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Home page > Research Groups > Mounia LAGHA - Transcription Regulation During Developement

Mounia LAGHA - Transcription Regulation During Developement

Research Goals

Gene expression is precisely controlled in time and space during the development of metazoan embryos. While numerous studies have established how the spatial information is achieved and integrated by gene regulatory regions known as enhancers, less is known concerning "timing", i.e. the temporal coordination of gene expression across a field of cells.

Our overall goal is to understand the developmental consequences of subtly altering the timing of gene activation, using Drosophila melanogaster as a model system.

We mainly study early Drosophila development : the first 4 hours of embryogenesis.

The approach is highly integrative with techniques ranging from classical genetics and molecular biology to whole-genome profiling and state of the art live imaging microscopy.


Mounia Lagha Lab

www.laghalab.com

1-Mechanisms of transcriptional timing

Promoter elements and temporal coordination


Our recent promoter swapping experiments followed by Pol II-ChIP or permanganate footprinting assay suggest that minimal promoter sequences (-50, +50bp from the TSS) are sufficient to create de novo pausing in vivo (Lagha et al., 2013). However, within this 100 bp of DNA sequence, the relative importance of their constituting elements is poorly understood. We are therefore investigating the role of various core promoter elements (e.g., TATA and GAGA) in transcriptional timing. Live imaging and quantitative analysis on reporter transgenes will be used.

You can see a typical movie in the ’’video’’ section.

Snapshots from a MS2 movie on a living Drosophila early embryo.

Mitotic memory

Under certain conditions, we are able to reveal the existence of a transcriptional memory. After mitosis, the first nuclei that exhibit transcription are those deriving from active mother nuclei in the preceeding cell cycle.

We are currently characterizing this very interesting mitotic bookmarking phenomenon.

2-Temporal coordination and the Dpp pathway

Dpp/BMP is a conserved morphogen, which is essential for the patterning of a variety of tissues in many different metazoan systems. In Drosophila, Dpp/BMP signaling is required for patterning the dorsal region of the early embryo, where peaks of Dpp determine the dorsal ectoderm and amnioserosa cell fates (reviewed in O’Connor et al., 2006).

Most previous efforts to analyze Dpp signaling have been restricted to gene knock-out approaches. Although these have led to the very good understanding of how Dpp/BMP morphogen is integrated in a sophisticated network, very little is known concerning the dynamics of this complex network.

What are the physiological consequences of altering the timing of Dpp/BMP pathway?

Is temporal coordination in gene transcription required for appropriate cell fate specification in the dorsal ectoderm?

We are currently investigating these questions in genetic backgrounds where the timing of Dpp signaling has been subtly altered.

Phospho-Mad (pMad) immuno-staining in a wild type cc14 embryo. pMad is a readout for Dpp signaling activity. Nuclei are stained with Dapi.

3-Temporal coordination and heart development

Heart specification constitutes an ideal system to examine the question of timing and priming during cell fate decisions.

The Drosophila embryonic heart consists of two major cell types which are very precisely organized. Each hemisegment of the mature posterior embryonic heart (stage 16) is composed of two types of cardioblasts and three types of pericardial cells (see Figure).

In this project, we plan to understand whether temporal coordination plays a role in generating the precise and reproducible pattern of different cell fates observed during cardiogenesis.

Drosophila embryonic heart.

Selected publications :

1-Lagha M, Bothma J, Esposito E, Samuel Ng, Stefanik L, Tsui C, Johnston J, Chen K, Gilmour D,Zeitlinger J and Levine M. Paused Pol II coordinates tissue morphogenesis in the Drosophila embryo. (2013) Cell; 153(5) 976-87.

2-Lagha M, Chang T, Mayeuf A, Montarras D, Rocancourt D, Kormish J, Zaret K, Buckingham M and Relaix F. Itm2a is a Pax3 target gene, expressed at sites of skeletal muscle formation in vivo. (2013) PlosOne;(5):e63143.

3-Lagha M, Bothma J and Levine M. Mechanisms of transcriptional precision in development. (2012) Trends in Genetics; (8)409-16

4-Relaix F, Demignon J, Laclef C, Pujol J, Santolini M, Niro C, Lagha M, Rocancourt D, Buckingham M,Maire P. Six homeoproteins directly activate myod expression in the gene regulatory networks that control early myogenesis. (2013) Plos Genetics; (4):e1003425.

5-Lagha M, Sato T, Regnault B, Cumano A, Zuniga A, Licht J, Relaix F and Buckingham M Transcriptome analyses based on genetic screens for Pax3 myogenic targets in the mouse embryo. (2010) Bio Med Central Genomics; 11:696.

6-Lagha M, Brunelli S, Messina G, Cumano A, Kume T, Relaix F and Buckingham M. Pax3:Foxc2 repression in the somite modulates muscular versus vascular cell fate choice in multipotent progenitors. (2009) Dev Cell; 17(6):892-9.

7-Lagha M, Sato T, Bajard L, Daubas P, Esner M, Montarras D, Relaix F, Buckingham M. Regulation of Skeletal Muscle Stem Cell Behavior by Pax3 and Pax7. (2008) Cold Spring Harb Symp Quant Biol; Vol.LXXIII, 73:307-15.

8-Lagha M, Kormish J, Rocancourt D, Manceau M, Epstein JA, Zaret KS, Relaix F and Buckingham M.Pax3 regulation of FGF signaling affects the progression of embryonic progenitor cells into the myogenic program, (2008) ,Genes Dev ; 22:1828-37.

9-Bajard L, Relaix F, Lagha M, Rocancourt D, Daubas P and Buckingham M. A novel genetic hierarchy functions during hypaxial myogenesis : Pax3 directly activates Myf5 in muscle progenitor cells in the limb. (2006), Genes Dev; 20 :2450-64.

10-Buckingham M, Bajard L, Daubas P, Esner M, Lagha M, Relaix F, Rocancourt D. Myogenic progenitor cells in the mouse embryo are marked by the expression of Pax3/7 genes that regulate their survival and myogenic potential. (2006) ,Anat Embryol (Berl) 211 :51-6.

11-Lagha M, Rocancourt D and Relaix F. Pax3/Pax7-dependent population of skeletal muscle progenitor cells. Médecine Sciences, (2005), 21: 801-3.


Institut de Génétique Moléculaire de Montpellier
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