Fig. 2. Embryonic expression profiles of Mmp1 and Mmp2. (A-E,G,H) Stage 15 wild-type embryos stained for indicated markers. (F) Stage 15 gcm^P1 homozygous mutant embryo stained for Mmp2 RNA and labeled with anti-Repo. (A) Mmp1 is expressed in PNS neurons in the chordotonal organs and (B) in two cells in the ventral longitudinal muscle field (arrows). (C) Expression of Mmp2 RNA indicates that Mmp2 is expressed in a subset of CNS neurons and glia (circled in red). (D) Mmp2 RNA (green) colocalizes with anti-Wrapper (red) in midline glia. (E) Nuclear anti-Repo (brown) and cytoplasmic Mmp2 RNA (purple) in a subset of exit glia (arrows). (F) In gcm^P1 embryos, which lack most glia, Mmp2 RNA is no longer expressed at the lateral edge of the CNS where the exit glia are located (arrows). (G) Anti-Islet (brown) colocalizes with Mmp2 RNA (purple) in approximately three neurons per hemisegment (arrows). The location of these neurons is consistent with an interneuron identity. (H) Anti-Hb9 (brown) does not colocalize with Mmp2 RNA (purple). Insets in G and H show high-magnification views of Mmp2 expression. Dotted white line marks the CNS boundary. Anterior is up in all panels. Dorsal is right in A,B,E,F. Scale bars: 10 µm in A,B,E,F; 20 µm in C,D,G,H.