Lee Karen W, Webb Sarah E, Miller Andrew L
Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, People's Republic of China.
Zygote. 2006 May;14(2):143-55. doi: 10.1017/S0967199406003637.
We report that the first localized Ca(2+) transient visualized in the blastodisc cortex of post-mitotic zebrafish zygotes has unique features. We confirm that this initial 'furrow positioning' Ca(2+) transient precedes the physical appearance of the first cleavage furrow at the blastodisc surface and that it has unique dynamics, which distinguish it from the subsequent furrow propagation transients that develop from it. This initial transient displays a distinct rising phase that peaks prior to the initiation of the two linear, subsurface, self-propagating Ca(2+) waves that constitute the subsequent furrow propagation transient. Through the carefully timed introduction of the Ca(2+) buffer, dibromo-BAPTA, we also demonstrate the absolute requirement of this initial rising phase Ca(2+) transient in positioning the furrow at the blastodisc surface: no rising phase transient, no cleavage furrow. Likewise, the introduction of the inositol 1,4,5-trisphosphate receptor (IP3R) antagonist, 2-aminoethoxydiphenyl borate, eliminates both the rising phase transient and the appearance of the furrow at the cell surface. On the other hand, antagonists of the ryanodine receptor and NAADP-sensitive channels, or simply bathing the zygote in Ca(2+)-free medium, have no effect on the generation of the rising phase positioning transient or the appearance of the furrow at the surface. This suggests that like the subsequent propagation and deepening/zipping Ca(2+) transients, the rising phase furrow positioning transient is also generated specifically by Ca(2+) released via IP3Rs. We propose, however, that despite being generated by a similar Ca(2+) release mechanism, the unique features of this initial transient suggest that it might be a distinct signal with a specific function associated with positioning the cleavage furrow at the blastodisc surface.
我们报告称，在有丝分裂后的斑马鱼受精卵的胚盘皮层中可视化的首个局部Ca(2+)瞬变具有独特特征。我们证实，这个最初的“沟定位”Ca(2+)瞬变先于胚盘表面第一个卵裂沟的物理出现，并且它具有独特的动态特性，这使其与由它发展而来的后续沟传播瞬变有所区别。这个初始瞬变呈现出一个独特的上升阶段，在构成后续沟传播瞬变的两个线性、亚表面、自传播Ca(2+)波开始之前达到峰值。通过精心定时引入Ca(2+)缓冲剂二溴 - BAPTA，我们还证明了这个初始上升阶段Ca(2+)瞬变对于在胚盘表面定位沟的绝对必要性：没有上升阶段瞬变，就没有卵裂沟。同样，引入肌醇1,4,5 - 三磷酸受体（IP3R）拮抗剂2 - 氨基乙氧基二苯硼酸盐，会消除上升阶段瞬变以及细胞表面沟的出现。另一方面，兰尼碱受体和NAADP敏感通道的拮抗剂，或者仅仅将受精卵置于无Ca(2+)培养基中，对上升阶段定位瞬变的产生或表面沟的出现没有影响。这表明，与后续的传播以及加深/拉链式Ca(2+)瞬变一样，上升阶段沟定位瞬变也是由通过IP3R释放的Ca(2+)特异性产生的。然而，我们提出，尽管这个初始瞬变是由类似的Ca(2+)释放机制产生的，但其独特特征表明它可能是一个具有特定功能的独特信号，与在胚盘表面定位卵裂沟相关。
