Isaji Mamiko, Iwata Hisataka, Harayama Hiroshi, Miyake Masashi
Department of Bioresource and Agrobiosciences, Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan.
Zygote. 2006 May;14(2):157-67. doi: 10.1017/S0967199406003613.
We have shown that the assembly of lamin-associated polypeptide (LAP) 2beta was detected surrounding the chromatin mass around the time of extrusion of the second polar body (PB) in some fertilized oocytes, but not in most activated oocytes, by using A23187 and cycloheximide (CaA + CH). Here, we immunohistologically analysed the correlation between LAP2beta assembly and chromatin condensation in fertilized and activated oocytes during the second meiosis. In bovine cumulus cells, the onset of LAP2beta assembly was observed around anaphase chromosomes with strongly phosphorylated histone H3. No LAP2beta assembled around the chromosomes in the first and second polar bodies and the alternative oocyte chromatin (oCh) if histone H3 was phosphorylated. Only histone H3 of oCh was completely dephosphorylated during the telophase II/G1 transition (Tel II/G1), and then LAP2beta assembled around only the oCh without phosphorylated histone H3. In the oocytes activated by CaA + CH, LAP2beta did not assemble around the condensed oCh during the Tel II/G1 transition, although their histone H3 dephosphorylation occurred rather rapidly compared with that of the fertilized oocytes. The patterns of histone H3 dephosphorylation and LAP2beta assembly in oocytes activated by CaA alone showed greater similarity to those in fertilized oocytes than to those in oocytes activated by CaA + CH. These results show that LAP2beta assembles around only oCh after complete dephosphorylation of histone H3 after fertilization and activation using CaA alone, and that the timing of histone H3 dephosphorylation and LAP2beta assembly in these oocytes is different from that of somatic cells. The results also indicate that CH treatment inhibits LAP2beta assembly around oCh but not histone H3 dephosphorylation.
我们已经表明，在一些受精卵母细胞中，在第二极体（PB）排出时，可检测到核纤层相关多肽（LAP）2β围绕着染色质团块组装，但在大多数经A23187和环己酰亚胺（CaA + CH）激活的卵母细胞中则未检测到。在此，我们通过免疫组织化学分析了第二次减数分裂期间受精卵母细胞和激活卵母细胞中LAP2β组装与染色质凝聚之间的相关性。在牛卵丘细胞中，在后期染色体周围观察到LAP2β组装开始，此时组蛋白H3高度磷酸化。如果组蛋白H3被磷酸化，在第一极体、第二极体和替代卵母细胞染色质（oCh）的染色体周围则没有LAP2β组装。在末期II/ G1期转换（Tel II / G1）期间，只有oCh的组蛋白H3完全去磷酸化，然后LAP2β仅围绕没有磷酸化组蛋白H3的oCh组装。在经CaA + CH激活的卵母细胞中，尽管与受精卵母细胞相比其组蛋白H3去磷酸化发生得相当快，但在Tel II / G1期转换期间，LAP2β并未围绕凝聚的oCh组装。单独用CaA激活的卵母细胞中组蛋白H3去磷酸化和LAP2β组装的模式与受精卵母细胞中的模式相比，与经CaA + CH激活的卵母细胞中的模式更相似。这些结果表明，受精和单独使用CaA激活后，组蛋白H3完全去磷酸化后，LAP2β仅围绕oCh组装，并且这些卵母细胞中组蛋白H3去磷酸化和LAP2β组装的时间与体细胞不同。结果还表明，CH处理会抑制LAP2β围绕oCh的组装，但不会抑制组蛋白H3的去磷酸化。
