Distinct tau neuropathology and cellular profiles of a APOE3 Christchurch homozygote protected against Autosomal Dominant Alzheimer’s dementia

We describe in vivo follow-up PET imaging and postmortem findings from an autosomal dominant Alzheimer’s disease (ADAD) PSEN1 E280A carrier who was also homozygous for the APOE3 Christchurch (APOE3ch) variant and was protected against Alzheimer’s symptoms for almost three decades beyond the expected age of onset. We identified a distinct anatomical pattern of tau pathology with atypical accumulation in vivo and unusual postmortem regional distribution characterized by sparing in the frontal cortex and severe pathology in the occipital cortex. The frontal cortex and the hippocampus, less affected than the occipital cortex by tau pathology, contained Related Orphan Receptor B (RORB) positive neurons, homeostatic astrocytes and higher APOE expression. The occipital cortex, the only cortical region showing cerebral amyloid angiopathy (CAA), exhibited a distinctive chronic inflammatory microglial profile and lower APOE expression. Thus, the Christchurch variant impacts the distribution of tau pathology, modulates age at onset, severity, progression, and clinical presentation of ADAD, suggesting possible therapeutic strategies. We performed comparative gene expression profiling analysis using data obtained from three different brain regions (Frontal cortex, hippocampus and occipital cortex) of a post mortem brain of a patient carrier osf the autossomal dominant PSEN-1E280A mutation and homozygours fro the APOE3 Christchurch variant.