Direct cell-to-cell transmission of retrotransposons

Area of Science:

• Molecular Biology
• Genetics
• Evolutionary Biology

Background:

• Transposable elements (TEs) are abundant genomic components, typically confined to their cell of origin.
• Endogenous retroviruses are a known exception, capable of germline transmission.
• Conventional retroviral entry relies on a fusogenic Envelope protein.

Purpose of the Study:

• To investigate a novel transmission mechanism of LTR retrotransposons from somatic cells to the germline in Drosophila.
• To identify the molecular components and pathways involved in this noncanonical transfer.
• To explore the evolutionary implications of this transmission route.

Main Methods:

• Genetic analysis in Drosophila melanogaster.
• High-resolution imaging techniques, including electron microscopy.
• Biochemical assays to study protein localization and function.

Main Results:

• Identified LTR retrotransposons infecting the germline from somatic cells in the Drosophila ovary.
• Discovered a short transmembrane protein, sORF2, enabling Envelope-independent transfer of retrotransposon capsids.
• sORF2 facilitates direct transfer via invasive somatic cell protrusions into the oocyte.
• sORF2-like proteins are conserved across insect retrotransposons and found in other viruses.

Conclusions:

• A novel, Envelope-independent transmission mechanism for retrotransposons has been elucidated.
• This mechanism involves sORF2-mediated cell-cell transfer, bridging somatic and germline cells.
• The findings highlight a shared transmission strategy between retrotransposons and non-enveloped viruses, impacting host-pathogen evolution and soma-germline interactions.