Roles of Pax-2 in initiation of the chick tectal development.
Transplantation experiments have shown that the mes-metencephalic boundary (isthmus) acts as an organizer for the development of the optic tectum. We have cloned Pax-2 which is expressed in the isthmus. Previously it was shown that Pax-5, a member of the same Pax subfamily as Pax-2, transformed the diencephalon into a tectum-like structure and induced isthmus- and tectum-related genes both in the mesencephalon and in the diencephalon. In order to define the distinct roles between Pax-2 and Pax-5 in development of the tectum, we expressed Pax-2 ectopically in the mesencephalon and the diencephalon of E2 chick embryos by in ovo electroporation. Histological observation demonstrated that Pax-2 transformed the diencephalon into a tectum-like structure. In Pax-2, transfected embryos the expression of isthmus- and tectum-related genes such as Fgf8 and En-2 was induced in the diencephalon. However, neither Fgf8 nor En-2 expression was induced in the mesencephalon, making a striking contrast with the result of Pax-5 misexpression. In E2 chick embryos, the mesencephalon is committed of its fate to differentiate into the tectum, but the diencephalon has plasticity on its fate. Moreover, Pax-2 expression in the isthmus precedes Pax-5 expression. Taking these results into consideration, it is suggested that Pax-2 plays a crucial role in initiation of the tectal development, and that Pax-5 functions to maintain the state of tectal differentiation.
Okafuji
T
T
Department of Molecular Neurobiology, Institute of Development, Aging and Cancer (IDAC), Tohoku University, Seiryo-machi 4-1, Aoba-ku, Sendai, 980-8575, Japan.
Funahashi
J
J
Nakamura
H
H
D000595:Amino Acid Sequence; D000818:Animals; D002642:Chick Embryo / Q000254:growth & development / Q000378:metabolism*; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics*; D004027:Diencephalon / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008636:Mesencephalon / Q000196:embryology / Q000378:metabolism; D008969:Molecular Sequence Data; D051762:PAX2 Transcription Factor; D017386:Sequence Homology, Amino Acid; D013477:Superior Colliculi / Q000196:embryology / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics*; D014170:Transformation, Genetic
D004268:DNA-Binding Proteins; D051762:PAX2 Transcription Factor; D014157:Transcription Factors