Fig. 1. Ablation of oligodendrocytes alters cerebellum development. (A-D) HSV1-TK expression is restricted to MBP-positive oligodendrocytes (arrowheads). Cerebellar sections from a 2-day-old (P2) untreated MBP-TK mouse were double stained with anti-HSV1-TK (red) and MBP (green) antibodies. Nuclei were stained with DAPI (blue). (D) Merging of the different stains shows nuclear localization of TK in MBP-positive cells. Sections were analyzed by confocal microscopy. (E,F) Immunofluorescence analysis of TK-positive oligodendrocytes in cerebellar folia IX of P6 untreated (E) versus treated (F) MBP-TK mice, using the anti-HSV1-TK antibody. (G-J) Cresyl Violet staining of paraffin wax-embedded cerebella sagittal sections from wild-type (G,I) and MBP-TK (H,J) mice treated from day 1 to 20. The cerebellum of the treated wild-type animal presents a normal architecture both at high (G) and low (I) magnification. The cerebellum of the treated MBP-TK mice is smaller with an abnormal foliation (J; star) and a highly disorganized cortex (H). The fissura intercruralis in both wild-type and MBP-TK mice is indicated by a star (I,J). Arrows (G,H) show Purkinje cell bodies. ML, molecular layer; IGL, internal granular layer; WM, white matter tract. (K,L) Cerebellar sagittal sections immunostained with an anti-MBP antibody from 3-week-old wild-type (K) and MBP-TK (L) mice treated from day 1 to 21. Note rare MBP-positive fibers in treated MBP-TK mice (arrow; L). Scale bars: 5 µm (A-D), 80µm (E-F), 30 µm (G-H), 300 µm (I-J), 100 µm (K-L).