Polyglutamine Aggregates Are Present in Committed Crypt Cells but Absent in Stem Cells in the Small Intestine of SCA3 Patients

<p>(A) Schematic representation of an intestinal crypt for visualisation of the different cell types present in this tissue. Light micrographs of a 4-μm (B) and 1-μm (C) section of a crypt from an SCA3 patient showing positive staining for anti-Musashi antibody. Note that stem cells are localised in between and on both sides of the morphologically recognizable Paneth cells residing at the base of the crypt. (D) A light micrograph of a crypt of a SCA3 patient showing positive staining for the anti-polyglutamine antibody IC2 in some epithelial cells (arrowheads). The asterisks (marked E–J) show representative positions of cells analyzed by subsequent electron microscopy. (E–J) show digitally modified, pseudo-coloured images of electron micrographs indicating the polyglutamine staining in blue. Differentiated epithelial cells (E), transit epithelial cells (F and I), and Paneth cells (J) contain polyglutamine aggregates (arrowheads). Stem cells (G) are negative for polyglutamine aggregates but occasionally contain micro-aggregates (H). Note that also some electron dense material is stained blue by this digital processing. In (G and H), contours are provided in black dashed lines to indicate the stem cells. Bars: D, 20 μm; E and H, 2 μm; F, 1 μm; G, I and J, 5 μm. (K) Quantification of cells with aggregates in the crypts of two SCA3 patients. As double labelling for aggregates and stem cells failed, only the stem cells that were adjacent to the Paneth cells were counted, because these could be easily identified on this basis.