Relationship between MMP immunostaining and gelatinolytic activity at the midline epithelial seam of opposing palatal shelves during their fusion.

Frontal cryosections of E15.5 wild type mouse heads were subjected to DQ-gelatin zymography (A, D), followed by immunofluorescence labeling for MMP-2 (B) or MT1-MMP (E) on the same section. Merged images are shown in C and F. At the midline, some colocalization with gelatinolytic activity is evident only for MMP-2 (arrows). MT1-MMP shows weak colocalization with activity at the midline epithelium (arrows) and is more strongly colocalized with gelatinolysis in fibrillar structures adjacent to remnants of the midline epithelium (arrowheads). For more details, see Results. p, palatal shelf. Bar, 50 μm.