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1/18/17Introduction to Stem CellsKey Features of Stem CellsStem cells – a cell that can divide to give rise to both a new copy of itself and at least one specialized, differentiated, cell typePluripotency – ability to differentiate into most cell typesoSpectrum of potency states:Totipotent – able to form all cell types of the embryo and the adult, including germ cells and non-embryonic structures connected to the fetusPluripotent – can do all of these things but is not able to form the non-embryonic structuresMultipotent – able to form many but not all tissue cells of the body, can only form those cell types in the organs or tissue of the body in which they are normally locatedAll other stem cells found in specialized tissue of the fetus or adultUnipotent – able to form just one other cell typeTerminally differentiated – a specialized cell that produces all of the proteins required forits proper function within the tissue or organ it belongs toCan at best divide only a few times, but more often not at allSelf-renewal – cells are capable of replicating and proliferating extensively without changing stateStem Cell Division Patterns: Self-RenewalAsymmetric vs symmetricAll lines must relate back to one stem cellAll lines must result in some cells remaining undifferentiated stem cellsGeneral Stem Cell PropertiesPluripotencySelf-renewalClonality – ability to generate a population of stem cells from a single progenitor cell (this is a difficult concept to prove)Expression of characteristics transcription factors/molecular markersMachinery for rapid cell cycle progressionoG1 period occurrence – done very quickly allowing rapid proliferation of cellsMachinery for telomere maintenanceoStem cells can fill out the end of the chromosome (the telomere – protective caps for the chromosomes)After cell division, these caps are shortened and once they are used up errors can occur leading to death of the cellThe shorter the telomere, the “older” the celloThis means that stem cells have a high amount of telomerase activityCapacity to sense and respond to a wide variety of cell signaling systems (TGF-B, wnt, etc.)oSignals between neighboring cells as well as those cells that are far away1/20/17Introduction to Envisioned Stem Cell Usesnew cell lines for research and testing drugsoindefinite cell growth in the laboit is not easy to create immortal lines, usually the primary cells will begin to die after a finite amount of time/divisions
oimmortal = cells must be transformeddone via either harvesting tumor cells or harvesting primary cells and treating them withsomething to transform them (virus, oncogene)osome cell types are very hard to immortalize or harvest or even grow in a lab settingstem cells bridge this problemnew models to discover cell defects that underlie human genetic diseaseowant to know what, mechanistically, went wrong to cause genetic diseaseso