Expression of the IP3R1 promoter-driven nls-LacZ transgene in Purkinje cell parasagittal arrays of developing mouse cerebellum

The cerebellar Purkinje cell monolayer is organized into heterogeneous Purkinje cell compartments that have different molecular compositions. Here we describe a transgenic mouse line, 1NM13, that shows heterogeneous transgene expression in parasagittal Purkinje cell arrays. The transgene consists of a nuclear localization signal (nls) fused to the b-galactosidase (lacZ) composite gene driven by the type 1 inositol 1,4,5-trisphosphate receptor (IP ₃R1) gene promoter. IP₃R1-nls-lacZ transgene expression was detected at a single Purkinje cell level over the surface of a whole-mount X-gal-stained cerebellum because of nuclear accumulation of the nls-lacZ activity. Developing cerebella of 1NM13 mice showed stripe-like X-gal staining patterns of parasagittal Purkinje cell subsets. The X-gal stripe pattern was likely determined by an intrinsic property as early as E15 and showed increasing complexity with cerebellar development. The X-gal stripe pattern was reminiscent of, but not identical to, the stripe pattern of zebrin II immunoreactivity. We designated the symmetrical X-gal-positive (transgene-positive, Tg⁺) Purkinje cell stripes about the midline as vermal Tg1⁺, Tg2(a, b)⁺ and Tg3(a, b)⁺ stripes and hemispheric Tg4(a, b)⁺, Tg5(a, b)⁺, Tg6(a, b, c) ⁺, and Tg7(a, b)⁺ stripes, where a, b, and c indicate substripes. We also assigned three parafloccular substripes Tg8(a, b, c) ⁺. The boundaries of X-gal stripes at P5 were consistent with raphes in the Purkinje cell layer through which granule cells migrate, suggesting a possible association of the X-gal stripes with raphe formation. Our results indicate that 1NM13 is a good mouse model with a reproducible and clear marker for the compartmentalization of Purkinje cell arrays.