Arata Yukinobu, Takagi Hiroaki, Sako Yasushi, Sawa Hitoshi
Laboratory for Cell Fate Decision, Center for Developmental Biology, RIKEN Hyogo, Japan ; Cellular Informatics Laboratory, RIKEN Saitama, Japan.
Department of Physics, School of Medicine, Nara Medical University Nara, Japan.
Front Physiol. 2015 Jan 28;5:529. doi: 10.3389/fphys.2014.00529. eCollection 2014.
Cell size is a critical factor for cell cycle regulation. In Xenopus embryos after midblastula transition (MBT), the cell cycle duration elongates in a power law relationship with the cell radius squared. This correlation has been explained by the model that cell surface area is a candidate to determine cell cycle duration. However, it remains unknown whether this second power law is conserved in other animal embryos. Here, we found that the relationship between cell cycle duration and cell size in Caenorhabditis elegans embryos exhibited a power law distribution. Interestingly, the powers of the time-size relationship could be grouped into at least three classes: highly size-correlated, moderately size-correlated, and potentially a size-non-correlated class according to C. elegans founder cell lineages (1.2, 0.81, and <0.39 in radius, respectively). Thus, the power law relationship is conserved in Xenopus and C. elegans, while the absolute powers in C. elegans were different from that in Xenopus. Furthermore, we found that the volume ratio between the nucleus and cell exhibited a power law relationship in the size-correlated classes. The power of the volume relationship was closest to that of the time-size relationship in the highly size-correlated class. This correlation raised the possibility that the time-size relationship, at least in the highly size-correlated class, is explained by the volume ratio of nuclear size and cell size. Thus, our quantitative measurements shed a light on the possibility that early embryonic C. elegans cell cycle duration is coordinated with cell size as a result of geometric constraints between intracellular structures.
细胞大小是细胞周期调控的关键因素。在非洲爪蟾胚胎的中囊胚转换（MBT）之后，细胞周期时长与细胞半径的平方呈幂律关系延长。这种相关性已由细胞表面积是决定细胞周期时长的候选因素这一模型得到解释。然而，这种二次幂律在其他动物胚胎中是否保守尚不清楚。在这里，我们发现秀丽隐杆线虫胚胎中细胞周期时长与细胞大小之间的关系呈现幂律分布。有趣的是，根据秀丽隐杆线虫的原始细胞谱系，时间 - 大小关系的幂次可分为至少三类：高度大小相关、中度大小相关以及可能的大小不相关类别（半径分别为1.2、0.81和<0.39）。因此，幂律关系在非洲爪蟾和秀丽隐杆线虫中是保守的，而秀丽隐杆线虫中的绝对幂次与非洲爪蟾中的不同。此外，我们发现在大小相关类别中，细胞核与细胞之间的体积比呈现幂律关系。在高度大小相关类别中，体积关系的幂次最接近时间 - 大小关系的幂次。这种相关性增加了一种可能性，即至少在高度大小相关类别中，时间 - 大小关系是由细胞核大小与细胞大小的体积比来解释的。因此，我们的定量测量揭示了一种可能性，即由于细胞内结构之间的几何约束，秀丽隐杆线虫早期胚胎的细胞周期时长与细胞大小是协调的。
