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(1) Presentation(s)

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Mar. 04/11/2014 10:30 Andromede, Bâtiment 11, Etage 3

Séminaire
FERRARO Teresa (ENS Paris - Institut Curie)
Dynamics of transcription during early Drosophila patterning

(Physique Statistique)


Sommaire:

The early Drosophila embryo is an ideal model to understand the transcriptional regulation of well-defined patterns of gene expression in a developing organism. The first step in the spatial organization of an organism consists of the establishment of the Anterior-Posterior polarity axis. In the fruit fly, the maternal morphogen Bicoid (Bcd) forms a spatial gradient with high concentration at the anterior pole that exponentially decreases toward the posterior. Bcd activates the target gene hunchback (hb) which shows an homogeneous and sharp a domain of expression in the anterior half of the embryo. Recently my biology collaborators developed a technique to observe live transcription in transgenic flies, by genetically modifying the hb gene with an MS2-MCP fluorescent tag, opening the possibility of studying the dynamics of gene pattern formation. We used the MS2-MCP system to visualize nascent transcripts expressed from the typical hb promoter under the control of the morphogen Bcd. We developed a segmentation and tracking algorithm to analyze the data. We find that the transgene used shows an hb expression as homogeneous as the non-modified hb gene in the anterior half of the embryo, but unlike non-modified hb it is also shows activity in the posterior, though more heterogeneously and more transiently than in the anterior. We propose that the establishment of the hb pattern relies on Bcd-dependent lengthening of transcriptional activity periods in the anterior and may require two distinct repression mechanisms in the posterior. Additionally, I discuss theoretical models that aim at understanding the details of spatial and temporal regulation in this system.


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