Abstract
The developing mammary gland depends on several transcription-dependent networks to define cellular identities and differentiation trajectories. Recent technological advancements that allow for single-cell profiling of gene expression have provided an initial picture into the epithelial cellular heterogeneity across the diverse stages of gland maturation. Still, a deeper dive into expanded molecular signatures would improve our understanding of the diversity of mammary epithelial and non-epithelial cellular populations across different tissue developmental stages, mouse strains and mammalian species. Here, we combined differential mammary gland fractionation approaches and transcriptional profiles obtained from FACS-isolated mammary cells to improve our definitions of mammary-resident, cellular identities at the single-cell level. Our approach yielded a series of expression signatures that illustrate the heterogeneity of mammary epithelial cells, specifically those of the luminal fate, and uncovered transcriptional changes to their lineage-defined, cellular states that are induced during gland development. Our analysis also provided molecular signatures that identified non-epithelial mammary cells, including adipocytes, fibroblasts and rare immune cells. Lastly, we extended our study to elucidate expression signatures of human, breast-resident cells, a strategy that allowed for the cross-species comparison of mammary epithelial identities. Collectively, our approach improved the existing signatures of normal mammary epithelial cells, as well as elucidated the diversity of non-epithelial cells in murine and human breast tissue. Our study provides a useful resource for future studies that use single-cell molecular profiling strategies to understand normal and malignant breast development.
Highlights
The heterogenous cellularity of solid tissues controls the specialized events needed for prompt transitions through various stages of development and tissue function
Molecular signature that allows for the resolution of population heterogeneity within the murine mammary gland, we employed two tissue dissociation protocols to selectively enrich for either epithelial cells and non-epithelial cells from mammary glands of adult, never pregnant, female mice (Supplementary Fig. S1A). scRNA-seq was performed on each of the enriched cells, and clustering analyses resolved fifteen total murine mammary clusters of cells, which were composed of a total of 15,359 cells isolated from both digestion strategies (Fig. 1A, B)
Such cluster identity classification indicated that utilization of Protocol #1 allowed for a 2.5-fold enrichment of murine mammary epithelial cells over Protocol #2, which yielded an 8-fold enrichment in murine non-epithelial cells (Supplementary Fig. S1B)
Summary
The heterogenous cellularity of solid tissues controls the specialized events needed for prompt transitions through various stages of development and tissue function. CA 95616, US of the developing gland begins with the ability to appreciate how its constituent parts coexist and maintain tissue homeostasis and milk production. Luminal cells comprise an array of distinct cellular states, which drive processes associated with milk production [8, 9]. Mammary fibroblasts, which reside in proximity to myoepithelial cells, contribute to branching expansion and epithelium survival [10, 11]. Immune cells play a role in branching morphogenesis of the mammary epithelium and tissue regression during postlactational involution [12, 13]. These diverse cell types sustain the plasticity of the mammary gland through successive
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
