MMPs are required for the formation of filopodia and lamellopodia at the leading edge.

<p>Live embryos expressing <i>tup-GFP</i> (to visualise CB nuclei) and <i>UAS-Moesin-mCherry</i> under the control of <i>mef2-GAL4</i> driver are visualised. Thin cytoplasmic protrusions were identified as filopodia, whereas sheet-like extensions were categorised as lamellopodia. (A-A”) In wildtype embryos, CBs extend finger-like filopodia (arrow) and sheet-like lamellopodia (arrowhead) towards their contralateral partner cells. CBs make contact at the dorsal midline (arrowhead). (B-B”) In <i>mmp1</i> mutants, filopodial and lamellopodial activity at the leading edge is reduced (arrow) and CBs form short outgrowths towards their contralateral partners (arrowhead). (C-D”) In <i>mmp2</i> and <i>mmp1</i>,<i>mmp2</i> mutants delayed migration is observed (asterisk). CBs extend reduced numbers of filopodia and lamellopodia (C’,D’ arrow). CBs appear rounded without apical extensions towards the midline (C”,D” arrowheads). (E-E”) Expression of a <i>mmp2</i> transgene in the CBs of <i>mmp2</i> mutants restores formation of filopodia, lamellopodia (arrows) and apical outgrowths (arrowhead). Scale—25 μm in A-E and 10 μm in A’-E”.