In the cerebellum the prevalent population of neurons are granule cells, which express low levels of Afg3l2 and Spg7. Since it has been recently reported that AFG3L2 is involved in the SCA28 spinocerebellar ataxia [8], in which it is likely that Purkinje cells are affected, it is interesting to quantify the relative level of expression of these cells relative to the average cerebellar expression. The gene discussed is SPG7; the disease is cerebellar ataxia.