W1. POSTPARTUM STRESS CAUSES TRANSCRIPTOMIC AND EPITRANSCRIPTOMIC CHANGES IN THE BASOLATERAL AMYGDALA OF RAT DAMS

Background Maternal postpartum stress caused by low resource parenting can produce enduring affective and stress-reactivity phenotypes in offspring, yet the effects on the maternal brain are largely unexplored. We aimed to define how postpartum stress reshapes isoform usage and the epitranscriptomic landscape in the female rat basolateral amygdala (BLA). Methods We collected BLA tissue from postpartum female rats parenting in a low resource or control environment (n=10). Poly(A)+ RNA was profiled using ONT direct RNA sequencing on the PromethION platform. Reads were basecalled and aligned to the rat reference genome GRCr8 using Dorado. Annotation at the gene and isoform level was performed with Bambu. We performed differential gene expression, differential isoform expression, and isoform-switching analyses, and leveraged raw-signal features to infer stress-associated epitranscriptomic signatures. Pathway and gene set enrichment was used to contextualize regulated programs. Results Direct RNA sequencing yielded long reads spanning full transcripts, enabling isoform-resolved quantification and simultaneous detection of stress-linked RNA features from the same dataset. Postpartum stress was associated with coordinated changes in BLA expression profile, resulting in differential expression of hundreds of genes and isoforms. These findings included isoform shifts within stress- and synapse-related pathways. Distinct RNA signatures across thousands of transcriptomic sites were also observed for m6A, m5C, and pseU modifications, indicating large-scale alterations in the epitranscriptomic following postpartum stress. Discussion These direct RNA sequencing data provide an integrated view of how postpartum stress modulates both isoforms and RNA modifications in the maternal BLA. Future directions include expansion to additional amygdala subnuclei and time points, addition of cell-type resolution, and validation of priority isoforms and modification sites with targeted long-read sequencing and orthogonal biochemical assays.