Extracellular Ca2+ Is Required for Fertilization in the African Clawed Frog, Xenopus laevis.
Extracellular Ca2+ Is Required for Fertilization in the African Clawed Frog, Xenopus laevis.
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在非洲爪蛙Xenopus laevis中受精需要细胞外Ca2+。
DOI：
10.1371/journal.pone.0170405
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Carlson AE
中科院分区：
文献类型：
--
作者：
Wozniak KL;Mayfield BL;Duray AM;Tembo M;Beleny DO;Napolitano MA;Sauer ML;Wisner BW;Carlson AE
非洲爪蟾（Xenopus laevis）受精和早期胚胎发育过程中细胞外Ca 2+的必要性存在争议。Ca ~（2+）进入X.据报道，顶体反应需要非洲人精子，但已有文献记载，受精和胚胎发育发生在高浓度的Ca 2+螯合剂BAPTA中。在这里，我们试图解决这一争议。利用卵裂沟的出现作为胚胎发育的指标，我们发现X。在缺乏添加的二价阳离子的溶液中授精的羊卵发育正常。相比之下，在毫摩尔浓度的BAPTA或EGTA中授精的卵子未能发育。将精子添加后的胚胎转移到不同的溶液中，我们发现细胞外Ca 2+是精子添加后前30分钟内发生的事件所必需的，但不是之后。我们发现，荧光染色的精子不能穿透在高BAPTA受精卵的包膜，而几个穿透了受精卵的卵黄包膜没有钙螯合剂，或与BAPTA和饱和氯化钙。总之，这些结果表明，受精不会发生在高浓度的Ca 2+螯合剂。最后，我们发现，果冻衣包括>5 mM的容易扩散的Ca 2+。综上所述，这些数据与受精对胞外Ca 2+的需求是一致的。根据我们的研究结果，我们假设，围绕鸡蛋的果冻外套作为一个储备容易获得的Ca 2+离子，以促进受精在不断变化的细胞外环境。
The necessity of extracellular Ca2+ for fertilization and early embryonic development in the African clawed frog, Xenopus laevis, is controversial. Ca2+ entry into X. laevis sperm is reportedly required for the acrosome reaction, yet fertilization and embryonic development have been documented to occur in high concentrations of the Ca2+ chelator BAPTA. Here we sought to resolve this controversy. Using the appearance of cleavage furrows as an indicator of embryonic development, we found that X. laevis eggs inseminated in a solution lacking added divalent cations developed normally. By contrast, eggs inseminated in millimolar concentrations of BAPTA or EGTA failed to develop. Transferring embryos to varying solutions after sperm addition, we found that extracellular Ca2+ is specifically required for events occurring within the first 30 minutes after sperm addition, but not after. We found that the fluorescently stained sperm were not able to penetrate the envelope of eggs inseminated in high BAPTA, whereas several had penetrated the vitelline envelope of eggs inseminated without a Ca2+ chelator, or with BAPTA and saturating CaCl2. Together these results indicate that fertilization does not occur in high concentrations of Ca2+ chelators. Finally, we found that the jelly coat includes >5 mM of readily diffusible Ca2+. Taken together, these data are consistent with requirement of extracellular Ca2+ for fertilization. Based on our findings, we hypothesize that the jelly coat surrounding the egg acts as a reserve of readily available Ca2+ ions to foster fertilization in changing extracellular milieu.