Preparation of Precisely Oriented Cryosections of Undistorted Drosophila Wing Imaginal Discs for High Resolution Confocal Imaging.

The combination of immunofluorescence and laser scanning confocal microscopy (LSM) is essential to high-resolution detection of molecular distribution in biological specimens. A frequent limitation is the need to image deep inside a tissue or in a specific plane, which may be inaccessible due to tissue size or shape. Recreating high-resolution 3D images is not possible because the point-spread function of light reduces the resolution in the Z-axis about 3-fold, compared to XY, and light scattering obscures signal deep in the tissue. However, the XY plane of interest can be chosen if embedded samples are precisely oriented and sectioned prior to imaging (Figure 1). Here we describe the preparation of frozen tissue sections of the Drosophila wing imaginal disc, which allows us to obtain high-resolution images throughout the depth of this folded epithelium.