Melanie Gettings

Melanie Gettings · Copy Editor

Epithelium folding is a basic morphogenetic event that is essential in transforming simple two-dimensional epithelial sheets into three-dimensional structures in both vertebrates and invertebrates. Folding has been shown to rely on apical constriction. The resulting cell-shape changes depend either on adherens junction basal shift or on a redistrib...

What triggers a differentiated cell to naturally change its cell fate? Cell reprogramming is a rare and intriguing phenomenon, from a developmental point of view. It has been mostly involved in boundary sharpening during development, tissue regeneration and cancer. Developmental models of the understanding of pathology-related cell reprogramming ar...

In Drosophila melanogaster, dorsal closure is a model of tissue morphogenesis leading to the dorsal migration and sealing of the embryonic ectoderm. The activation of the JNK signal transduction pathway, specifically in the leading edge cells, is essential to this process. In a genome-wide microarray screen, we identified new JNK target genes durin...

JNK activity controls mixer cell formation and En expression. (A) Expression of endogenous Ptc and En proteins in a hepr75/hep1 mutant embryo. Note that in these mutant embryos the mixer cell expresses Ptc but not En in contrast to wild type embryos. Ptc, green; DAPI, turquoise; En, red. Scale bars: 5 µm. (B) Embryos overexpressing the JNK phosphat...

JNK down-regulation in the anterior compartment inhibits cell intercalation. Confocal still images from Video S4 showing an embryo expressing BskDN in the anterior compartment. Genotype: ptc-gal4, UAS-bskDN, UAS-RFP; βcatenin-GFP. βCatenin-GFP, white; RFP, green. Colour code as in Figure 1B. Scale bars: 10 µm. (2.31 MB TIF)

JNK overactivation induces ectopic mixer cells and intercalation. Confocal time-lapse imaging of an embryo expressing the JNKK Hep in the anterior compartment from Video S5. Genotype: ptc-gal4, UAS-hep; βcatenin-GFP. βCatenin-GFP, green. Colour code as in Figure 4A. Scale bars: 10 µm. (2.41 MB TIF)

Timing and standard deviations of closure and cell intercalation described in Figure 1E . (0.04 MB DOC)

Dorsal closure of a wild type embryo. Confocal time-lapse images are taken from an embryo expressing ubiquitous αCatenin-GFP (green) and h-Actin-CFP (red) in the posterior compartment. Genotype: βcatenin-GFP; en-gal4, UAS-h-actin-CFP. (6.40 MB MOV)

Expression of cellular markers in the mixer cells. (A, B) Pattern of Ena (A), Ptc (B), puc-lacZ, and En expression at three different stages of cell mixing: before anterior-to-posterior mixer cell shifting (top panels); after the onset of mixer cell shifting and cell intercalation (middle panels); end of cell mixing and intercalation (bottom panels...

Time-course of Engrailed expression in the mixer cells. Examples of En stainings used for the quantification of the relative amounts of En in the mixer cells compared to neighbouring bona fide En cells. The bottom panel shows a scheme of the intercalation stages (mixer cell, yellow; PI, red; AI, green; posterior, orange; anterior, light green).Ena,...

Expression pattern of the en-gal4 driver. Still images of an A4 segment of a βcatenin-GFP,en-gal4 > UAS-lamin-GFP live embryo, from early stage 15 to stage 16. (A) Normal image. (B) False colouring (red) of the dorsal row of En cells. (C) Increasing the brightness allows the visualization of lamin-GFP weak expression in the mixer cells (red arrows)...

Dynamics of cell mixing and intercalations at the segment boundaries. Summary cartoon showing the spatial and temporal dynamics of mixer cell shifting and cell intercalations at the segment boundaries. (2.73 MB MOV)

Absence of intercalation in an embryo defective for JNK signalling in the anterior compartment. Confocal time-lapse imaging of an embryo expressing a dominant negative form of Bsk in the anterior compartment. Genotype: ptc-gal4, UAS-bskDN; βcatenin-GFP. βcatenin-GFP, green. Colour code as in Figure 4A. Scale bars: 10 µm. (0.82 MB MOV)

Excessive intercalations in an embryo overexpressing JNKK in the anterior compartment. Confocal time-lapse imaging of an embryo overexpressing the JNKK Hep in the anterior compartment. Genotype: ptc-gal4, UAS-hep, UAS-RFP; βcatenin-GFP. βCatenin-GFP, white; RFP, green. Colour code as in Figure 4A. Scale bars: 10 µm. (0.56 MB MOV)

High magnification of segment boundary remodelling in a wild type embryo. High magnification of the A3–A4 segment boundary during dorsal closure showing mixer cell shifting and cell intercalations. Confocal time-lapse images are taken from an embryo expressing ubiquitous βCatenin-GFP (green) and Actin-CFP (red) in the posterior compartment. Genotyp...

Absence of intercalation in an embryo overexpressing Wg in the anterior compartment. Confocal time-lapse imaging of an embryo overexpressing Wg in the anterior compartment. Putative most anterior cells of segments A2 to A6 are coloured in green to show that no intercalation occurs in the entire bracketed region. Genotype: ptc-gal4, UAS-wg; βcatenin...

Author Summary Multicellular organisms are assembled from different cell types, each following a particular fate depending on their history and location. During development, cells are organized into compartments, which are essential for the correct formation of organs. Within the compartments, cells follow two general rules: (i) cells that have acq...