C-rich transcripts of PO41 repeat in chicken small intestine cells. FISH with PO41pos (green, upper row) and PO41neg (red, bottom row) probes on small intestine cryosections. (a, a’) DNA/RNA hybridization revealed C-rich (green), but not G-rich (red) PO41 repeat transcripts in mucous membrane of chicken small intestine. (b, b’) DNA/DNA hybridization (positive control) revealed clusters of PO41 repeat in all cell nuclei. (c, c’) RNase A treatment before DNA/RNA hybridization (negative control) removed hybridization signals with PO41pos probe from the cell nuclei, but didn’t remove signals in cytoplasmic granules within the mucous membrane. Right-hand images demonstrate enlarged fragments of muscles layer (upper panels) and mucous membrane (bottom panels) of small intestine. Nuclei were counterstained with DAPI. Scale bar: 40 μm.