Peter W. Reddien, PhD

Member, Whitehead Institute Assistant Professor of Biology, MIT Howard Hughes Medical Insitute Early Career Scientist 617.324.4083 phone reddien@wi.mit.edu

Regeneration of tissues and organs is one of the great unsolved mysteries of biology. Whitehead Member Peter W. Reddien works to shed light on that mystery through research on the planarian Schmidtea mediterranea, a flatworm with regenerative powers that have captured the imagination of biologists for more than a century.

Planaria can reproduce either sexually or asexually. Asexual animals reproduce by dividing into two, with both head and tail fragments regrowing into complete animals. All planaria also can accomplish this feat if cut into two surgically. New tissues and organs are created by neoblasts—adult stem cells that share certain characteristics with embryonic stem cells and can differentiate into essentially all cells found in adult animals. A similar process occurs in normal intact adults, in which neoblast progeny cells continually replace aged cells. Additionally, if nutrition is limited, planaria can exhibit “de-growth”—eliminating cells while maintaining the form and function of the various organ systems of the animals. The genetic and molecular mechanisms underlying these capabilities are almost completely unknown.

Reddien is working to create a body of knowledge and research tools that will establish the planarian as a model organism with which to study the molecular genetics of regeneration. (The classic invertebrate model organisms, the Drosophila fruit fly and C. elegans worm, cannot efficiently regenerate tissues as adults.) He and co-workers recently developed methods for high-throughput RNA interference (RNAi), which employs customized RNAs to silence production of proteins from a given gene. Exploiting these methods, Reddien then led the first large-scale study of gene function in planaria, discovering multiple genes needed for regeneration.

In addition to tackling the challenges of regeneration, his work should aid a more general understanding of stem cells. Recently, Reddien’s lab discovered that the gene Smed-beta-catenin-1 is crucial in determining head-to-tail polarity–whether a planarian, when cut, will produce a head or tail at a particular site.  These findings could help to explain how regenerating animals “know” which missing tissues to make.

Selected Publications

Christian P. Petersen and Peter W. Reddien. 2008. Smedbetacatenin-1 is required for anteroposterior blastema polarity in planarian regeneration. Science. Jan 18;319(5861):327-30.

Peter W. Reddien, Adam L. Bermange, Adrienne M. Kicza, Alejandro Sanchez Alvarado. 2007. BMP signaling regulates planarian midline specification and is needed for asymmetric regeneration.  Development, 134: 4043-4051.

Peter W. Reddien, Néstor J. Oviedo, Joya R. Jennings, James C. Jenkin, and Alejandro Sánchez Alvarado. 2005. SMEDWI-2 is a PIWI-like protein that regulates planarian stem cells for regeneration and homeostasis. Science 310: 1327-1330.

Reddien PW, Bermange AL, Murfitt KJ, Jennings JR, Sánchez Alvarado A. 2005. Identification of genes needed for regeneration, stem cell function, and tissue homeostasis by systematic gene perturbation in planaria. Dev Cell. 8(5):635-49.

Reddien PW, Sánchez Alvarado A. 2004. Fundamentals of planarian regeneration. Ann. Review Cell and Dev. Bio. 20: 735-757.

Newmark PA, Reddien PW, Cebria F, Sánchez Alvarado A. 2003. Ingestion of bacterially expressed double-stranded RNA inhibits gene expression in planarians. Proc Natl Acad Sci 100 Suppl 1:11861-5.

[lab]

[research summary]

[publications (pubmed database)]