Journal Club 1-4

• Shackleton M, F Vaillant, KJ Simpson, J Stingl, GK Smyth, ML Asselin-Labat, L Wu, GJ Lindeman, JE Visvader. Generation of a functional mammary gland from a single stem cell. Nature 2006 Jan 5, 439 (7072): 84-8
  Enriched mammary repopulation unit (MRU) was found in CD24+CD29hiLin- (CD45-,Ter119-,CD31-), where CD29 is integrin Beta1. CD49, aka integrin alpha-6, population was enriched in those population. Interestingly, Clarke group used CD24-/lo CD44+ as markers for human MaSC, that was verified by serial xenograft experiments. It was also a surpise that CD24+CD29hiLin- cells are not side population, nor Sca1+, though Wicha group identified human MaSC by using side population. Transplant data show the repopulation/differentiation potential of those cells.
  Only few CD24+CD49hiLin- cells were not found expression of Keratin 18 or Keratin 14. In vitro metrigal experiment further confirmed increased progenitor capaticty of those cells.
  With a refined protocol of double sorting, viability confirmation, outgrowth rate incresed from 1/590 to 1/64. LacZ labeled single cell transplantation data show those cells are able to repopulate mammary fat pad (MFP) without supporting cells at rate of 8 outgrowths out of 68. The authors argue it would be unlikely outgrowth was derived from multiple progenitor cells. However, it would need barcode system, that individually label each cell. Further mixing experiment data demonstrate about total 70 cells of mixed LacZ and WT mice could repopulate MFP at a rate of 97/112, in which 95 out 97 of the MFP were from either WT or LacZ. The tertiary transplant data suggest selfrenewal of those cells. Interestingly, tranplanted MFP has higher percentage of CD24+CD49hi population.
  In the mice prone to tumor development, CD24+CD49hiLin- subpopulation was found expanded in MMTV-Wnt premalignant tissue, but not in MMTV-neu mice that develp luminal epithelial tumor.
  
• Stingl J, P Eirew, I Ricketson, M Shackleton, F Vaillant, D Choi, HI Li, CJ Eaves. Purification and unique properties of mammary epithelial stem cells. Nature 2006 Jan 4,
  Mixing experiment with CFP and GFP mice shows single progenitor/stem cell is able to generate MFP, that was further cofirmed by Serial diluation data with 75 cells to 20 cells transplantation. CD49f instead of CD29 was used as marker, while the Lin- and CD24+ were shared with previous report. CD24highCD49flow (Ma-CFC-enriched), CD24medCD49fhigh (MRU-enriched), CD24lowCD49flow (MYO) were identified as subpopulations of special lineage potential. Dye efflux and cell cyle properties were elucidated in those cels.
  
• Al-Hajj M, MS Wicha, A Benito-Hernandez, SJ Morrison, MF Clarke. Prospective identification of tumorigenic breast cancer cells. Proc Natl Acad Sci U S A 2003 Apr 1, 100 (7): 3983-8
  
• Dontu G, WM Abdallah, JM Foley, KW Jackson, MF Clarke, MJ Kawamura, MS Wicha. In vitro propagation and transcriptional profiling of human mammary stem/progenitor cells. Genes Dev 2003 May 15, 17 (10): 1253-70