Studies on the first described Alzheimer's disease amyloid beta mutant, the Dutch variant

Area of Science:

• Neuroscience
• Genetics
• Pathology

Background:

• Hereditary cerebral hemorrhage with amyloidosis, Dutch type (HCHWA-D), involves amyloid protein deposition in cerebral vessels and plaques.
• This amyloid protein is similar to amyloid beta (Abeta) found in Alzheimer's disease (AD), Down's syndrome, and cerebral amyloid angiopathy (CAA).

Purpose of the Study:

• To investigate the role of mutations in the amyloid beta-protein precursor (AbetaPP) gene in HCHWA-D and familial AD (FAD).
• To understand how different mutation locations within AbetaPP affect Abeta production, aggregation, and deposition.

Main Methods:

• Gene sequencing of AbetaPP in HCHWA-D patients to identify mutations.
• Analysis of mutations in familial AD pedigrees.
• Cell transfection studies to examine the impact of AbetaPP substitutions on Abeta production, secretion, and aggregation.

Main Results:

• A single mutation (Abeta E22Q) was identified in the AbetaPP gene of HCHWA-D patients.
• Mutations in the central Abeta region (residues 21-23) are associated with vasculotropic deposition.
• Mutations flanking the Abeta sequence enhance parenchymal plaque deposition, increase Abeta production or secretion of fibrillogenic Abeta1-42, and promote aggregation and toxicity.

Conclusions:

• The location of AbetaPP mutations significantly influences the type and location of amyloid deposition in the brain.
• Central AbetaPP mutations lead to increased aggregation, impaired clearance, and enhanced toxicity, contributing to HCHWA-D pathology.
• While genetic defects in AbetaPP are implicated in some forms of AD, other factors likely contribute to the majority of AD cases.