Volume 1, 2000
March 7, 2000
Copyright © 2000 by Mary Ann Liebert, Inc.
The Case for Comparative Regeneration: Learning from
Simpler Organisms How to Make New Parts from Old
ALEJANDRO SÁNCHEZ ALVARADO, Ph.D.
Regeneration is a primordial attribute of all living organisms, and as a biological problem
it has attracted the attention of generations of experimental biologists for almost 300 years.
Yet regeneration still awaits a satisfactory mechanistic explanation. In this brief review, I
will argue for the reinstatement of planarians, a classical and currently understudied ex-
perimental organism, as a viable, molecular model system in which to functionally dissect
the molecular basis of animal regeneration. The developmental plasticity and phylogenetic
position of planarians, coupled with the technical ability to specifically silence gene expres-
sion via RNA interference should help usher these organisms to the forefront of regenera-
tion research. Planarians are currently in a unique position to provide us with the funda-
mental tools required to begin the identification and functional characterization of the genetic
interactions operating behind the regenerative abilities found in the metazoans.