Using quantitative polymerase chain reaction techniques, we measured circulating cell-free mitochondrial DNA (mtDNA) in cerebrospinal fluid (CSF) from study participants, selected from a cohort of 282 subjects, who were classified according to their concentrations of amyloid β1-42, total tau, and phosphorylated tau and by the presence or absence of dementia, into asymptomatic subjects at risk of AD, symptomatic patients diagnosed with sporadic AD, presymptomatic subjects carrying pathogenic PSEN1 mutations, and patients diagnosed with frontotemporal lobar degeneration (FTLD).
DNA methylation was analyzed in selected regions of MAPT, APP, and PSEN1 in the frontal cortex and hippocampus of controls (n=26) and those with Alzheimer disease at Stages I to II (n=17); Alzheimer disease at Stages III to IV (n=15); Alzheimer disease at Stages V to VI (n=12); argyrophilic grain disease (n=10); frontotemporal lobar degeneration linked to tau mutations (n=6); frontotemporal lobar degeneration with ubiquitin-immunoreactive inclusions (n=4); frontotemporal lobar degeneration with motor neuron disease (n=3); Pick disease (n=3); Parkinson disease (n=8); dementia with Lewy bodies, pure form (n=5); and dementia with Lewy bodies, common form (n=15).
These findings suggest that the insR352 PSEN1 is not pathogenic, and the IVS1+1G-->A mutation in PGRN causes FTDP associated with FTLD-U pathology and represents a new class of neurodegenerative disease--the 'hypoprogranulinopathies'.