Amyloid-mediated RNA uptake by sperm for embryonic delivery.

Functional amyloid fibrils in mammalian seminal fluid bind and traffic RNA into sperm, enabling amyloid-bound RNA delivery to the zygote after fertilization.

• Why it matters: Seminal fluid RNA is essential for embryonic development, but how extracellular RNA is transferred from seminal fluid to sperm and then to the zygote was unclear.
• What they did: Highly cationic peptides in seminal fluid phase separate with RNA to form amyloid fibrils, which are internalized by mammalian sperm shown by cryo-ET, volume EM, and live-cell imaging.
• The result: Biophysical and IVF experiments indicate amyloid-bound RNA reaches the zygote, where molecular chaperones can control RNA dissociation from amyloid fibrils, supporting amyloid fibrils as RNA-delivery tools during fertilization.