Project description:Pre-effector and pre-memory cells resulting from the first CD8+ T cell division in vivo exhibit low and high rates of proteasome degradative activities, respectively. These proteasome-induced metabolic consequences were mediated in part by asymmetric segregation of Myc during cell division. Taken together, these results suggest proteasome activity as a regulator of CD8+ T lymphocyte metabolism and fate specification.
Project description:During microbial infection, responding CD8+ T lymphocytes differentiate into heterogeneous subsets that together provide immediate and durable protection. To elucidate the dynamic transcriptional changes that underlie this process, we applied a single-cell RNA sequencing approach and analyzed individual CD8+ T lymphocytes sequentially throughout the course of a viral infection in vivo. Our analyses revealed a striking transcriptional divergence among cells that had undergone their first division and identified previously unknown molecular determinants controlling CD8+ T lymphocyte fate specification, including Ezh2, the catalytic component of the Polycomb Repressive Complex 2. Our data provide a revised model of terminal effector cell differentiation initiated by an early burst of transcriptional activity and subsequently refined by epigenetic silencing of transcripts associated with memory lymphocytes. These findings provide unexpected insights into tightly coupled transcriptional and epigenetic mechanisms underlying CD8+ T lymphocyte fate specification and highlight the power and necessity of single-cell approaches.
Project description:Cellular binary fate decisions require the progeny to silence genes associated with the alternative fate. The major subsets of alpha:beta T cells have been extensively studied as a model system for fate decisions. While the transcription factor RUNX3 is required for the initiation of Cd4 silencing in CD8 T cell progenitors, it is not required to maintain the silencing of Cd4 and other helper T lineage genes. The other runt domain containing protein, RUNX1, silences Cd4 in an earlier T cell progenitor, but this silencing is reversed whereas the gene silencing after RUNX3 expression is not reverse. Therefore, we hypothesized that RUNX3 and not RUNX1 recruits other factors that maintains the silencing of helper T lineage genes in CD8 T cells. To this end, we performed a proteomics screen of RUNX1 and RUNX3 to determine candidate silencing factors.
