| Co-Investigator(Kenkyū-buntansha) |
HONDA Barry M Department of Biological Sciences, Simon Fraser University Associate Professor, 生物科学部, 準教授
BROCK Hugh W Department of Zoology, University of British Colunmbia Professor, 動物学部, 教授
HIGASINAKAGAWA Toru Department of Biology, School of Education, Waseda University Professor, 教育学部, 教授 (70131935)
TOMOTSUNE Daihachiro Research Institute for Microbial Diseases Research Associate, 微生物病研究所, 助手 (80283802)
TAKIHARA Yoshihiro Research Institute for Microbial Diseases Associate Professor, 微生物病研究所, 助教授 (60226967)
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| Research Abstract |
l) One of our major areas of interest has been to identify which Polycomb group (PcG) proteins interact, and to determine the interaction domains, both in flies and mammals. We have shown that three fly PcG proteins interact. Psc (Posterior sex combs) interacts with ph (polyhomeotic) and Pc (Polycomb), but ph and Pc do not interact. The same is true for their mouse homologues. RAE28 (ph), BMI1 (Psc), and M33 (Pc) interact homotypically. Both RAE28 and M33 interact with BMI1 , but not with each other. In addition, ph interacts with Scm (Sex comb on midleg) via a conserved domain found in many proteins. The mouse homologues of ph and Scm (RAE28 and mScm) also interact directly. Dr.Brock has further analyzed the conserved domain in more diverged proteins.
2) We found that the three mouse PcG genes have overlapping but not identical expression patterns during embryogenesis and in adult tissues. These gene products coimmunoprecipitate from embryonic nuclear extracts. Gel filtration analysis
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of embryonic extracts indicate that these proteins exist in multiple forms as large, multimeric complexes. The heterogeneity of coimmunoprecipitates appears to be cell type-specific, as M33 and RAE28 coimmunoprecipitate and copurify as members of large complexes from F9 cells, which express BMI1 at very low levels. These studies indicate that murine PcG proteins are developmentally regulated, and function as multiple, heterogeneous complexes.
3) To study the role of the rae28 gene in mouse development, we generated rae28-deficient mice by gene targeting in embryryonic stem cells. The anterior boundaries of Hoxa-3, a-4, a-5, b-3, b-4 and d-4 expression were shifted in the rostral direction in the paraxial mesoderms of the rae28^<-/-> homozygous embryos, and those of Hoxb-3 and b-4 expression were also similarly altered in the rhombomeres and/or pharyngeal arches. These altered Hox codes were presumed to be correlated with the posterior skeletal transformations and neural crest defects observed in the rae28^<-/-> homozygous mice. These results indicate that the rae28 gene is involved in the regulation of Hox gene expression and segment specification during paraxial mesoderm and neural crest development.
4) We are determining if rae28 gene can rescue the corresonding fly mutations (in progress). Less
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