| Description: | [Institute Colloquium] Prof. Eric Wieschaus (Dept. of Molecular Biology, Princeton University) -- Inputs, Outputs and Cell Signaling during Early Development |
| Date: | Wednesday, Jan 15, 2020 |
| Time: | 4:30 p.m. - 5:30 p.m. |
| Venue: | Meghnad Saha Lecture Theatre |
| Details: | During embryonic development in all organism, cell fates are established by local differences in transcription. In Drosophila the region-specific activation of gap and pair-rule gene that establish anterior posterior pattern is controlled by three distinct and overlapping maternal gradients encoded by the bicoid, nanos and torso-like genes. These three gradients establish expression patterns with an accuracy that distinguishes single cells from their immediate anterior and posterior neighbors. To analyze the strategies used by the embryo to achieve accuracy, we have combined information theory approaches with high throughput molecular characterization of in vivo enhancer affinities. One part of our experiments uses a Bayesian-based system of “look-up” tables to measure the information content in concentration profiles. This analysis shows that precision is established by ten minutes into cycle 14 and persists until 40 minutes when pair-rule gene expression is well established. This transcriptional activation seem rapid and direct, with little evidence of systems-level stepwise interactions. Using ChIP seq from embryos expressing different concentrations of the major transcription factor involved (Bicoid), we compare the in vivo binding affinities of enhancers that activate expression at different points along the AP axis of the embryo. We find that enhancers expressed in the posterior of the embryo have high affinities and remain bound even at lowest concentration. We propose chromatin models for how the low levels of Bicoid protein in these regions might activate enhancers in a concentration dependent manner. |
| Calendar: | Seminar Calendar (entered by arnab.gupta) |