Profiling human breast epithelial cells using single cell RNA sequencing identifies cell diversity.

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 use 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 produces one continuous lineage hierarchy that closely connects the basal lineage to the two differentiated luminal branches. Our comprehensive cell atlas provides insights into the cellular blueprint of the human breast epithelium and will form the foundation to understand how the system goes awry during breast cancer

Single cell sequencing analysis reveals mammary epithelial cell diversity and regulation

The mammary epithelial system is a heterogeneous cellular compartment thought to be comprised of two major cell types, basal and luminal respectively, that are in flux throughout an individual’s life and require a stem cell compartment to maintain. Questions remain about the origin and nature of these stem cells, and how the constituent components of the gland interplay in order to maintain a healthy tissue or ultimately responds to cancer present. Through the usage of single cell microfluidic based experimental tools, we have been able to explore this relevant heterogeneity with single cell RNA sequencing (scRNA-seq) in human and mouse and single cell ATAC sequencing (scATAC-seq) in mouse. We highlight in both species the different basal and luminal cell types, with the stratification of the luminal compartment into hormone response or secretory cells. Additional relevant cell states present within the secretory luminal cell type manifest with tissue relevant consequences. Using scRNA-seq in human we present three major epithelial cell types, one basal and two distinct luminal referred to as L1 (Secretory) and L2 (Hormone Responsive). After applying pseudotemporal reconstruction, it is shown that the three populations interconnect in a developmental lineage with basal cells branching into the two luminal end points. In mouse, a similar three epithelial cell type structure is highlighted in the mammary gland with both scRNA-seq and scATAC-seq in an integrated analysis. The secretory luminal compartment is additionally stratified into luminal progenitor and lactation-committed progenitors, with distinct regulatory features underpinning each cell state through both cis and trans acting elements. Taken together, these results emphasize newly discovered heterogeneity in the luminal compartment of the mammary gland, challenging of previously held definitions of the mammary stem cell, and the underlying regulation of cell state

Quel type de prise en charge pour quelle efficacité chez les intervenants?

L’objectif de cette communication est d’exposer les résultats d’une étude menée auprès de professionnels qui sont intervenus dans le cadre de la fusillade de la place Saint Lambert à Liège le 13 décembre 2011. L’étude avait pour objectif d’évaluer l’impact à long terme de cet événement sur la vie privée et professionnelle des intervenants des services de secours. Pour ce faire, elle a été menée en 2013 à partir d’un listing reprenant les professionnels qui sont intervenus sur le terrain ce jour-là. 34 professionnels (médecins, infirmiers, ambulanciers et pompiers) ont participé à l’étude. Cette communication présentera les résultats à l’enquête ainsi que les conclusions qui peuvent en être tirées, notamment en matière de soutien et de son effet les plaintes somatiques des intervenants

Tumour heterogeneity and metastasis at single-cell resolution

Tumours comprise a heterogeneous collection of cells with distinct genetic and phenotypic properties that can differentially promote progression, metastasis and drug resistance. Emerging single-cell technologies provide a new opportunity to profile individual cells within tumours and investigate what roles they play in these processes. This Review discusses key technological considerations for single-cell studies in cancer, new findings using single-cell technologies and critical open questions for future applications

Diverse regulation of mammary epithelial growth and branching morphogenesis through noncanonical Wnt signaling.

The mammary gland consists of an adipose tissue that, in a process called branching morphogenesis, is invaded by a ductal epithelial network comprising basal and luminal epithelial cells. Stem and progenitor cells drive mammary growth, and their proliferation is regulated by multiple extracellular cues. One of the key regulatory pathways for these cells is the β-catenin-dependent, canonical wingless-type MMTV integration site family (WNT) signaling pathway; however, the role of noncanonical WNT signaling within the mammary stem/progenitor system remains elusive. Here, we focused on the noncanonical WNT receptors receptor tyrosine kinase-like orphan receptor 2 (ROR2) and receptor-like tyrosine kinase (RYK) and their activation by WNT5A, one of the hallmark noncanonical WNT ligands, during mammary epithelial growth and branching morphogenesis. We found that WNT5A inhibits mammary branching morphogenesis in vitro and in vivo through the receptor tyrosine kinase ROR2. Unexpectedly, WNT5A was able to enhance mammary epithelial growth, which is in contrast to its next closest relative WNT5B, which potently inhibits mammary stem/progenitor proliferation. We found that RYK, but not ROR2, is necessary for WNT5A-mediated promotion of mammary growth. These findings provide important insight into the biology of noncanonical WNT signaling in adult stem/progenitor cell regulation and development. Future research will determine how these interactions go awry in diseases such as breast cancer

Gut microbial and metabolomic profiles after fecal microbiota transplantation in pediatric ulcerative colitis patients

Ulcerative colitis is a chronic inflammatory disease of the colon that carries a significant disease burden in children. Therefore, new therapeutic approaches are being explored to help children living with this disease. Fecal microbiota transplantation (FMT) has been successful in some children with ulcerative colitis. However, the mechanism of its therapeutic effect in this patient population is not well understood. To characterize changes in gut microbial and metabolomic profiles after FMT, we performed 16S rRNA gene sequencing, shotgun metagenomic sequencing, virome analysis and untargeted metabolomics by gas chromatography-time of flight-mass spectrometry on stool samples collected before and after FMT from four children with ulcerative colitis who responded to this treatment. Alpha diversity of the gut microbiota increased after intervention, with species richness rising from 251 (S.D. 125) to 358 (S.D. 27). In responders, the mean relative abundance of bacteria in the class Clostridia shifted toward donor levels, increasing from 33% (S.D. 11%) to 54% (S.D. 16%). Patient metabolomic and viromic profiles exhibited a similar but less pronounced shift toward donor profiles after FMT. The fecal concentrations of several metabolites were altered after FMT, correlating with clinical improvement. Larger studies using a similar multi-omics approach may suggest novel strategies for the treatment of pediatric ulcerative colitis

Defining the emergence of myeloid-derived suppressor cells in breast cancer using single-cell transcriptomics

Myeloid-derived suppressor cells (MDSCs) are innate immune cells that acquire the capacity to suppress adaptive immune responses during cancer. It remains elusive how MDSCs differ from their normal myeloid counterparts, which limits our ability to specifically detect and therapeutically target MDSCs during cancer. Here, we sought to determine the molecular features of breast cancer-associated MDSCs using the widely studied mouse model based on the mouse mammary tumor virus (MMTV) promoter-driven expression of the polyomavirus middle T oncoprotein (MMTV-PyMT). To identify MDSCs in an unbiased manner, we used single-cell RNA sequencing to compare MDSC-containing splenic myeloid cells from breast tumor-bearing mice with wild-type controls. Our computational analysis of 14,646 single-cell transcriptomes revealed that MDSCs emerge through an aberrant neutrophil maturation trajectory in the spleen that confers them an immunosuppressive cell state. We establish the MDSC-specific gene signature and identify CD84 as a surface marker for improved detection and enrichment of MDSCs in breast cancers

Integrated Single-Cell Transcriptomics and Chromatin Accessibility Analysis Reveals Regulators of Mammary Epithelial Cell Identity

The mammary epithelial cell (MEC) system is a bilayered ductal epithelium of luminal and basal cells, maintained by a lineage of stem and progenitor populations. Here, we used integrated single-cell transcriptomics and chromatin accessibility analysis to reconstruct the cell types of the mouse MEC system and their underlying gene regulatory features in an unbiased manner. We define differentiation states within the secretory type of luminal cells, which forms a continuous spectrum of general luminal progenitor and lactation-committed progenitor cells. By integrating single-cell transcriptomics and chromatin accessibility landscapes, we identify cis- and trans-regulatory elements that are differentially activated in the specific epithelial cell types and our newly defined luminal differentiation states. Our work provides a resource to reveal cis/trans-regulatory elements associated with MEC identity and differentiation that will serve as a reference to determine how the chromatin accessibility landscape changes during breast cancer