Systems-guided forward genetic screen reveals critical role of the replication stress response protein ETAA1 in T cell clonal expansion

We have examined the role of the replication stress protein Etaa1 in mouse effector T cell expansion. While immune development and other steady state phenotypes are relatively normal in Etaa1 deficient mice, these mice have a selective defect in T cell expansion after vaccination or viral infection. To better determine the cause of this defect, we conducted RNA-seq analysis on Etaa1 wild-type or splice mutant LCMV-specific P14 CD8+ T cells at day 5 p.i. with LCMV-Armstrong. We find that mutant cells exhibit a strong enrichment of a p53 DNA damage signature within their transcriptome, and we independently validated this change by demonstrating increased staining for the DNA damage response factor gamma-H2AX within mutant T cells. Collectively these data suggest that Etaa1 plays a surprisingly specific role in preventing DNA damage accumulation within proliferating effector T cells. 5x10^4 CD45.1+ Etaa1+/+ or Etaa1 DEx2/DEx2 were injected i.v. into wild-type C57BL/6N mice that were subsequently infected with 2x10^5 pfu LCMV-Armstrong strain i.p. At day 5 p.i., spleens were isolated and pooled according to P14 genotype (typically 3-8 spleens per P14 genotype), and then a splenocyte suspension was sorted by FACS to isolate CD45.1+ CD8+ T cells.