Studying the Impacts of Stress on Tet and Dnmt Expression in the Songbird’s Brain: Implications for Learning and Memory

Abstract

Stress is known to induce epigenetic modifications that can alter neural function and behavior. This thesis examines how an acute inflammatory stressor affects expression of DNA methylation and demethylation enzymes in the brain of a vocal-learning songbird, the zebra finch (Taeniopygia guttata), and the potential implications for learning and memory. Adult male zebra finches received LPS injections to simulate physiological stress. We quantified mRNA levels of Ten-Eleven Translocation (TET1, TET2) demethylation enzymes and DNA methyltransferases (DNMT1, DNMT3A, DNMT3B) in whole brain and in the song-dedicated HVC region using RT-qPCR, and assessed song behavior before and after stress. Results: Acute LPS challenge rapidly upregulated TET1 and TET2 transcripts in whole brain (TET1: p ≈ 0.049; TET2: p ≈ 0.023) and selectively increased DNMT3B (p < 0.01), indicating activation of both DNA demethylation and de novo methylation pathways. In striking contrast, within the HVC region—a key nucleus for song learning—TET1 expression was significantly downregulated by LPS (p ≈ 0.047) while TET2 remained unchanged. DNMTs were barely detectable in HVC. Behavioral analysis revealed that although overall song structure was preserved after stress, there were subtle but significant changes in acoustic features in LPS-treated birds, including shifts in pitch goodness, frequency, and duration, indicating fine-scale vocal motor instability. These changes align with the observed TET1 downregulation in the HVC, supporting a link between neuroepigenetic alterations and impaired vocal precision. Conclusion: Acute inflammatory stress leads to significant upregulation of TET1, TET2, and DNMT3B mRNA levels in the whole brain. In contrast, TET1 mRNA is specifically downregulated in the HVC—a critical song-learning region—indicating a localized suppression of demethylation activity that may impair neural plasticity and disrupt vocal precision.