Protein phosphatase 2A is essential to maintain meiotic arrest, and to prevent Ca2+ burst at spawning and eventual parthenogenesis in the larvacean Oikopleura dioica.
Protein phosphatase 2A is essential to maintain meiotic arrest, and to prevent Ca2+ burst at spawning and eventual parthenogenesis in the larvacean Oikopleura dioica.
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蛋白磷酸酶 2A 对于维持幼体 Oikopleura dioica 减数分裂停滞、防止产卵时 Ca2 爆发以及最终的孤雌生殖至关重要。
DOI：
10.1016/j.ydbio.2019.12.005
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Omotezako T and Nishida N
中科院分区：
文献类型：
--
作者：
Matsuo M;Onuma TA;Omotezako T and Nishida N
大多数动物的未受精卵在减数分裂细胞周期的某个点被阻止。减数分裂的重新开始和胚胎发生的开始是由受精触发的。这种停滞对于防止孤雌激活和促进受精发育的正确启动是必不可少的。在研究脊索动物发育的简单模式生物-异侧长角大孔虫中，未受精卵被阻滞在减数分裂Ⅰ中期。我们在这里表明，蛋白磷酸酶2A（PP 2A）是必不可少的卵母细胞产卵后维持减数分裂停滞。在母体因子的功能筛选中发现，母体PP 2A催化亚基的敲低（KD）导致未受精卵在产卵后自发释放极体，然后在未受精的情况下开始假卵裂，即孤雌生殖。孤雌生殖的胚胎由于缺少中心体而不能进行正常的有丝分裂和胞质分裂，而中心体是由精子带入卵子的。KD卵母细胞的激活触发可能上升的环境和细胞内的pH值后，从性腺释放到海水中产卵。KD卵母细胞胞内钙水平的实时记录表明，pH升高引起异常的Ca 2+爆发，这模仿了受精时发生的Ca 2+爆发。然后，异常的Ca 2+爆发通过钙/钙调素依赖性蛋白激酶（CaMK II）触发减数分裂恢复。因此，PP 2A是必不可少的维持减数分裂停滞和防止孤雌生殖抑制异常Ca 2+爆发产卵。
Unfertilized eggs of most animals are arrested at a certain point in the meiotic cell cycles. Reinitiation of meiosis and the start of embryogenesis are triggered by fertilization. This arrest is essential for preventing parthenogenetic activation and for promoting proper initiation of development by fertilization. In the larvaceanOikopleura dioica, which is a simple model organism for studies of chordate development, the unfertilized egg is arrested at metaphase of meiosis I. We show here that protein phosphatase 2A (PP2A) is essential for maintenance of meiotic arrest after spawning of oocytes. Knockdown (KD) of the maternal PP2A catalytic subunit, which was found in functional screening of maternal factors, caused unfertilized eggs to spontaneously release polar bodies after spawning, and then start pseudo-cleavages without fertilization, namely, parthenogenesis. Parthenogenetic embryos failed to undergo proper mitosis and cytokinesis because of lack of a centrosome, which is to be brought into the egg by a sperm. Activation of the KD oocytes was triggered by possible rise of ambient and intracellular pH upon their release from the gonad into seawater at spawning. Live recording of intracellular calcium level of the KD oocytes indicated that the pH rise caused an aberrant Ca2+burst, which mimicked the Ca2+burst that occurs at fertilization. Then, the aberrant Ca2+burst triggered meiosis resumption through Calcium/calmodulin-dependent protein kinase (CaMK II). Therefore, PP2A is essential for maintenance of meiotic arrest and prevention of parthenogenesis by suppressing the aberrant Ca2+burst at spawning.
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