Membrane Impression and Gene Expression

The central question in the molecular biology of differentiation is: why are new parts of the genome transcribed? Different hypotheses have been suggested for the control of the cytodifferentiation process. Many of these postulate a "time programme"; others postulate a "programme of events", leading to the conversion of cells to new phenotypes. In the model discussed here the fatter postulate is favoured, suggesting that the differentiation process is guided by the continuous and sequential changes of the microenvironment of the cell. The knowledge of the regularity of these changes is integrated as "evolutive experience", as a more or less fixed programme into the genome. Specific structures in the cell membrane (receptors, receptor areas) are able to perceive and transduce the signal of the environment. The signal can be transformed and regulated in the cell on different levels. For this process—the information flux from the cell membrane to the genome—the term " membrane impression " is proposed in contrast to the information flux from the genome to the cell membrane " gene expression ". It is mentioned that the differentiation process corresponds to the alternative interaction between the cell membrane and the genome. This typical Ping Pong interaction results in cell lineage. It is postulated that membrane receptors for the next anticipated signals are coexpressed with a specific phenotype of the cell. The possibility of the existence of different receptors is discussed.