Progressive vulnerability of cortical synapses in α-synucleinopathy.

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Neurodegenerative Diseases

Background:

• Alpha-synuclein (α-syn) aggregates are key pathological hallmarks in neurodegenerative disorders such as Parkinson's disease and dementia with Lewy bodies.
• Cortical α-syn pathology is linked to cognitive decline, suggesting a disruption of neural connectivity.

Purpose of the Study:

• To investigate the progressive impact of α-syn pathology on synaptic connectivity within the frontal cortex.
• To identify specific synapse types vulnerable or resilient to α-syn accumulation and characterize underlying mechanisms.

Main Methods:

• High-resolution imaging (including electron microscopy) to assess synaptic structure and density.
• Gene expression analysis (ontology) in affected neurons to identify molecular pathways.
• Neuroanatomical connectivity mapping and electrophysiological recordings.

Main Results:

• Progressive loss and structural disruption of intracortical excitatory (VGLUT1+) synapses near α-syn aggregates.
• Synaptic α-syn accumulation correlated with synapse loss; altered gene expression suggested resilience mechanisms.
• Intratelencephalic (IT) projection neurons in layer V were vulnerable, while long-range excitatory (VGLUT2+) synapses were spared.
• Inhibitory (VGAT+) synapses showed late-stage modest impact; impaired excitatory transmission was confirmed electrophysiologically.

Conclusions:

• Intracortical synapses are a primary locus of connectivity disruption in α-synucleinopathies.
• Synapse-type specific vulnerabilities and resilience mechanisms are evident in the progression of these diseases.
• Understanding these synaptic changes is crucial for developing targeted therapies for cognitive decline in α-synucleinopathies.