Gbx2 homeobox genes are important for formation and function of the midbrain/hindbrain boundary, namely the isthmic organizer. Two Gbx2 genes were identified in Xenopus laevis, differing in 13 amino acids, including a change in the homeodomain. Xgbx2a is activated earlier during gastrulation and reaches higher levels of expression while Xgbx2b is expressed later, at lower levels and has an additional domain in the ventral blood islands. Their overexpression results in microcephalic embryos with shortened axes and defects in brain and notochord formation. Both genes encode functionally homologous proteins, which differ primarily in their temporal and spatial expression patterns.
Bibliographical noteFunding Information:
We thank Dr. Dale Frank and Dr. Oded Khaner for discussions during the course of the work. This work was supported in part by grants from the March of Dimes Birth Defects Foundation, Volkswagen Stiftung and The Israel Academy of Sciences to A.F. and by the Sheinbrun Foundation to Y.G.
- Anterior-posterior axis
- Embryonic development
- Isthmic organizer
- Midbrain-hindbrain boundary