In order to study the interplay between cell deformations and gene expression during Drosophila embryo development, we have designed experimental approaches for micromanipulating tissue compression state in vivo with physiologically relevant forces.

First, we developed intravital microsurgery based on femtosecond pulse-induced ablation. Targeted disruption of specific cells modify the embryo structural integrity, and result in the long distance modulation of particular morphogenetic movements.

      

Second, we used magnetic manipulation of a microinjected ferrofluid, which enabled us to restore tissue compression in ablated embryos. We combined these approaches with multiphoton microscopy (2PEF/THG). It is then possible to control tissue compression state in vivo, and to obtain a quantitative description of tissue deformations during subsequent embryo development.

We used this strategy to analyze the correlations between tissue deformations and mechano-sensitive gene expression. This led us to the demonstration that the developmental gene Twist is over-expressed in response to the forces developped during embryo morphogenesis in midgut precursor cells through a beta-catenin-dependent process, and that this mechanism is necessary for proper midgut formation.
These findings may be relevant in other contexts such as tumor progression.

RELATED PUBLICATIONS

"Tissue deformation modulates Twist expression to determine anterior midgut differentiation in Drosophila embryos"
N. Desprat, W. Supatto, P.-A. Pouille, E. Beaurepaire & E. Farge
Dev. Cell 15(3) 470-477 (2008). PDF.
"In vivo modulation of morphogenetic movements in Drosophila embryos with femtosecond laser pulses"
W. Supatto, D. Débarre, B. Moulia, E. Brouzés, J.-L. Martin, E. Farge & E. Beaurepaire
PNAS 102(2), 1047-1052 (2005). PDF.
"Velocimetric third-harmonic generation microscopy: micrometer-scale quantification of morphogenetic movements in unstained embryos"
D. Débarre, W. Supatto, E. Farge, B. Moulia, M.-C. Schanne-Klein & E. Beaurepaire
Opt. Lett. 29(24), 2881-2883 (2004). PDF.
"Femtosecond pulse-induced microprocessing of live Drosophila embryos"
W. Supatto, D. Débarre, E. Farge & E. Beaurepaire
Med. Laser Appl. 20(3), 207-216 (2005). PDF.