| Research Abstract |
In order to investigate the fundamental molecular mechanisms of stem cell systems, two kinds of stem cells were analyzed. One is totipotent mouse embryonic stem cells (ES cells) and the other is germ line stem cells, namely, primordial germ cells (PGC).
Myb family genes are known to posess essential roles in cell differentiation. We utilized a conditinal dominant negative Myb (MERT), which represses the function of all members of Myb (c-, A- and B-Myb). ES cells express B-Myb almost exclusively among Myb family members. Thus, the activation of MERT brings about the suppression of B-Myb function. Unfortunately, the suppression of B-Myb function does not alter differentiation status of ES cells. In stead, cell cycle and cell adhesion are affected. The alteration of cell cycle is reasonable from previous reports and expression pattern of B-Myb. However, the alteration of cell adhesion is a new finding. Precise examination revealed that the change of surface expression of cadherin and integrin was initiated by the inhibition of B-Myb. Considering that the transcription level of these two adhesion molecules was not changed, it is probable that some post-transcriptional modification was caused by the inhibition of B-Myb. Together with the data of B-Myb knock our mice, B-Myb is essential for cell adhesion at the early embryogenesis.
TNAP (tissue non-specific alkaline phosphatase)-EGFP knock in mouse was produced and used for isolating PGCs from mouse developing embryos. Gene expression in ES cells and PGCs was analyzed by SAGE analysis. About 10,000 expression tags were sequenced from both sources. A couple of the family genes were preferentially expressed in either ES cells or PGCs. And one novel gene expressed in ES cells and PGCs was cloned.
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