Institute for Biogenesis Research, John A Burns School of Medicine, University of Hawaii at Manoa, HI 96822, USA.
Syst Biol Reprod Med. 2011 Feb;57(1-2):43-9. doi: 10.3109/19396368.2010.505679. Epub 2011 Jan 5.
Reproductive biology is considered a specialty field, however, an argument can be made that it is instead generally applicable to many fields of biology. The one-cell embryo is presented here as a model system for the study of eukaryotic DNA replication, apoptotic DNA degradation, and signaling mechanisms between the cytoplasm and nucleus. Two unique aspects of this system combine to make it particularly useful for the study of chromatin function. First, the evolutionary pressure that lead to the extreme condensation of mammalian sperm DNA resulted in a cell with virtually inert chromatin, no DNA replication or transcription ongoing in the sperm cell, and all of the cells in a G(0) state. This chromatin is suddenly transformed into actively transcribing and replicating DNA upon fertilization. Therefore, the sperm chromatin is poised to become active but does not yet possess sufficient components present in somatic chromatin structure for all these processes. The second unique aspect of this system is that the one cell embryo houses two distinct nuclei, termed pronuclei, through the first round of DNA synthesis. This means the sperm cell can be experimentally manipulated to test the affects of the various treatments on the biological functions of interest. Experimental manipulations of the system have already revealed a certain level of plasticity in the coordination of both the timing of DNA synthesis in the two pronuclei and in the response to cellular signals by each pronucleus involved with the progression through the G1/S checkpoint, including the degradation of DNA in the paternal pronucleus. The fact that two nuclei in the same cytoplasm can undergo different responses infers a level of autonomy in the nuclear control of the cell cycle. Thus, the features of mammalian fertilization can provide unique insights for the normal biology of the cell cycle in somatic cells.
生殖生物学被认为是一个专业领域，但也有人认为它实际上适用于许多生物学领域。本文以单细胞胚胎为模型系统，研究真核生物 DNA 复制、凋亡 DNA 降解以及细胞质和细胞核之间的信号转导机制。这个系统有两个独特的方面，使其特别适合研究染色质功能。首先，导致哺乳动物精子 DNA 极度浓缩的进化压力导致精子细胞的染色质几乎没有活性，精子细胞中没有 DNA 复制或转录，并且所有细胞都处于 G0 状态。这种染色质在受精后突然转变为活跃转录和复制的 DNA。因此，精子染色质准备好变得活跃，但还没有获得体细胞染色质结构中存在的所有这些过程所需的足够成分。该系统的第二个独特方面是，在第一轮 DNA 合成过程中，单细胞胚胎中存在两个不同的核，称为原核。这意味着可以对精子细胞进行实验操作，以测试各种处理对感兴趣的生物学功能的影响。该系统的实验操作已经揭示出，在两个原核中 DNA 合成的时间以及每个原核对 G1/S 检查点的细胞信号的反应的协调方面存在一定程度的可塑性，包括父原核中 DNA 的降解。同一细胞质中的两个核可以做出不同反应这一事实暗示了细胞核对细胞周期的控制具有一定程度的自主性。因此，哺乳动物受精的特征可以为体细胞细胞周期的正常生物学提供独特的见解。
