Expression of en in the Prosencephalon Heterotopically Transplanted into the Mesencephalon

The alar plate of the prosencephalon differentiates into a tectum-like structure when transplanted and integrated into the mesencephalon around 10-somite stage. Homeobox containing gene, en , is expressed in the mesencephalon with caudorostral gradient from 7-somite stage. Here expression of en in the prosencephalic transplant in the mesencephalon was studied immunohistochemically with anti- en antibody. Transplantation was carried out between quail and chick. It was shown that the transplant was stained with anti- en antibody at the caudal part of the mesencephalon. At the rostral part, the transplant did not express en . When the transplant was not contiguous to the caudal part of the host mesencephalon, it did not express en . The present study suggests that the prosencephalic transplant differentiates into the tectum-like structure when it expresses en at the caudal part of the mesencephalon.