ATXN3 and Spinocerebellar ataxia type 3: Thus, in the present study, we characterized the alterations in mitochondrial function and markers of biogenesis in two different MJD models, namely mitochondria isolated from the cerebellum and brainstem (two brain regions most affected in MJD) of CMVMJD135 transgenic mouse brains and a tetracycline-regulated PC6-3 cell line expressing ATXN3 Q108, versus Q28 control cells.