Abstract

Spatial transcriptomics reveal basal differences in nucleus accumbens gene profiles associated with temperament: studies in a rat model of emotional reactivity

Waselus M, Hebda-Bauer EK, Koonse S, Dai M, Meng F, Akil H, Watson SJ
52nd Annual Meeting of Society for Neuroscience. 2023.

Differences in emotionality and reactivity to the environment have been modeled using selectively-bred lines of high- and low-responder rats (bHR and bLR, respectively), which exhibit differences in exploratory locomotion, propensity to self-administer drugs of abuse, and anxiety-like behaviors. Anatomical methods (e.g., radioactive in situ hybridization) have implicated specific transcripts and brain regions in these behavioral differences, yet classical anatomical tools limit the number of genes examined. Expression profiling (e.g., bulk RNAseq) yielded profound bHR-bLR differences, however more anatomically precise expression profiling approaches are needed to capture regionally defined gene expression differences. Spatial transcriptomic solutions (e.g., Visium-FF, 10X Genomics) combine RNAseq with spatial registration to provide an unbiased global picture of RNA expression with anatomical specificity. Brains from our selective breeding colony (68th generation) were used to examine bHR/bLR differences in basal gene expression. We previously showed significant differences between the lines, including several immediate early genes (IEGs) exhibiting higher expression in the dorsal hippocampus (dHC) of bHRs vs bLRs. In these same rats, we examined the nucleus accumbens (NAc) while delineating differences between the core (NAcC) and shell (NAcS) regions. Differential gene expression was found between the NAcC and NAcS. Both bred lines exhibit higher calcium-binding protein calbindin 1 (Calb1) expression in the NAcC vs NAcS, while neurotensin (Nts) is more abundant in the NAcS vs NAcC. Differences between bHR-bLR were also found. As in the dHC, IEGs Arc and Egr1/zif-268 exhibited higher NAc expression in bHRs vs bLRs, though these differences were restricted to the NAcC, with no IEG differences in the NAcS. In addition, bHRs (vs bLRs) exhibited higher expression of the soluble epoxide hydrolase (Ephx2) in both the NAcC and NAcS, while increased levels of crystallin, alpha B (Cryab) in bHRs were limited to the NAcC. bLR rats expressed patatin-like phospholipase domain containing 1 (Pnpla1) in the NAcC and NAcS, while very little expression was seen in bHRs. Given that many of these genes are associated with inflammatory processes, further investigation of inflammatory pathways and related genes will be examined in both the dHC and NAc. Thus, the unbiased investigation of bHR/bLR brain differences using the Visium platform promises to be a valuable tool for elucidating differences in gene expression and enables subsequent, more refined future anatomical queries aimed at understanding the neurobiology of temperament.