Principal Investigator Peter Reddien
The hallmark attributes of stem cells are the capacity for self-renewal and the ability to produce one or more differentiated cell types. We aim to understand these stem cell features by study of planarian neoblasts. Planarians are full of neoblasts, the neoblasts are regulated by contextual cues (wounding, growth, homeostatic replacement of aged cells), and the neoblasts are capable of replacing essentially every cell type in the animal. This rich stem cell biology can now be studied with our emerging tools: we can inhibit any gene desired and assess the effects on neoblasts in vivo, we can isolate >100,000 neoblasts in a day by flow cytometry, and assays exist for assessing neoblast differentiation. Together, these neoblast attributes and tools present a powerful new approach to stem cell biology.
Because neoblast-expressed genes have a recognizable pattern of expression in whole-mount in situ hybridizations, it has been possible to identify many neoblast-expressed genes and to study their function with RNAi. For example, a SMEDWI-2 (PIWI-like) protein was required for neoblast progeny function and numerous other genes are required for neoblast maintenance. Neoblasts normally divide during homeostatic maintenance of the body and respond to wounds to result in an increase in numbers of mitotic cells. We are also utilizing our RNAi-screening approach to identify genes involved in this process of regeneration initiation.