Expression of the ataxia-telangiectasia gene (ATM) product in human cerebellar neurons during development.

Ataxia-telangiectasia (A-T) is a hereditary disorder, exhibiting progressive cerebellar ataxia. We investigated the expression of the ATM protein in the human CNS. By western blotting, the ATM protein was detected in the cerebellar cortex, but not in the cerebral cortex, at the late gestational stage. Immunohistochemistry revealed that cerebellar neurons, particularly Purkinje cells, were markedly immunoreactive during late prenatal and early postnatal periods, followed by persistent and moderate reactivity in Purkinje cells. The ATM protein was distributed within the cytoplasm of Purkinje cells, but not within the nuclei. The ATM protein seems to play a role as a cytoplasmic protein in neurons of the cerebellar cortex.