Fig. 2. Analysis of the cerebellar phenotype of Rb and Rb/p107 compound mutant mice. Sagittal sections of wild-type (A-E) (n=3), Rb (F-J) (n=3) and Rb/p107 compound mutant (K-T) (p107^+/-; n=3, p107^-/-; n=4) cerebella at P20. NeuN immunostaining (A,F,K,P) reveals marked loss of granule cells in the Rb-deficient vermis (F), while additional loss of one or both p107 alleles results in impaired terminal differentiation and in almost complete granule cells loss (K,P). Aberrantly migrating neurons can still be detected by immunostaining for TuJ1 (B,G,L,Q). Inset in B shows expression of TuJ1 in the inner postmitotic, pre-migratory cell population (arrowheads), but not in the outer layers of the EGL in a P8 control mouse. Circles indicate the outer margin of the cerebellar folium. In L,Q, there is still a TuJ1-expressing cell population in the EGL present. Inset in Q shows a higher magnification of TuJ1-expressing cells above the level of dispersed Purkinje cells. Calbindin-positive Purkinje cells (C,H,M,R) are increasingly disarranged with dystrophic dendrites in Rb-deficient (H) and in Rb/p107 double mutants (M,R). Likewise, parvalbumin antiserum stains Purkinje cells (D,I,N,S) but also reveals a loss of interneurons of the molecular layer (arrowheads in D,I). Dystrophic Bergmann glia and an increasing astrogliosis are highlighted by GFAP immunostaining (E,J,O,T). (U-X) Representative drawings of midsagittally cut cerebella with indication of the areas (red square) shown at high magnification in A-T. Scale bar: 100 µm in A-T.

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