17 Fate Mapping of Stem Cells

Abstract

STEM CELL FATE MAPPING: GENERAL CONSIDERATIONS
To discuss stem cell “fate,” a working definition of a stem cell must be utilized. For the purposes of this discussion, a practical definition is a cell with the capacity for prolonged or unlimited self-renewal, combined with the capacity to produce at least one type of highly differentiated progeny. In the context of that definition, the term “stem cell fate mapping” implies that a stem cell has a specific fate that can be discovered in experimental systems directed toward fate mapping, and once discovered, the same fate can be extrapolated to other stem cells of that type. Short of the ultimate common fate of cell death, however, stem cells may have widely variable fates depending on the parameters and conditions imposed by the mapping system. This is one of the current challenges to our understanding of stem cell biology, and a primary source of controversy regarding the identity and potential of specific stem cells. There is increasing evidence for remarkable plasticity in some stem cells even when derived from adult tissues. To cite one of many recent examples, it appears that hematopoietic stem cells give rise to muscle under circumstances of muscle injury or disease (Ferrari et al. 1998; Gussoni et al. 1999). A few years ago, this would have been heretical based on data from previously utilized fate mapping systems. It is clear that as new fate mapping systems are utilized, the currently accepted map for many stem cell candidate populations may need...