Figure 7

Endogenous CAC and CAG rich mRNAs are localized to distal processes in mammalian neurons. In situ hybridization was used to reveal the subcellular distribution of each mRNA in rat hippocampal neurons that had been cultured for 8 days after plating. Stx5 was used as a negative control for localization since it has no repeats and resides exclusively in the cell body. CamKIIα was used as a positive control for localization since it is well known to localize well to distal processes. White arrows show labelling in distal processes. All images were collected at identical laser settings using confocal microscopy and all images were processed together as a montage image to enhance contrast. In addition all cells came from the same experiment and each cell has multiple processes in the focal plane, but often a single process is preferentially labelled. The identity of processes as either axons or dendrites is not yet known. Specific mRNAs were detected in distal processes with both CAC-rich mRNAs (Tubβ4 and Syn1B2) and both CAG-rich mRNAs (Syn1A and Sec61α) that were identified with 3'-UTR SIRF. The cell bodies in these images are approximately 15 μm in diameter.