S19-05 Regulation of muscle stem cell fate by Pax genes

Regeneration is a trait observed in various metazoans to differing extents. We are interested in how some species manage to regenerate complex structures and why this ability has been lost in other species. Among vertebrates, the salamanders have the most impressive regenerative abilities that includes appendage and spinal cord regeneration as well as regeneration of a number of organs such as the heart. An important question is to what extent cells revert to a primitive embryonic state in order to restart the process of regenerating a complex structure such as the limb or tail. Do cells become multior pluri-potent? Having developed germline transgenesis in this animal, we are able to track different cell types during limb and tail regeneration. From such studies, we show that cells do not become pluripotent during limb regeneration but rather display properties of tissuerestricted progenitors probably similar to those present in the limb bud. In the spinal cord, we present evidence that spinal cord amputation causes cells revert to an embryonic neuroepitheliallike state in order to restart spinal cord growth.