Regeneration is a fundamental attribute of all living things, whether it is simple tissue restoration or the complete replacement of lost body parts such as limbs, tails, or even heads. As a biological problem, regeneration began to be studied formally over 250 years ago in crustaceans by René-Antoine Ferchault de Réaumur (1683-1757), and soon after in hydra by Abraham Trembley (1710-1784). A long-standing problem of biology, regeneration in metazoans still awaits a satisfactory mechanistic explanation. The laboratory's goal is to identify and study the molecular components underpinning this phenomenon. To this end, the researchers have directed their efforts to the study of the diploid planarian Schmidtea mediterranea.

Schmidtea mediterranea is a member of the phylum Platyhelminthes, and is commonly known as a planarian, or flatworm. The uncanny regenerative abilities of these triploblastic animals have been known for many years. Phenomenological studies on planarian regeneration date back to the work of the German naturalist Peter Simon Pallas (1741-1811), and reached its zenith at the turn of the 20th century under the inquisitive minds of Thomas Hunt Morgan (1866-1945) and C. M. Child (1869-1954). For most of the remainder of the century, however, planarians failed to attract the attention of modern molecular biology.

In order to make planarians a more widely used model system, the lab has endeavored to develop the necessary tools to study their biological properties at the molecular level. They have shown that gene expression in these animals can be silenced by double-stranded RNA, and more recently they succeeded in specifically labeling planarian neoblasts -- the stem cell population at the root of the regenerative prowess of these animals. Moreover, they successfully generated several clonal lines of S. mediterranea and have prepared several cDNA libraries for the production of Expressed Sequence Tags (ESTs). To date, the cDNA sequences of close to 4,000 different S. mediterranea genes have been obtained. This EST collection forms part of a web-based database, which will be made freely available to the scientific community in 2001.

Current research in the laboratory involves the creation of transgenic planarians using neoblasts as vectors for the introduction of DNA, as well as a more extensive delineation of the transcription programs activated during the events of metazoan regeneration using DNA microarrays. Altogether, the above tools will allow the researchers to vertically integrate what is learned from planarians into the study of regeneration in higher organisms. Further information on the laboratory's activities can be found at http://www.ciwemb.edu/sanchez.html