at the posterior cortex of the oocyte from stage 7 of oogenesis. Here we report that posterior restriction of Par-1 (N1S) kinase activity is critical for microtubule AP gradient formation. Egg chambers with excessive and ectopic Par-1 (N1S) kinase activity in the germline cells display phenotypes similar to those of egg chambers treated with the microtubule-depolymerizing drug colcemid: depolymerization of microtubules in the oocyte and disruption of oocyte nucleus localization. A phosphorylation target of Par-1, the microtubule-associated protein Tau, is also involved in oocyte polarity formation, and overexpression of Tau alleviates the phenotypes caused by ectopic Par-1 (N1S) kinase activity, suggesting that Par-1 regulates oocyte polarity at least partly through Tau. Our findings reveal that maintaining proper levels of Par-1 at correct position in the oocyte is key to oocyte polarity formation and that the conserved role of Par-1 and Tau is crucial for the establishment of an AP gradient of microtubules and for AP axis specification.
果蝇卵母细胞中微管前后（AP）梯度的形成对于AP轴的特化至关重要。卵母细胞中微管的正确组织需要丝氨酸/苏氨酸激酶Par-1的功能。从卵子发生的第7阶段开始，Par-1的N1S亚型在卵母细胞的后皮质富集。我们在此报告，Par-1（N1S）激酶活性的后向限制对于微管AP梯度的形成至关重要。生殖系细胞中具有过量和异位Par-1（N1S）激酶活性的卵室表现出与用微管解聚药物秋水仙酰胺处理的卵室相似的表型：卵母细胞中微管的解聚和卵母细胞核定位的破坏。Par-1的磷酸化靶点、微管相关蛋白Tau也参与卵母细胞极性的形成，并且Tau的过表达减轻了由异位Par-1（N1S）激酶活性引起的表型，这表明Par-1至少部分地通过Tau调节卵母细胞极性。我们的研究结果表明，在卵母细胞的正确位置维持适当水平的Par-1是卵母细胞极性形成的关键，并且Par-1和Tau的保守作用对于微管AP梯度的建立和AP轴的特化至关重要。
