Digit-Type Mechanisms in Cell Differentiation Process: a Theoretical Study

Abstract

According to inductive conception, the interference of neighboring cells causes a production of broken spatial symmetry in an initially homogenous system (cell differentiation process) during embryo development. A concentration gradient of a specific substance (morphogen), which serves as an analog-type control signal, is proposed as an agent to provide this process. It is known fact, that genes’ activity are of a discreet-type (digit) and, therefore, cell differentiation mechanism based on the control digit-type signals in comparison with the analog-type signals is more or less probable. A model presented here simulates the cell differentiation process. The model is based on the assumption that only the digit-type interactions take place between adjacent cells (not analog-type interactions that are typical for the concentration gradient field). Within model assumptions, the genes’ interaction algorithms and boundary condition are postulated. Under the model assumptions, the cell differentiation process starts with the homogeneous blastula formation and comprises three consecutive stages. 1) The loop-like inhomogeneous cell formation development and corresponding set of the self-blocking genes activation - the set of the asymmetric pattern genes governs the process. 2) The line-type inhomogeneous cell formations, with their origins at different cells of the loop-type formation, development and corresponding self-blocking genes activation - the sets of the symmetric pattern genes govern the process. 3) The variety of the function genes activation in the complex inhomogeneous cell formation - the sets of the self-blocking genes govern the process. Under model assumptions the multi level tree-type inhomogeneous cell structures creation is possible. The number of the pattern genes limits the complexity of the inhomogeneous structure. According to the model, in order to provide the further blastula development process, the concentration gradient fields may appear after the initial stages of the cell differentiation process. As simulated by the model, results qualitatively coincide with some of the experimental facts.