Meeting Abstract

13.3  Sunday, Jan. 4  A long-term somite fate map using GFP-transgenic axolotls PIEKARSKI, N.*; OLSSON, L.; Friedrich-Schiller-Universitaet Jena, Germany; Friedrich-Schiller-Universitaet Jena, Germany nadine.piekarski@uni-jena.de

Derivatives of single somites are well studied using quail-chick chimeras. In order to investigate comparative aspects of single somite fate, we have extended this work to a urodele amphibian, the Mexican axolotl. Such an approach might enhance our knowledge of how conserved somite fate is, despite drastic differences in anatomy. Skeletal elements, such as the occipital region and the shoulder girdle in the axolotl, are anatomically quite different compared to the chicken, and of special interest for us. Both receive contributions from the somites in quail-chick chimeras. We focused on skeletal and muscular derivatives of somites two to six in the axolotl, which we determined using two different techniques. One technique was injections of dextran-fluorescein into the central part of single somites and detection of the marker in young larvae on paraffin sections using immunofluorescence. The other was transplantations of single somites using GFP-transgenic axolotls. Transplanted GFP-fluorescent somites and their derivatives could be tracked in vivo, and for a better evaluation cryosections were made. Our results demonstrate a very similar origin for the shoulder girdle, or more precisely the scapula, in quail-chick chimeras and axolotl. Thus in both species the shoulder girdle develops in a composite (somites and lateral plate) and segmental (more than one somite) fashion, but with differences in the number of participating somites and in the position of the border between lateral plate and somite derived cells. We postulate that the relative position of the shoulder girdle during development is crucial for these differences in somitic contributions.