(112) Bulk RNAseq of cardiac myosin-specific CD4 and CD8 T cells reveals distinct transcriptomic profiles between myocarditis-resistant and susceptible mice

Introduction/Rationale: We recently generated T cell receptor (TCR) transgenic (Tg) mice specific to cardiac myosin heavy chain-α (Myhc-α 334–352) on both myocarditis-resistant (C57BL/6) and susceptible (A/J) genetic backgrounds. While functional antigen-specific TCRs were expressed in both CD4⁺ and CD8⁺ T cells, the T cells from naïve Tg C57BL/6 mice did not respond to Myhc-α 334-352. In contrast, both cell types from A/J mice spontaneously responded to the antigen, suggesting their underlying molecular mechanisms might differ.

Methods: Using flow cytometrically sorted cells from naïve C57BL/6 and A/J Tg mice, we performed bulk RNA sequencing on CD4⁺ and CD8⁺ T cell subsets. Differentially expressed genes (DEGs), gene ontology (GO), and Kyoto encyclopedia of genes and genomes (KEGG) pathways, Gene set enrichment analysis (GSEA) of GO and KEGG, and transcription factor (TF) network analyses were performed to identify pathways and regulators of immune responses.

Results: Principal component analysis distinguished CD4⁺ from CD8⁺ T cells and revealed distinct transcriptomic profiles between C57BL/6 and A/J mice. KEGG enrichment analysis indicated downregulation of pathways related to viral myocarditis and autoimmune conditions in C57BL/6 compared to A/J mice. GSEA of GO revealed that negative regulation of heart contraction and positive regulation of cardiac muscle hypertrophy were negatively enriched in CD4⁺ T cells from C57BL/6 mice. TF network analysis revealed unique TFs that have a role in autoimmunity, T cell activation, tolerance, and regulatory T cells.

Conclusion: Our data provide new insights into the transcriptomic profiles that may contribute to the genetic resistance mechanisms for developing cardiac autoimmunity.