Physics underling Topobiology: Space-time Structure underlying the Morphogenetic Process

Development processes of multi-cellular systems have attracted attention for a long time. One particular aspect of interest is the fusion of the symmetric and asymmetric cell divisions in space. We clarify the physical principle for determining whether asymmetric cell divisions occur in living beings or not. Then, we also reveal the physical reason why the organs such as arms, legs, lungs, vertebrae, and kidneys are left-right symmetric, while the heart and the liver are asymmetric. Next, we examine the temporal aspects underlying the morphogenetic processes. The macroscopic model having six categories of molecules shows that the antagonism between the negative controllers and the positive replication factors induces bifurcations in stem and pluripotent cells at rhythmic intervals comprising about six divisions. This cycle of six divisions, i.e., branching time between periodic bifurcation events, corresponds to the emergence timings of blast cysts, embryos, germ layers, tissues, and organs, which can be observed for about every six cell divisions. Finally, we show that the evolution of negative controllers brings longer non-coding regions in DNA and higher-organisms.