MicroRNA-34a as a Possible Functional Marker of the Innate Freezing Defensive Response

Innate defensive behaviors such as freezing and escape are crucial for animal survival. These behavioral responses are mediated by distinct neural circuits conserved across species. However, whether molecular signatures can selectively identify and regulate functional units underlying specific defensive strategies remains largely unexplored. MicroRNAs (miRNAs) are small, conserved, non-coding RNAs with region- and cell-type-specific expression in the brain, making them promising candidates for this role. Among them, miR-34a shows high specificity in a subset of GABAergic neurons in the dorsal raphe nuclei (DRN), modulating inhibitory transmission selectively in response to aversive stimuli. We combined optogenetic, pharmacological, and genetic approaches to investigate whether miR-34a contributes to the modulation of innate defensive responses to distinct visual threats. First, using optogenetics, we demonstrated that GABAergic activity in the DRN is necessary for expressing defensive behaviors in response to ethologically relevant visual stimuli—specifically, a sweeping stimulus that induces freezing and a looming stimulus that triggers shelter-directed escape. Next, we showed that pharmacological inhibition of miR-34a in the DRN selectively impairs the freezing response without affecting escape. Finally, genetic suppression of miR-34a, specifically in DRN GABAergic neurons, confirmed its selective role in modulating the freezing—but not the escape—response to visual threat. These findings suggest miR-34a is a molecular signature of specific neural circuits modulating distinct defensive behavioral outcomes.