Human brain small extracellular vesicles contain selectively packaged, full-length mRNA

Area of Science:

• Neuroscience
• Molecular Biology
• Genomics

Background:

• Small extracellular vesicles (sEVs) are released by brain cells and contain nucleic acids.
• sEV-mediated exchange of molecules is a potential mechanism for spreading neuropathological changes in diseases like Alzheimer's disease (AD).

Purpose of the Study:

• To characterize the mRNA content of brain sEVs from non-diseased (ND) and AD individuals.
• To investigate cell-type-specific mRNA packaging in neural sEVs.
• To identify potential mechanisms of sEV loading.

Main Methods:

• Short- and long-read sequencing of mRNA from postmortem brain sEVs of ND and AD individuals.
• Analysis of sEV mRNA from cultured primary neurons, astrocytes, and microglia.
• Motif analysis of sEV-enriched mRNA isoforms.

Main Results:

• sEV transcriptomes are distinct from bulk brain tissue, enriched in ribosomal proteins and transposable elements (e.g., LINE-1).
• AD sEVs exhibit enriched inflammation-related mRNAs and depleted synaptic signaling mRNAs compared to ND sEVs.
• Neural sEVs contain predominantly full-length mRNA transcripts (approx. 80% with long-read sequencing).

Conclusions:

• Brain sEV mRNA is intact, selectively packaged, and significantly altered in Alzheimer's disease.
• These findings highlight the role of sEVs in intercellular communication and disease progression.
• Further research into RNA-binding proteins involved in sEV loading is warranted.