1. Nara Institute of Science and Technology Graduate School of Biological Sciences 8916-5, Takayama, Ikoma, Nara, 630-0101 Japan
2. Max-Planck Institute for Brain Research, Deutschordenstr. 46, 60528 Frankfurt/M., Germany
3. These authors contributed equally to this work.

Correspondence to: Toshihiko Ogura¹ Correspondence and requests for materials should be addressed to T.O. (e-mail: Email: ogura@bs.aist-nara.ac.jp).

Abstract

Much progress has been made in understanding limb development^{1, 2, 3}. Most genes are expressed equally and in the same pattern in the fore- and hindlimbs, which nevertheless develop into distinct structures^{3, 4, 5, 6, 7, 8}. The T-box genes Tbx5 and Tbx4, on the other hand, are expressed differently in chick wing (Tbx5) and leg (Tbx4) buds^{9, 10, 11, 12}. Molecular analysis of the optomotor blind gene¹³, which belongs to the same family of transcription factors, has revealed that this gene is involved in the transdetermination of Drosophila wing and leg imaginal discs¹⁴. In addition, expression of Tbx5 and Tbx4 correlates well with the identity of ectopic limb buds induced by fibroblast growth factor⁴,⁵,^{15, 16, 17, 18, 19}. Thus, it is thought that Tbx5 and Tbx4 might be involved in determining limb identity. Another candidate is the Pitx1 gene, which encodes a bicoid-type homeodomain transcription factor that is expressed in leg buds²⁰,²¹. Here we determine the importance of these factors in establishing limb identity.

1. Nara Institute of Science and Technology Graduate School of Biological Sciences 8916-5, Takayama, Ikoma, Nara, 630-0101 Japan
2. Max-Planck Institute for Brain Research, Deutschordenstr. 46, 60528 Frankfurt/M., Germany
3. These authors contributed equally to this work.

Correspondence to: Toshihiko Ogura¹ Correspondence and requests for materials should be addressed to T.O. (e-mail: Email: ogura@bs.aist-nara.ac.jp).