Localization of Mtss1 mRNA in the developing and adult cerebellum. A, B: In the newborn cerebellum, Mtss1 is found in a broad band of cells roughly outlining the nascent cerebellar cortex. Note that the deep cerebellar mass is relatively devoid of signal, as is the external granule cell layer. The latter can be readily recognized as a dense band at the surface in panel B, which shows counterstaining with Hoechst 33342. C-F: At p3 (C), p5 (D) and p8 (E, F), staining can be unambiguously attributed to cells in the inner part of the external granule cell layer, granule cells in the inner granule cell layer, and Purkinje neurons, which show an increasingly strong signal in the perikaryon. Note that the outer part of the EGL and the (prospective) white matter are devoid of signal. G-I: Between postnatal day 15 (G, H) and 21 (I), granule cells in the (internal) granule cell layer cease to express Mtss1. J, K: Adult. Staining is limited to Purkinje cell perikarya. All sections were obtained from the central vermis, except the one shown in panel I, which originates from the lateral vermis, and are cut in the sagittal plane. Anterior is to the left. Bar (in A, J) = 125 μm for panels D, E and insert in C; 250 μm for panels A, B, C, F, H and I; 500 μm for panels G and K; and 1 mm for panel J.