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Adult Stem Cells. The Stem Cell Niche. Stem Cell Niche- Defined. A stem cell niche is defined as ‘a specific location in a tissue where stem cells can reside for an indefinite period of time and produce progeny cells while self-renewing’ Self Renewal Asymmetric Division- 1SC 1SC + 1PC
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Adult Stem Cells The Stem Cell Niche
Stem Cell Niche- Defined • A stem cell niche is defined as ‘a specific location in a tissue where stem cells can reside for an indefinite period of time and produce progeny cells while self-renewing’ • Self Renewal • Asymmetric Division- 1SC1SC + 1PC • Populational Asymmetry – 1SC Many Transient Cells. A defined fraction of TC revert to SC; the remainder differentiate
Proposed Niche Types SC Asymmetric Division or Populational asymmetry
Repopulation of Tissue From Stem Cells Cells probably restricted in potential
Signaling in the Drosophila Germarium SC Niche Germarium Stained for Dpp (BMP4) Schematic of germarium showing signaling CPC –Cap Cell IGS-Inner germarium Sheath cells TF- Terminal Filament cells GSC – Germ Stem Cell CB- Cytoblast
Cell-Cell Interactions Mediated by Contact Proteins • Adherens junctions • Cadherin-βCatenin signaling • Gap junctions • direct signals small molecules & ions • Integrins-GAG • Map kinase signaling • ECM • binding and sequestering signal molecules
Some Additional Stem Cell Niches SNO (spindle-shaped N-cadherin-positive osteoblastic) cells