The cell differentiation in multicellular eukaryotes is one of the most curious phenomena. The recent gene and genome sequencing reveals that most of differentiated cells in a multicellular eukaryote carry a common ge...The cell differentiation in multicellular eukaryotes is one of the most curious phenomena. The recent gene and genome sequencing reveals that most of differentiated cells in a multicellular eukaryote carry a common genome and that such a genome contains the expanded repertoire of genes of proteins associated with the cell-cell adhesion, intercellular and intracellular signal transduction and transcriptional regulation. The cell differentiation occurs in the assembly consisting of a large number of cells after the cell proliferation, and this process is regarded as a stochastic process. Its formulation starts with the master equation in the present paper. The cell differentiation is reproduced in the equation of the most probable path derived from the master equation, when the short-range and long-range interactions between the cells as well as the transition probability between the proliferation and differentiation modes are considered. Moreover, the equation of the most probable path explains the experimental results such as the “memory”, tissue culture and the preparation of induced pluripotent stem (iPS) cells in embryology, if the long-range interaction is considered to be the regulation of gene transcription under the influence of intracellular signal transduction from the receptor accepting the ligand secreted by other types of cells and the short-range interaction is considered to stabilize the intracellular signal transduction by the contact between the same type of cells. The “organizer” found in the initial development of embryo is also explained as the cells that preferentially express the specific gene of a ligand to rouse the long-range interaction. In conclusion, the present study proposes that the complicated intercellular and intracellular signal transduction causing the cell differentiation is ascribed to the long-range interaction between distinctive types of cells and the short-range interaction between the same type of cells.展开更多
Life has been a mystery for most physicists since the question of Maxwell’s demon. In the present paper, the self-reproduction, which is characteristic of the organism, is shown to be essential in resolving the parad...Life has been a mystery for most physicists since the question of Maxwell’s demon. In the present paper, the self-reproduction, which is characteristic of the organism, is shown to be essential in resolving the paradox of Maxwell’s demon. For this purpose, a new thermodynamic quantity of biological activity is introduced to represent the molecular events in an organism recently revealed by molecular biology. This quantity gives a measure that the entropy production arising from the difference between acquired energy and stored energy compensates for the negative entropy of systematizing the organism, and is considered to be proportional to the self-reproducing rate of the organism as the first approximation. The equation of replicator dynamics consisting of self-reproducing rate, death rate and mutation terms contains all known types of evolution of unicellular organisms. When the mutation term is restricted to the point mutation mainly due to the nucleotide base changes in genes, this equation automatically leads to Darwinian evolution that the mutant with the higher increase rate is selected to become prevailing in the population. Throughout this evolution, the nucleotide bases in genes are converged to the special arrangement exhibiting the optimal increase rate of the organism. Moreover, the mutants having experienced gene duplication first decline to the minor members in the population but some of the descendants recover as a new style of organisms by generating new gene(s) from the counterpart of duplicated genes. This evolutionary process to expand the repertoire of genes is mathematically formulated by solving the equation of replicator dynamics up to the higher order of mutation terms. The present theoretical approach can be not only extended to the multicellular diploid eukaryotes but also applied to explain the origin of genes in the self-reproducing proto-cells formed anciently.展开更多
文摘The cell differentiation in multicellular eukaryotes is one of the most curious phenomena. The recent gene and genome sequencing reveals that most of differentiated cells in a multicellular eukaryote carry a common genome and that such a genome contains the expanded repertoire of genes of proteins associated with the cell-cell adhesion, intercellular and intracellular signal transduction and transcriptional regulation. The cell differentiation occurs in the assembly consisting of a large number of cells after the cell proliferation, and this process is regarded as a stochastic process. Its formulation starts with the master equation in the present paper. The cell differentiation is reproduced in the equation of the most probable path derived from the master equation, when the short-range and long-range interactions between the cells as well as the transition probability between the proliferation and differentiation modes are considered. Moreover, the equation of the most probable path explains the experimental results such as the “memory”, tissue culture and the preparation of induced pluripotent stem (iPS) cells in embryology, if the long-range interaction is considered to be the regulation of gene transcription under the influence of intracellular signal transduction from the receptor accepting the ligand secreted by other types of cells and the short-range interaction is considered to stabilize the intracellular signal transduction by the contact between the same type of cells. The “organizer” found in the initial development of embryo is also explained as the cells that preferentially express the specific gene of a ligand to rouse the long-range interaction. In conclusion, the present study proposes that the complicated intercellular and intracellular signal transduction causing the cell differentiation is ascribed to the long-range interaction between distinctive types of cells and the short-range interaction between the same type of cells.
文摘Life has been a mystery for most physicists since the question of Maxwell’s demon. In the present paper, the self-reproduction, which is characteristic of the organism, is shown to be essential in resolving the paradox of Maxwell’s demon. For this purpose, a new thermodynamic quantity of biological activity is introduced to represent the molecular events in an organism recently revealed by molecular biology. This quantity gives a measure that the entropy production arising from the difference between acquired energy and stored energy compensates for the negative entropy of systematizing the organism, and is considered to be proportional to the self-reproducing rate of the organism as the first approximation. The equation of replicator dynamics consisting of self-reproducing rate, death rate and mutation terms contains all known types of evolution of unicellular organisms. When the mutation term is restricted to the point mutation mainly due to the nucleotide base changes in genes, this equation automatically leads to Darwinian evolution that the mutant with the higher increase rate is selected to become prevailing in the population. Throughout this evolution, the nucleotide bases in genes are converged to the special arrangement exhibiting the optimal increase rate of the organism. Moreover, the mutants having experienced gene duplication first decline to the minor members in the population but some of the descendants recover as a new style of organisms by generating new gene(s) from the counterpart of duplicated genes. This evolutionary process to expand the repertoire of genes is mathematically formulated by solving the equation of replicator dynamics up to the higher order of mutation terms. The present theoretical approach can be not only extended to the multicellular diploid eukaryotes but also applied to explain the origin of genes in the self-reproducing proto-cells formed anciently.
