Glial cells gate small RNA transport from germline to brain during transgenerational epigenetic inheritance of behavior

In Caenorhabditis elegans, amphid sheath glia use SID-1 to gate Cer1 retrotransposon-bound small RNA transport from germline to neurons, enabling learned avoidance.

• Why it matters: It was unclear how circulating small RNA signals reach target tissues, especially how a germline-to-neuron pathway enables both learned behavior and transgenerational inheritance.
• What they did: The study identified SID-1 as acting in amphid sheath glia, where it is necessary and sufficient for learned avoidance, mediating uptake of germline-derived RNA and transcytosis to sensory neurons.
• The result: In neurons, the P11 target gene maco-1 is silenced, supporting a glial “filter” mechanism that gates small RNA access to the nervous system and parallels a mammalian blood-brain barrier.