Meeting Abstract

P2.97  Monday, Jan. 5  Limb specification and growth initiation in Xenopus laevis: Possible heterochronic mechanisms CARRENO, C. A.**; SMITH, K. K.; Duke University, Durham, NC; Duke University, Durham, NC carrie.carreno@duke.edu

In most vertebrates, the fore and hind limbs arise nearly synchronously, early in development. In anurans, however, the hindlimbs appear before the forelimbs. Further, limb development occurs late in the developmental period, well into the free-swimming larval stage and well after the body plan and major organ systems are established. In vertebrates, early limb patterning is generally understood. The identity of the forelimb is through Tbx5, whereas Pitx1 and Tbx4 identify the hindlimb. The feedback loop between Fgf10 and Fgf8 regulates the initiation and outgrowth of both fore and hind limbs, and their area of expression is restricted to the hindlimb field by Wnt8 and to the forelimb field by Wnt2. Compared to other vertebrates, little is known about the development of the limbs in anurans. We have cloned the genes mentioned above from Xenopus laevis and we are using whole-mount in situ hybridization to observe patterns of expression during specification of the limb fields and the initiation of limb growth in late stage embryos (tadpoles). By comparing patterns of expression, we can identify heterochrony in gene expression and understand the developmental mechanism that may be responsible for the asynchrony of limb development in anurans.