Roles of Pax-2 in initiation of the chick tectal development

Brain Res Dev Brain Res. 1999 Aug 5;116(1):41-9. doi: 10.1016/s0165-3806(99)00073-5.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Chick Embryo / growth & development
  • Chick Embryo / metabolism*
  • Cloning, Molecular
  • DNA-Binding Proteins / genetics*
  • Diencephalon / embryology
  • Diencephalon / metabolism
  • Gene Expression Regulation, Developmental / physiology*
  • Mesencephalon / embryology
  • Mesencephalon / metabolism
  • Molecular Sequence Data
  • PAX2 Transcription Factor
  • Sequence Homology, Amino Acid
  • Superior Colliculi / embryology
  • Superior Colliculi / metabolism*
  • Transcription Factors / genetics*
  • Transformation, Genetic


  • DNA-Binding Proteins
  • PAX2 Transcription Factor
  • Transcription Factors