Single Cell RNA sequencing of Adult Human Breast Epithelial Cells [C1_Individual_2]

Breast cancer arises from breast epithelial cells that acquire genetic alterations leading to subsequent loss of tissue homeostasis. Several distinct epithelial subpopulations have been proposed, but complete understanding of the spectrum of heterogeneity and differentiation hierarchy in the human breast remains elusive. Here, we used single-cell mRNA sequencing (scRNAseq) to profile the transcriptomes of 25,790 primary human breast epithelial cells isolated from reduction mammoplasties of seven individuals. Unbiased clustering analysis reveals the existence of three distinct epithelial cell populations, one basal and two luminal cell types, which we identify as secretory L1- and hormone-responsive L2-type cells. Pseudotemporal reconstruction of differentiation trajectories produc one continuous lineage hierarchy that closely connects the basal lineage to the two differentiated luminal branches. Our comprehensive cell atlas provides novel insights into cellular blueprint of the human breast epithelium and will form the foundation to understand how the system goes awry during breast cancer. Microfluidics-enabled Single Cell RNA sequencing libraries were generated for 3 adult human women using the Fluidigm C1 and sequenced on the Illumina HighSeq 2500