On or Off? Using Protein Chimeras to Study Muscle Diversification
Disciplines
Developmental Biology | Molecular Genetics
Abstract (300 words maximum)
Diverse, complex tissues fascinatingly arise from a single fertilized egg during development. Mechanistically, proteins known as transcription factors (TFs) orchestrate the developmental program. The DNA-binding domain (DBD) of a TF binds specific DNA sequences, while the transactivation domain (TAD) recruits regulatory molecules to activate, or inactivate, nearby genes. How the limited number of TFs enables the great variety of observed tissues remains unanswered. Our study, therefore, asked how diversity is controlled in muscle tissue. In the embryo, all muscles are alike, but adult muscles differentiate into different types with unique properties and functions. We used the fruit fly, Drosophila, as a model system to study the regulation of the muscle gene Act57B. In fly embryos, Act57B is active in all muscles, but in adult flies, it becomes inactivated in many specialized muscles like flight muscles. MEF2 is a TF that activates Act57B in embryonic muscles. Interestingly, MEF2 is continuously present in all muscles, including flight muscles, where Act57B is inactivated. We hypothesized that during development, MEF2 somehow transforms from a positive regulator that activates Act57B to a negative regulator that represses Act57B. We used molecular cloning to replace the TAD of MEF2 with the TAD from another TF, Gal4. Using genetic reporter assays, we show that the new chimeric protein (Mef2::Gal4) can activate Act57B in cell culture. However, in flies, Mef2::Gal4 could not prevent repression of Act57B in flight muscles. Our results confirm that MEF2 is involved in the diversification of muscle tissue, but the mechanism of this action remains unknown.
Academic department under which the project should be listed
CSM - Molecular and Cellular Biology
Primary Investigator (PI) Name
Anton Bryantsev
On or Off? Using Protein Chimeras to Study Muscle Diversification
Diverse, complex tissues fascinatingly arise from a single fertilized egg during development. Mechanistically, proteins known as transcription factors (TFs) orchestrate the developmental program. The DNA-binding domain (DBD) of a TF binds specific DNA sequences, while the transactivation domain (TAD) recruits regulatory molecules to activate, or inactivate, nearby genes. How the limited number of TFs enables the great variety of observed tissues remains unanswered. Our study, therefore, asked how diversity is controlled in muscle tissue. In the embryo, all muscles are alike, but adult muscles differentiate into different types with unique properties and functions. We used the fruit fly, Drosophila, as a model system to study the regulation of the muscle gene Act57B. In fly embryos, Act57B is active in all muscles, but in adult flies, it becomes inactivated in many specialized muscles like flight muscles. MEF2 is a TF that activates Act57B in embryonic muscles. Interestingly, MEF2 is continuously present in all muscles, including flight muscles, where Act57B is inactivated. We hypothesized that during development, MEF2 somehow transforms from a positive regulator that activates Act57B to a negative regulator that represses Act57B. We used molecular cloning to replace the TAD of MEF2 with the TAD from another TF, Gal4. Using genetic reporter assays, we show that the new chimeric protein (Mef2::Gal4) can activate Act57B in cell culture. However, in flies, Mef2::Gal4 could not prevent repression of Act57B in flight muscles. Our results confirm that MEF2 is involved in the diversification of muscle tissue, but the mechanism of this action remains unknown.