Cerebellar Ataxia in Patients with Mitochondrial DNA Disease: A Molecular Clinicopathological Study

摘要

Cerebellar ataxia is a prominent clinical symptom in patients with mitochondrial DNA (mtDNA) disease. Often this is progressive with onset in young adulthood. Here, we performed a detailed neuropathological investigation of the olivary-cerebellum in 14 genetically and clinically well-defined patients with mtDNA disease. Quantitative neuropathological investigation showed varying levels of loss of Purkinje cells, and neurons of the dentate nucleus and inferior olivary nuclei. Typically, focal Purkinje cell loss was present in patients with the m.3243A>G mutation due to the presence of microinfarcts with relative preservation of neuronal cell populations in olivary and dentate nuclei. In contrast, patients with the m.8344A>G mutation or recessive POLG mutations showed extensive and global neuronal cell loss in all 3 olivary-cerebellum areas examined. Molecular analysis of mutated mtDNA heteroplasmy levels revealed that neuronal cell loss occurred independently of the level of mutated mtDNA present within surviving neurons. High levels of neuronal respiratory chain deficiency, particularly of complex I, were detected in surviving cells; levels of deficiency were greater in regions with extensive cell loss. We found a relationship between respiratory deficiency and neuronal cell density, indicating that neuronal cell death correlates with respiratory deficiency. These findings highlight the vulnerability of the olivary-cerebellum to mtDNA defects.