Pdlim7 regulates nuclear/cytoplasmic localization and activity of Tbx5 during cardiac development
Pdlim7 regulates nuclear/cytoplasmic localization and activity of Tbx5 during cardiac development Troy Camarata The T-box transcription factor, Tbx5, is involved in heart development and congenital disease. For example mutations in human TBX5 lead to Holt-Oram syndrome, a disease characterized by a range of heart and arm malformations. Tbx5 gene activity has been perturbed in several animal models including the chicken, mouse, and zebrafish. In zebrafish, the tbx5 heartstrings (hst) mutation
... s (hst) mutation results in embryos that fail to develop pectoral fins (forelimbs) and form a non-looped, string-like heart. Despite the importance of Tbx5 in heart formation, little is known about its function and regulation. To gain insight into Tbx5 regulation, the Simon laboratory performed a yeast two-hybrid screen to identify interacting proteins. One candidate isolated from the screen was Pdlim7, a member of the PDZ-LIM protein family. I hypothesized that the binding of Tbx5 to Pdlim7 modifies its transcriptional activity and explored the consequences of Tbx5/Pdlim7 complex formation in vitro employing appropriate cultured cells and in vivo using the zebrafish embryo. Evidence from others in the laboratory using in vitro binding studies and in vivo protein localization in the chicken limb and heart suggested an interaction between Tbx5 and Pdlim7. However, what is the mechanistic action of the Tbx5/Pdlim7 complex on a cellular level? Using co-immunoprecipitations and confocal imaging I demonstrated that Tbx5 and Pdlim7 bind in the cell. In the presence of Pdlim7, employing FRAP, I was able to show that Tbx5 shuttles dynamically between the nucleus and cytoplasm and, in a complex with Pdlim7, localizes to the actin cytoskeleton. To test whether the relocalization from nuclear to cytoplasmic sites Table of Contents Abstract .