In vivo micro-dissection and live embryo imaging by two-photon microscopy to study Drosophila melanogaster early developement

Animal embryo development exhibits a complex choreography of cell movements highly regulated both in time and space. This sequence of morphogenetic movements is initiated at gastrulation and is tightly controlled by a cascade of developmental gene expression. We have recently reported that developmental gene expression can in turn be mechanically regulated by morphogenetic movements during Drosophila melanogaster early development^[1]. In order to study this phenomenon of mechanically induced gene expression, it is necessary to develop new techniques of in vivo investigation. We show that the combination of femtosecond pulse intratissue surgery and two-photon-excitation fluorescence (2PEF) microscopy is a powerful tool for (i) disrupting natural morphogenetic movements and (ii) imaging native and disrupted morphogenetic movements during Drosophila development, (i) First, non-linear-absorption-mediated photo-disruption makes it possible to perform controlled intra-vital micro-dissections resulting in the modulation of morphogenetic movements and subsequent mechano-sensitive gene expression, (ii) Second, in vivo 2PEF microscopy of transgenic GFP systems appears to be an excellent technique for long-term in vivo imaging of the complex morphogenetic movements involved in normal or perturbed Drosophila gastrulation. Together, these two techniques provide a powerful novel approach to study embryo development.