No abstract

RNA-seq by poly(A) selection is currently the most common protocol for whole transcriptome sequencing as it provides a broad, detailed, and accurate view of the RNA landscape. Unfortunately, the utility of poly(A) libraries is greatly limited when the input RNA is degraded, which is the norm for research tissues and clinical samples, especially when specimens are formalin-fixed. To facilitate the use of RNA sequencing beyond cell lines and in the clinical setting, we developed an exomecapture transcriptome protocol with greatly improved performance on degraded RNA. Capture transcriptome libraries enable measuring absolute and differential gene expression, calling genetic variants, and detecting gene fusions. Through validation against gold-standard poly(A) and Ribo-Zero libraries from intact RNA, we show that capture RNA-seq provides accurate and unbiased estimates of RNA abundance, uniform transcript coverage, and broad dynamic range. Unlike poly(A) selection and Ribo-Zero depletion, capture libraries retain these qualities regardless of RNA quality and provide excellent data from clinical specimens including formalin-fixed paraffin-embedded (FFPE) blocks. Systematic improvements across key applications of RNA-seq are shown on a cohort of prostate cancer patients and a set of clinical FFPE samples. Further, we demonstrate the utility of capture RNA-seq libraries in a patient with a highly malignant solitary fibrous tumor (SFT) enrolled in our clinical sequencing program called MI-ONCOSEQ. Capture transcriptome profiling from FFPE revealed two oncogenic fusions: the pathognomonic NAB2-STAT6 inversion and a therapeutically actionable BRAF fusion, which may drive this specific cancer's aggressive phenotype.

T cell maintenance in chronic infection and cancer follows a hierarchical order. Short-lived effector CD8 T cells are constitutively replaced from a proliferation-competent Tcf1-expressing progenitor population. This occurs spontaneously at low levels and increases in magnitude upon blocking PD-1 signaling. We explore how CD4 T cell help controls transition and survival of the progenitors and their progeny by utilizing single-cell RNA sequencing. Unexpectedly, absence of CD4 help caused reductions in cell numbers only among terminally differentiated cells while proliferation-competent progenitor cells remained unaffected with regard to their numbers and their overall phenotype. In fact, upon restoration of a functional CD4 compartment, the progenitors began to regenerate the effector CD8 T cells. Thus, unlike memory T cells for which secondary expansion requires CD4 T cell help, this is not a necessity for proliferation-competent progenitor cells in dysfunctional populations. Our data therefore reveals that proliferation-competent cells in dysfunctional populations show a previously unrecognized uncoupling of CD4 T cell help that is otherwise required by conventional memory T cells.