Summary of Research Project Results under JSPS FY2004
"Research for the Future Program"

1. Research Institution   The University of Tokyo
2. Research Area Life Sciences
3. Research Field Development, Differentiation, and Regeneration
4. Term of Project FY 2000 - FY 2004
5. Project Number 00L01501
6. Title of Project Establishment of Cell and Organ Transplantation Therapy Using Embryonic and Somatic Stem Cells

7. Project Leader

Name Institution, Department Title of Position
Nobuaki, Yoshida The University of Tokyo, The Institute of Medical Science professor

8. Core Members

Names Institution, Department Title of Position
Hiromitsu, Nakauchi The University of Tokyo, The Institute of Medical Science professor
Ryuichi, Nishinakamura The University of Tokyo, The Institute of Medical Science associate professor

9. Summary of Research Results

Rex-1 is one of the marker genes for undifferentiated ES cells whose expression is controlled by Oct-3/4 and unknown transcription factor named Rox-1. We identified Rox-1 as PTB (polypyrimidine tract binding protein). PTB null mice die around the stage of implantation and ES cells are not recovered from the blastocyats of these mice so far. The attempt to establish PTB null ES cells using Cre/loxP system in vitro has revealed the reduced growth rate in these cells when compared to wild-type ES cells.
This result indicates the important roles of Rox-1 both in ES cell growth/self-renewal and in early mouse development.
To clarify the role of each component of PcG complex in HSCs, we performed loss-of-function and gain-of-function analyses on various Polycomb group (PcG) proteins. Absence of Bmi-1is preferentially linked with a profound defect in HSC self-renewal while forced expression of Bmi-1 but not other PcG genes led to a striking ex vivo expansion HSCs. We also demonstrated that Bmi-1 plays a role in the self-renewal of spermatogonial stem cells. These findings uncover novel aspects of stem cell regulation exerted through epigenetic modifications by the PcG proteins in hematopoietic as well as sperm stem cell system.
Sall1 is a mammalian homolog of the Drosophila region-specific homeotic gene spalt (sal). We found that mice deficient in Sall1 die in the perinatal period and that kidney agenesis or severe dysgenesis are present. Sall1 is essential for ureteric bud invasion, the initial key step for metanephros development. Using Sall1-GFP knockin mice, we also set up an in vitro culture system, in which a single renal progenitor in the metanephric mesenchyme forms colonies consisting of several types of epithelial cells. Thus our colony-forming assay, which identifies multipotent progenitors in the embryonic mouse kidney, can be used for determining mechanisms of renal progenitor differentiation.

10. Key Words