Do CNS anlagen have plasticity in differentiation? Analysis in quail-chick chimera.

Heterotopic transplantations of brain vesicles of a quail embryo into a chick embryo were carried out in order to elucidate if CNS anlagen have plasticity in differentiation at the 7-10 somite stage. Quail cells are distinguished from chick cells due to the difference in nuclear morphology. The prosencephalon did not differentiate into the cerebellum when transplanted into the metencephalon, although previous study showed that the prosencephalon has the capacity to differentiate into the optic tectum. The mesencephalon differentiated as an optic tectum when transplanted into the prosencephalon or into the rhombencephalon. The metencephalon differentiated as a cerebellum in the telencephalon. It is concluded that only the prosencephalon has limited plasticity, but the mesencephalon and rhombencephalon are determined by the 7-10 somite stage.