Scientific Report 2003-2004 - Cleveland Clinic Lerner Research ...

Our laboratory is interested in understandingthe mechanisms that controlthe balance between proliferation anddifferentiation during development. Our focusis on the ski oncogene family, whose twomembers, ski and sno, encode transcriptionalregulators that can affect both oncogenictransformation andcellular differentiation.We use gene targetingand transgenictechniques to study thedevelopmentalprocesses that requirethe function of ski andsno in mice, as modelsfor human development.Both ski and snohave been shown tofunction as coactivatorsor corepressors,modulatingtranscription byinteracting with severaldifferent transcriptionfactor complexes.Those interacting withski include members ofthe Nuclear Factor I(NFI) family, theretinoic acid receptor,and the nuclearhormone co-regulators NCoR and skip/NCoA62, and members of the Smad genefamily. Their ability to interact with multipletranscription factors, coupled with theirubiquitous expression, suggests that ski and snoare involved in regulating the expression of alarge, diverse group of genes. Therefore, wehave undertaken a genetic approach, introducingmutations into ski and sno genes to uncoverthe developmental pathways that require theirfunctions.A long-standing area of interest in thelaboratory has been the role of the ski genefamily in skeletal muscle differentiation. Bothski and sno have the surprising property ofinducing, simultaneously, both myogenicdetermination and oncogenic transformation.In vivo, overexpression of ski in skeletalmuscles of transgenic mice induces hypertrophyof specific fiber types. In our ski-deficientmice, skeletal muscle development is defective,as shown by a dramatic reduction in skeletalmuscle mass and fiber organization. We arecurrently using these mutant mice to identifyspecific stages during skeletal muscle differentiationthat require ski expression.The Department of Cancer BiologyProto-Oncogenes ski, sno:Global Regulators of Differentiationand DevelopmentA new focus for our laboratory is the studyof craniofacial defects in ski-deficient mice. Wehave found that ski -/- mice show either a neuraltube defect or median facial clefting and that thepenetrance of these two phenotypes is completelydependent on genetic background. Theseresults suggest that mutations in ski may berelevant to humanfacial clefting, whichis one of the mostcommon birthdefects. These dataled us to correctlypredict the involvementof ski in ahuman geneticsyndrome, monsomy1p36, in which theobserved featuresinclude not only facialclefting, but alsoother phenotypes incommon with ski-nullmice, such as musclehypotonia, openfontanels, and adepressed nasalbridge. Our continuingefforts involvemapping of modifierClemencia Colmenares, Ph.D.genes, and searchingfor mutations in skiamong other familieswith facial clefting defects.Because sno has the same activities as skiwhen over-expressed in vitro, and both genes areexpressed ubiquitously, it seemed likely that theywould have overlapping activities. Our analysesof double-mutant mice lacking both ski and snosuggest that, although there is some functionalredundancy, there are also gene-specific functionsthat lead to distinct phenotypes.THE COLMENARESLABORATORYTECHNOLOGISTBinh To, B.S.Yuanhua LiuGRADUATE STUDENTYishi Chen, M.S.COLLABORATORSHeidi Heilstedt, M.D. 1Shunsuke Ishii, Ph.D. 2Sonia Pearson-White, Ph.D. 3Lisa Shaffer, M.D. 1Edward Stavnezer, Ph.D. 41Dept. of Molecular and HumanGenetics, Baylor Coll. ofMed., Houston, TX2RIKEN Tsukuba Life ScienceCtr., Tsukuba, Japan3Univ. of Virginia, Charlottesville4Case Western Reserve Univ.,Cleveland, OHBerk, M., Desai, S. Y., Heyman, H. C., and C. Colmenares (1997) Mice lacking theski proto-oncogene have defects in neurulation, craniofacial, patterning, and skeletalmuscle development. Genes Dev. 11:2029-2039.Shinagawa, T., Nomura, T., Colmenares, C., Ohira, M., Nakagawara, A., and S. Ishii(2001) Increased susceptibility to tumorigenesis of ski-deficient heterozygous mice.Oncogene 20:8100-8108.Colmenares, C., Heilstedt, H.A., Shaffer, L.G., Schwartz, S., Berk, M., Murray, J.C.,and E. Stavnezer (2002) Loss of the SKI proto-oncogene in individuals affected with1p36 deletion syndrome is predicted by strain-dependent defects in Ski-/- mice. Nat.Genet. 30:106-109.Dai, P., Shinagawa, T., Nomura, T., Harada, J., Kaul, S.C., Wadhwa, R., Khan, M.M.,Akimaru, H., Sasaki, H., Colmenares, C., and S. Ishii (2002) Ski is involved intranscriptional regulation by the repressor and full-length forms of Gli3. Genes Dev.16:2843-2848.51