UNIVERSITY OF PUERTO RICO
Gene profiling of nervous system regeneration using a novel model organism Post-traumatic regeneration of neurons and fibers in the mammalian spinal cord has not been plausible, even though extensive studies have been made to understand the restrictive factors involved. New experimental strategies are necessary to try and solve a problem that in humans causes great emotional, physical and financial burdens. One such strategy is the comparative analysis between animals capable of regenerating their CNS and those where CNS regeneration is restricted, in order to identify the molecules and mechanisms that allow for CNS regeneration. We have recently shown that holothurians are capable of rapid and complete regeneration of the main component of their CNS, the radial nerve cord. Regeneration involves both the outgrowth of nerve fibers and formation of new neurons through proliferation and/or transdifferentiation of glial cells. Moreover, the regenerated tissue looks similar at the cellular level to the remaining nerve cord. We propose to use this model system to (1) generate cDNA libraries of normal and regenerating nerve cord, and create an EST database of the transcripts found within the tissues, (2) do in silico differential display to determine putative genes that are differentially expressed during regeneration and (3) perform microarray analyses to determine those genes whose expression is modified during nerve regeneration. Inherent in this proposal is the notion that in order to study the molecular basis of regenerative processes we must focus on the appropriate model system. Classical models of molecular genetics such as Drosophila and C. elegans have limited regenerative potential. On the other hand, hydra and planarians, the animals, which have been traditionally used in regeneration studies, are too distant from vertebrates to have an immediate impact on therapeutic strategies. Holothurians with their striking regeneration capabilities provide a perfect model for this analysis, plus the additional benefit that being deuterostomes they are phylogeneticaly closer to vertebrates. Thus, in the same way that Drosophila and C. elegans have provided important information to the field of developmental biology, holothurians can be the source of key information to advance the field of nerve regeneration and neurogenesis far beyond its present status. The outcome of our experiments will be the identification of genes involved in nerve cord regeneration. These will include genes that are over-expressed during the process and possibly code for molecules that induce the regeneration process, and genes that are under-expressed during the process and might code for some substances that repress the regeneration process and thus their inhibition could aid regeneration. The identification of these genes is the first step in understanding the processes that allow for dramatic nervous system regeneration in an animal group that is a close relative of vertebrates. PUBLIC HEALTH RELEVANCE: Can we learn from other animals how to regenerate our nervous system? This is the long term aim of this research proposal where we focus on an animal with amazing regenerative properties, the sea cucumber. We will use this animal to determine the gene activation profile during nerve cord regeneration and therefore identify genes that might be of importance for human nervous system regeneration.