Basic Science and Pathogenesis

Area of Science:

• Neurogenetics
• Alzheimer's Disease Research
• Human Genetics

Background:

• Early-Onset Alzheimer's Disease (EOAD) is a rare neurodegenerative disorder often linked to specific genetic mutations like PSEN1 A431E.
• The PSEN1 A431E mutation causes rapid disease progression, with patients typically showing symptoms around age 42.5 and dying within 7.5 years.
• Clinical variability exists even among families with the same mutation, prompting investigation into other genetic modifiers.

Purpose of the Study:

• To investigate the influence of Apolipoprotein E (APOE) alleles on the clinical phenotype of familial Early-Onset Alzheimer's Disease (EOAD) in patients with the PSEN1 A431E mutation.
• To determine if APOEε2 and APOEε4 alleles affect the age of symptom onset or initial clinical presentation in this EOAD cohort.

Main Methods:

• Evaluated 89 patients with familial EOAD exhibiting autosomal dominant inheritance patterns.
• Confirmed the PSEN1 A431E mutation via Sanger sequencing.
• Genotyped APOEε2 and APOEε4 alleles using real-time PCR and analyzed clinical correlations with descriptive statistics and regression models.

Main Results:

• A significant association was found between APOE alleles and age at symptom onset in PSEN1 A431E mutation carriers.
• APOEε4 carriers experienced a statistically significant delay in symptom onset by 4.15 years (p=0.00035).
• APOEε2 carriers showed a significant acceleration of symptom onset by 2.34 years (p=0.037), with no observed effect on initial clinical manifestation.

Conclusions:

• APOEε4 and APOEε2 alleles exhibit an inverse effect on symptom onset in EOAD patients with the PSEN1 A431E mutation, contrasting with their known roles in late-onset AD.
• APOEε4 delays, while APOEε2 accelerates, the age of symptom onset in this specific EOAD genetic context.
• These findings underscore the dual role of APOE alleles as genetic modifiers in EOAD, potentially enabling personalized risk assessment and targeted therapeutic strategies.