Selective Transgenic Expression of Mutant Ubiquitin in Purkinje Cell Stripes in the Cerebellum

The ubiquitin-proteasome system (UPS) is one of the major mechanisms for protein breakdown in cells, targeting proteins for degradation by enzymatically conjugating them to ubiquitin molecules. Intracellular accumulation of ubiquitin-B⁺¹ (UBB⁺¹), a frameshift mutant of ubiquitin-B, is indicative of a dysfunctional UPS and has been implicated in several disorders, including neurodegenerative disease. UBB⁺¹-expressing transgenic mice display widespread labeling for UBB⁺¹ in brain and exhibit behavioral deficits. Here, we show that UBB⁺¹ is specifically expressed in a subset of parasagittal stripes of Purkinje cells in the cerebellar cortex of a UBB⁺¹-expressing mouse model. This expression pattern is reminiscent of that of the constitutively expressed Purkinje cell antigen HSP25, a small heat shock protein with neuroprotective properties.