The physical and dynamical properties of transcriptional microenvironments during embryonic development

• Applicant: Dr. Albert Tsai
• Subject Area: Developmental Biology ; Biophysics
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426035257

Master developmental transcription factors determine animal body plans through controlling the expression of many downstream target genes. Recent studies have shown that transcription of these genes occur from low affinity binding sites in microenvironments of high local transcription factor concentrations. We have shown in Drosophila melanogaster embryos with the master transcription factor Ultrabithorax (Ubx) that these nuclear microenvironments are highly dynamic. We propose to investigate their physical and dynamical properties inside living Drosophila embryos through the following aims. 1) To track how enhancers interact with microenvironments regardless of their transcriptional states, we plan to directly mark specific loci near Ubx regulated enhancers in Drosophila for imaging in both fixed and live embryos. 2) We have seen that Ubx and AbdA, two factors with indistinguishable consensus binding sequences, spatially segregate in the same nucleus. We aim to fluorescently tag AbdA and additional variants of Ubx with different interaction domains. A toolbox of tagged Ubx and AbdA will allow us to observe how these proteins dynamically sort into their respective microenvironments. 3) The chromatin, which is the backbone for microenvironment, also changes its conformation during development. We plan to generate fly lines with multiple tagged locations on the chromatin. This library will allow us to gauge the positioning and movement dynamics of the chromatin during development to provide a general context within which to place Ubx-driven enhancers. In sum, this proposal seeks to combine rigorous biophysical quantitation with the genetic toolbox of developmental biology to address how the physical organization of the nuclear space can specifically and precisely regulate transcription in both space and time.

• DFG Programme: Research Grants