Abstract
Smad4 is a key signal transducer of the transforming growth factor-β (TGF-β) superfamily of growth factors that are critical regulators of embryonic patterning and adult tissue homeostasis. The biological activity of the TGF-β signaling is tightly controlled at multiple levels, including the abundance of SMAD4 proteins. We previously recovered a novel allele of Smad4 in a gene-based screen in N-ethyl-N-nitrosourea (ENU)-mutagenized mouse embryonic stem cells. The mutation resulted in an unstable truncated protein that is degraded through proteasomal pathways. In the heterozygous state, this allele acts in a dominant negative fashion to reduce the wild-type protein level as well as signaling output. Biochemical characterization indicated that the truncated protein is able to form a complex with the wild-type protein, thus targeting it for proteasomal degradation as well. Phenotypic analyses of the heterozygous animals provided insight into the threshold requirement of Smad4-dependent signaling in vivo.
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Acknowledgments
The authors thank C. Deng for providing Smad4 targeted mice and Chamberlain S. for helpful comments on the manuscript. This work was supported by an NIH postdoctoral fellowship to YC and an NIH grant to TM.
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Chen, Y., Yee, D. & Magnuson, T. A novel mouse Smad4 mutation reduces protein stability and wild-type protein levels. Mamm Genome 17, 211–219 (2006). https://doi.org/10.1007/s00335-005-0074-3
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DOI: https://doi.org/10.1007/s00335-005-0074-3