A Molecular Signature of Meaning? GADD45b Dissociates from Canonical Immediate Early Genes During Resolved Social Conflict

A targeted cross-species retro-analysis was conducted using three independent published datasets to test whether the DNA demethylase recruiter gadd45b occupies a functionally distinct category from canonical immediate early genes (IEGs). Whereas canonical IEGs generally respond to sufficiently intense neural or behavioral stimulation, gadd45b appears to be preferentially induced by genuine social engagement and social outcome resolution. In Betta splendens, gadd45bb (BSP_05575) was not differentially expressed after 20 minutes of fighting (logFC=+0.34, FDR=0.87) but increased after 60 minutes of sustained mutual assessment (logFC=+1.74, FDR=8.9×10⁻⁵) and reached its highest expression at or immediately following social outcome determination (logFC=+2.02, FDR=1.4×10⁻⁵). In zebra finch, singing-prevented adults—chronologically mature birds prevented from executing vocal learning—retained juvenile-like dendritic spine density in RA-projection neurons (p=0.774 versus juveniles; p=1.14×10⁻⁶ versus adults), while gadd45b expression distinguished singing adults from singing-prevented adults in HVC (p=0.014). Together with a zebrafish mirror-versus-real-opponent dissociation, these findings are consistent with gadd45b functioning not as a generic activity sensor but as a molecular mechanism engaged when socially assessed behavioral interactions are completed and their outcomes resolved. This property may bear on longstanding questions in neuroendocrinology, where the biological consequences of social conflict depend more strongly on social meaning than on physical intensity alone. The molecular machinery that translates social outcome into durable cellular change remains poorly characterized. Outcome-gated gadd45b-mediated DNA demethylation may represent a genomic form of metaplastic regulation that not only records experience but also modifies the chromatin landscape governing future responses to experience. This framework generates experimentally testable predictions regarding the molecular encoding of social outcome.