PI Seminar Series
Speaker: Alexandra-Chloé Villani, Broad Institute of MIT and Harvard
Venue: Baddiley Clark Seminar Room
Date: Wednesday 23rd September 2015
Chloe Villani will present:
'Discovery of dendritic cell sub-populations in human blood
by single cell RNA-sequencing'
Following-up a decade of successful disease susceptibility loci identification, the next challenge remains translating these findings to biological understanding of disease. Identifying cells in which these loci are expressed and analyzing individual cells' roles in health and disease are critical to this endeavor. Dendritic cells (DC), which have historically been defined through surface marker analysis, play a critical role in a host's response to pathogens and in the immune responses characterizing cancer, inflammatory and infectious diseases. To discover DC subtypes in a more unbiased approach, we used single cell RNA-seq (scRNA-seq) to profile the transcriptome of 1056 single human blood DCs isolated from a healthy individual. While supervised analysis of DC markers effectively classified the 4 known populations (BDCA2+ (IL3RA), BDCA1+ (CD1C), BDCA3+ (CLEC9A), CD16+ (FCGR3A)), unsupervised analysis re-discovered all 4 subsets through a 630-discriminative gene signature in addition to highlighting novel heterogeneity within subsets. Multi-dimensional classification analysis of the first 384 single cells sequenced identified 26 outlier cells not clustering with any of the 4 known subsets. These outliers displayed a unique expression signature and a shared signature with BDCA2+ and BDCA3+ lineages. Using cell surface markers identified by scRNA-seq, we sorted and validated the existence of these cells in 10 additional healthy donors, showing they represent 0.06% of the PBMCs population in the blood and 2-3% of the DC populations across all 10 donors tested. Isolation and profiling of an additional 384 single cell outliers, together with functional experiments, enabled a deeper characterization of their phenotype. Together these analyses provide a comprehensive view of the DC landscape in blood, revealing new signatures and markers for the 4 known populations, novel subtypes within the known populations, and new rare populations of DCs.
Chair: Dr Muzz Haniffa