Detection of pro-apoptotic Bax∆2 proteins in the human cerebellum.

Bax∆2 is a pro-apoptotic protein originally discovered in colon cancer patients with high microsatellite instability. Unlike most pro-apoptotic Bax family members, Bax∆2 mediates cell death through a non-mitochondrial caspase 8-dependent pathway. In the scope of analyzing the distribution of Bax∆2 expression in human tissues, we examined a panel of human brain samples. Here, we report four cerebellar cases in which the subjects had no neurological disorder or disease documented. We found Bax∆2 positive cells scattered in all areas of the cerebellum, but most strikingly concentrated in Purkinje cell bodies and dendrites. Two out the four subjects tested had strong Bax∆2-positive staining in nearly all Purkinje cells; one was mainly negative; and one had various levels of positive staining within the same sample. Further genetic analysis of the Purkinje cell layer, collected by microdissection from two subjects, showed that the samples contained G7 and G9 Bax microsatellite mutations. Both subjects were young and had no diseases reported at the time of death. As the distribution of Bax∆2 is consistent with that known for Baxα, but in a less ubiquitous manner, these results may imply a potential function of Bax∆2 in Purkinje cells.