Transcriptomic analyses reveal senescent and SnoRNA changes in B cells with age irrespective of vaccine-stimulation in mice.

Abstract

Abstract Aging is associated with a decline in immune function that is not fully understood. Transcriptomic analysis is a powerful tool to evaluate age-related changes, but has not yet been reported for B-cells. To address this, we performed RNA-seq analyses on purified B-cells from naïve or vaccinated BALB/c mice of varying ages with the goal of expression profiling by age as opposed to any ongoing immunostimulation. Mouse age groups were Y (young, 15–20 wks), MA (middle-aged, 68–81 wks), and O (older, 103–111 wks) ± intramuscular Flulaval injection (n=5). Sequencing was performed using Ion Torrent/Ion Proton System. PCR and phenotype analyses were performed to validate selected results. In naïve groups, 230 genes were significantly differentially expressed by MA and O compared to Y. Nine of these were also significant comparing MA and O to Y in vaccinated groups. These included protein-coding genes: senescence-associated Cdkn2a; NFκB-mediator Edaradd; Klk4, a kallikrein implicated in cancer; and 4921504E06Rik, a gene region linked to inflammatory disease. Non-coding genes included: pseudogenes Gm2619 and RP24-374C7.3; antisense Gm16028; and box C/D small nuclear (sno) RNAs, Snord123 and Snord1a. The latter genes were particularly interesting as box C/D snoRNAs regulate rRNAs through methylation, and changes in their expression levels occur with neurodegenerative disorders, inflammatory diseases, and cancer. Altered DNA methylation or epigenetic drift is implicated in both healthy aging and age-related dysfunction but exact mechanisms are unclear. Our results suggest that Snord123 and Snord1a play a previously unappreciated role as regulators of altered methylation patterns contributing to age-related immune decline in B-cells.