Alpha-synuclein seeding shows a wide heterogeneity in multiple system atrophy

Area of Science:

• Neuroscience
• Biochemistry
• Pathology

Background:

• Multiple system atrophy (MSA) is a neurodegenerative disease with variable clinical presentations.
• The distribution of alpha-synuclein pathology correlates with symptoms, but doesn't fully explain disease heterogeneity.
• Variability in alpha-synuclein seeding activity is hypothesized to drive clinical differences in MSA.

Purpose of the Study:

• To develop reliable cell-free assays for detecting alpha-synuclein seeding activity in MSA.
• To investigate the heterogeneity of alpha-synuclein seeding between different MSA patients and brain regions.
• To establish a framework for sub-classifying MSA based on seeding properties.

Main Methods:

• Systematic evaluation of 168 reaction buffers to optimize alpha-synuclein amplification.
• Validation of optimal conditions in a cohort of 40 neuropathologically confirmed cases (15 MSA).
• Multi-region analysis of alpha-synuclein seeding in 13 brain regions from 6 MSA cases.

Main Results:

• Novel buffer conditions enable reliable detection and strain-specific analysis of MSA-derived alpha-synuclein seeding.
• MSA brains were sub-categorized into high, intermediate, and low seeders based on seeding activity.
• Significant regional heterogeneity in alpha-synuclein seeding was observed within individual MSA brains.

Conclusions:

• Identified unexpected differences in seed-competent alpha-synuclein in comparable MSA brains.
• Revealed substantial heterogeneity in seeding activity between different brain regions within individuals.
• Proposed a new subclassification of MSA based on alpha-synuclein biochemical heterogeneity, aiding diagnostic assay development.