| Budget Amount *help |
¥3,960,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥360,000)
Fiscal Year 2007: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2006: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
Notch signaling has been shown to play an important role in a number of different cell fate decisions. Several loss-of-function studies have revealed that Notch signaling plays an essential role in the multiple developmental stages for hematopoiesis, namely, generation of the definitive hematopoiesis, commitment to T cell fate in the thymus, development from thymic CD4 CD8 double negative (DN) T cells to double positive T cells, and development of splenic marginal zone (MZ) B cells. Previously, we have identified a human Mastermind (Mam) family of proteins, consisting of three members (Mam-1, Mam-2, and Mam-3) and thus elucidated their biochemical mechanisms of action. All of the Mam proteins bind to and stabilize the DNA-binding complex of the intracellular domains of Notch and CSL proteins in the nucleus to activate transcription from target promoters. In this term of project, we have generated a line of Mam-1-deficient mice and found that Mam-1 deficiency abolishes the development of splenic MZB cells, a subset strictly dependent on Notcli2, a CSL protein and Delta 1 ligand. Mam-1 deficiency also causes a partially impaired development of early thymocyres, while not affecting the generation of definitive hematopoiesis, processes that are dependent on Notch1. We also demonstrate the transcriptional activation of a target promoter by constitutively active forms of Notch to decrease severalfold in primarily cultured Mam- 1-deficient cells. These results indicate that Mam-1 is thus required to some extent for Notch-dependent stages in lymphopoiesis, thus supporting the notion that Mam is an essential component of the canonical Notch pathway in mammals.
We also found that the non-canonical Notch target Hes3 promoter can be activated by a product of a gene (MAMLD1) that holds structural similarity with Mam and of which deletion causes hypospadia in humans.
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