Hormone-Responsive BMP Signaling Expands Myoepithelial Cell Lineages and Prevents Alveolar Precocity in Mammary Gland

Single-Cell Transcription Mapping of Murine and Human Mammary Organoids Responses to Female Hormones

During female adolescence and pregnancy, rising levels of hormones result in a cyclic source of signals that control the development of mammary tissue. While such alterations are well understood from a whole-gland perspective, the alterations that such hormones bring to organoid cultures derived from mammary glands have yet to be fully mapped. This is of special importance given that organoids are considered suitable systems to understand cross species breast development. Here we utilized single-cell transcriptional profiling to delineate responses of murine and human normal breast organoid systems to female hormones across evolutionary distinct species. Collectively, our study represents a molecular atlas of epithelial dynamics in response to estrogen and pregnancy hormones.

Single-cell transcription mapping of murine and human mammary organoids responses to female hormones

During female adolescence and pregnancy, rising levels of hormones result in a cyclic source of signals that control the development of mammary tissue. While such alterations are well understood from a whole-gland perspective, the alterations that such hormones bring to organoid cultures derived from mammary glands have yet to be fully mapped. This is of special importance given that organoids are considered suitable systems to understand cross species breast development. Here we utilized single-cell transcriptional profiling to delineate responses of murine and human normal breast organoid systems to female hormones across evolutionary distinct species. Collectively, our study represents a molecular atlas of epithelial dynamics in response to estrogen and pregnancy hormones.

Re-evaluation of the myoepithelial cells roles in the breast cancer progression

Over the past decades, luminal epithelial cell lineage has gained considerable attraction as the functionally milk-secreting units and as the most fruitful acreage for breast cancer launching. Recognition of the effective involvement of the myoepithelial cells in mammary gland development and in hampering tumorigenesis has renewed the interest in investigating the biological roles of this second main mammary lineage. The human breast is made up of an extensively branching ductal system intervening by copious lobular units. The ductal system is coated by a chain of luminal epithelial cells (LECs) situated on a layer of myoepithelial cells (MECs) and encompassed by a distinguished basement membrane. Ductal contractility during lactation is a well-known function delivered by the MECs however this is not the only assignment mediated by these cellular populations. It has been well appreciated that the MECs exhibit a natural paracrine power in defeating cancer development and advancement. MECs were found to express numerous proteinase inhibitors, anti-angiogenic factors, and tumour suppressors proteins. Additionally, MECs contributed effectively to maintaining the right luminal cells' polarization and further separating them from the adjacent stroma by making an integrated fence. Indeed, disruption of the MECs layer was reported to facilitate the invasion of the cancer cells to the surrounding stroma. Nonetheless, MECs were also found to exhibit cancer-promoting effects and provoke tumour invasion and dissemination by displaying distinct cancer chemokines. Herein in this review, we aimed to address the roles delivered by MECs in breast cancer progression and decipher the molecular mechanisms regulating proper MECs' physiology, integrity, and terminal differentiation.

CBLRR: a cauchy-based bounded constraint low-rank representation method to cluster single-cell RNA-seq data

The rapid development of single-cel+l RNA sequencing (scRNA-seq) technology provides unprecedented opportunities for exploring biological phenomena at the single-cell level. The discovery of cell types is one of the major applications for researchers to explore the heterogeneity of cells. Some computational methods have been proposed to solve the problem of scRNA-seq data clustering. However, the unavoidable technical noise and notorious dropouts also reduce the accuracy of clustering methods. Here, we propose the cauchy-based bounded constraint low-rank representation (CBLRR), which is a low-rank representation-based method by introducing cauchy loss function (CLF) and bounded nuclear norm regulation, aiming to alleviate the above issue. Specifically, as an effective loss function, the CLF is proven to enhance the robustness of the identification of cell types. Then, we adopt the bounded constraint to ensure the entry values of single-cell data within the restricted interval. Finally, the performance of CBLRR is evaluated on 15 scRNA-seq datasets, and compared with other state-of-the-art methods. The experimental results demonstrate that CBLRR performs accurately and robustly on clustering scRNA-seq data. Furthermore, CBLRR is an effective tool to cluster cells, and provides great potential for downstream analysis of single-cell data. The source code of CBLRR is available online at https://github.com/Ginnay/CBLRR.

BMP/SMAD1/5 Signaling in the Endometrial Epithelium Is Essential for Receptivity and Early Pregnancy

The biological processes that control endometrial receptivity and embryo implantation are critical for the successful outcome of pregnancy. The endometrium is the complex inner lining of the uterine wall that is under the cyclical control of estrogen and progesterone and is a site of intimate contact between mother and blastocyst. The bone morphogenetic signaling (BMP) pathway is a highly conserved signaling pathway that controls key cellular processes throughout pregnancy and exerts intracellular effects via the SMAD1/5 transcription factors. To delineate the endometrial compartment-specific roles of BMP signaling, we generated mice with epithelial-specific conditional deletion of SMAD1/5 using Lactoferrin-icre (Smad1flox/flox;Smad5flox/flox;Lactoferrin-cre, "Smad1/5 cKO"). Histological analysis of the reproductive tracts showed that Smad1/5 cKO mice were developmentally normal and displayed no defects in glandular morphology. In fertility analyses, single SMAD1 or SMAD5 deletion had no effect on fertility; however, double-conditional deletion of SMAD1 and SMAD5 resulted in severe subfertility. Timed mating analyses revealed endometrial receptivity defects in the Smad1/5 cKO mice beginning at 3.5 days post coitum (dpc) that perturbed embryo implantation at 4.5 dpc, as demonstrated by the detection of unattached blastocysts in the uterus, decreased COX2 expression, and FOXO1 cytoplasmic mislocalization. We also found that defects that arose during peri-implantation adversely affected embryonic and decidual development at 5.5 and 6.5 dpc. Thus, uterine epithelial BMP/SMAD1/5 signaling is essential during early pregnancy and SMAD1/5 epithelial-specific deletion has detrimental effects on stromal cell decidualization and pregnancy development.