[Mechanisms of transdifferentiation and their relation to induction and competence]

The ways of transdifferentiation are considered: spontaneous and induced. Spontaneous transdifferentiation taking place after the disaggregation of cells in the clonal and cell cultures is determined by the competence of the transforming cells themselves. Induced transdifferentiation is determined not only by the competence but also by the effect of external inducing factors. It is suggested that the direction of induced transdifferentiation depends on the ratio between the external and internal inducing factors and on the character of cell cycles. It is probable that the inducing factors entering the cells during the early embryonic induction are reproduced in the cells in a dormant state and some of them do not reveal their presence until appropriate conditions are set. When the cells are isolated in the cultures, the ratio of these factors inside the cell changes and a competence to transdifferentiation is revealed which arises as early as during induction.