To discover mechanisms that mediate plasticity in mammary cells, we characterized signaling networks that are present in the mammary stem cells responsible for fetal and adult mammary development. ...These analyses identified a signaling axis between FGF signaling and the transcription factor Sox10. Here, we show that Sox10 is specifically expressed in mammary cells exhibiting the highest levels of stem/progenitor activity. This includes fetal and adult mammary cells in vivo and mammary organoids in vitro. Sox10 is functionally relevant, as its deletion reduces stem/progenitor competence whereas its overexpression increases stem/progenitor activity. Intriguingly, we also show that Sox10 overexpression causes mammary cells to undergo a mesenchymal transition. Consistent with these findings, Sox10 is preferentially expressed in stem- and mesenchymal-like breast cancers. These results demonstrate a signaling mechanism through which stem and mesenchymal states are acquired in mammary cells and suggest therapeutic avenues in breast cancers for which targeted therapies are currently unavailable.
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•Sox10 labels and contributes to stem/progenitor activity in mammary cells•Sox10 drives EMT and delamination of clonogenic mammary cells at high levels•Sox10 expression and functional output are regulated by FGF signaling•Stem- and EMT-like breast cancers show the highest expression levels of Sox10
Dravis et al. report that Sox10 is specifically expressed in either stem-cell- or mesenchymal-like human breast cancers. The authors then demonstrate Sox10 can separately promote both stem/progenitor and mesenchymal-like states in mammary cells. They further identify FGF signaling as a key extrinsic mediator of Sox10 expression and function.
p53 activation prevents the proliferation of genetically unstable cells. Conversely, p53 antagonism by its transcriptional target, the E3 ubiquitin ligase MDM2, is critical for the viability of ...unstressed, cycling cells. We demonstrate that MDM2 induces the degradation of p53 in both the nucleus and the cytoplasm. As p53 and MDM2 accumulate in the nuclei of stressed cells, we investigated mechanisms enabling p53 activation despite the high MDM2 levels generated during a DNA‐damage response. We show that DNA damage destabilized MDM2 by a mechanism involving damage‐activated kinases and MDM2 auto‐ubiquitination. p53 was stable and transcriptionally active when MDM2 was unstable, but became unstable and inactive as the damage response waned and MDM2 stabilized. Importantly, blocking MDM2 destabilization in DNA‐damaged cells prevented p53 target gene activation. Our data reveal that controlled MDM2 degradation is an important new step in p53 regulation.
Impaired wound healing states lead to substantial morbidity and cost with treatment resulting in an expenditure of billions of dollars per annum in the US alone. Both chronic wounds and impaired ...acute wounds are characterized by excessive inflammation, enhanced proteolysis, and reduced matrix deposition. These confounding factors are exacerbated in the elderly, in part, as we report here, related to increased local and systemic tumor necrosis factor‐alpha (TNF‐α) levels. Moreover, we have used a secretory leukocyte protease inhibitor (SLPI) null mouse model of severely impaired wound healing and excessive inflammation, comparable to age‐related delayed human healing, to demonstrate that topical application of anti‐TNF‐α neutralizing antibodies blunts leukocyte recruitment and NFκB activation, alters the balance between M1 and M2 macrophages, and accelerates wound healing. Following antagonism of TNF‐α, matrix synthesis is enhanced, associated with suppression of both inflammatory parameters and NFκB binding activity. Our data suggest that inhibiting TNF‐α is a critical event in reversing the severely impaired healing response associated with the absence of SLPI, and may be applicable to prophylaxis and/or treatment of impaired wound healing states in humans.
Integrated into their bacterial hosts' genomes, prophage sequences exhibit a wide diversity of length and gene content, from highly degraded cryptic sequences to intact, functional prophages that ...retain a full complement of lytic-function genes. We apply three approaches-bioinformatics, analytical modelling and computational simulation-to understand the diverse gene content of prophages. In the bioinformatics work, we examine the distributions of over 50,000 annotated prophage genes identified in 1384 prophage sequences, comparing the gene repertoires of intact and incomplete prophages. These data indicate that genes involved in the replication, packaging, and release of phage particles have been preferentially lost in incomplete prophages, while tail fiber, transposase and integrase genes are significantly enriched. Consistent with these results, our mathematical and computational approaches predict that genes involved in phage lytic function are preferentially lost, resulting in shorter prophages that often retain genes that benefit the host. Informed by these models, we offer novel hypotheses for the enrichment of integrase and transposase genes in cryptic prophages. Overall, we demonstrate that functional and cryptic prophages represent a diversity of genetic sequences that evolve along a parasitism-mutualism continuum.
The mammary gland consists of cells with gene expression patterns reflecting their cellular origins, function, and spatiotemporal context. However, knowledge of developmental kinetics and mechanisms ...of lineage specification is lacking. We address this significant knowledge gap by generating a single-cell transcriptome atlas encompassing embryonic, postnatal, and adult mouse mammary development. From these data, we map the chronology of transcriptionally and epigenetically distinct cell states and distinguish fetal mammary stem cells (fMaSCs) from their precursors and progeny. fMaSCs show balanced co-expression of factors associated with discrete adult lineages and a metabolic gene signature that subsides during maturation but reemerges in some human breast cancers and metastases. These data provide a useful resource for illuminating mammary cell heterogeneity, the kinetics of differentiation, and developmental correlates of tumorigenesis.
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•Establishment of a developmental mammary transcriptome atlas•Chronology of mammary epithelial lineage bifurcation events•fMaSCs exhibit mixed lineage chromatin accessibility and gene expression patterns•fMaSC metabolic programs lost in differentiation are resurrected in breast cancer
Single-cell RNA sequencing of developing mouse mammary epithelia reveals the timing of lineage specification. Giraddi et al. find that fetal mammary stem cells co-express factors that define distinct lineages in their progeny and bear functionally relevant metabolic program signatures that change with differentiation and are resurrected in human breast cancers and metastases.
The first synthesis of hebelophyllene E is presented, along with assignment of its previously unknown relative configuration through synthesis of epi‐ent‐hebelophyllene E. Development of a catalytic ...enantioselective 2+2 cycloaddition of alkenes and allenoates provides access to the required chiral geminal dimethylcyclobutanes. Key to its success is the identification of a novel oxazaborolidine catalyst which promotes the cycloaddition in high enantioselectivities with good functional‐group tolerance (9 examples, up to 97:3 e.r.). Thus, a late‐stage cycloaddition using a fully functionalized alkene, followed by a diastereoselective reduction allows a concise entry to this class of natural products.
First design, then assign: The first synthesis of hebelophyllene E is presented, along with assignment of its previously unknown relative configuration through the synthesis of epi‐ent‐hebelophyllene E. Development of a catalytic enantioselective 2+2 cycloaddition of alkenes and allenoates, followed by diastereoselective conjugate reduction provides access to the required chiral geminal dimethylcyclobutane core.
Technological improvements enable single-cell epigenetic analyses of organ development. We reasoned that high-resolution single-cell chromatin accessibility mapping would provide needed insight into ...the epigenetic reprogramming and transcriptional regulators involved in normal mammary gland development. Here, we provide a single-cell resource of chromatin accessibility for murine mammary development from the peak of fetal mammary stem cell (fMaSC) functional activity in late embryogenesis to the differentiation of adult basal and luminal cells. We find that the chromatin landscape within individual cells predicts both gene accessibility and transcription factor activity. The ability of single-cell chromatin profiling to separate E18 fetal mammary cells into clusters exhibiting basal-like and luminal-like chromatin features is noteworthy. Such distinctions were not evident in analyses of droplet-based single-cell transcriptomic data. We present a web application as a scientific resource for facilitating future analyses of the gene regulatory networks involved in mammary development.
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•Performed single-nucleus (sn)ATAC-seq profiling of fetal and adult mammary cells•snATAC-seq reveals chromatin changes correlating with basal or luminal cell states•Cells with luminal- or basal-oriented chromatin features are evident before birth•A web resource for single-cell profile of embryonic and postnatal mammary development
The ability to deconstruct complex tissues into their constituent cell states and identify molecular mechanisms involved in cell differentiation is enabling deeper understanding of normal development and disease. Chung et al. use snATAC-seq to agnostically determine the chromatin states correlated with cell-state changes during embryonic and postnatal mammary development.
Abstract In periodontitis, a common chronic inflammatory condition, gram-negative-rich bacterial biofilms trigger, in susceptible individuals, perpetuating inflammation that results in extensive ...tissue damage of tooth supporting structures. To delineate immune cell-dependent mechanisms whereby bacterial challenge drives persistent destructive inflammation in periodontitis and other inflammatory diseases, we studied involved tissues ex vivo and investigated host cell responses to the periodontal pathogen Porphyromonas gingivalis , in vitro . Diseased lesions were populated by abundant Th17 cells, linked to infection, chronic inflammation/autoimmunity and tissue pathology. In vitro , P. gingivalis , particularly the more virulent strain W83, stimulated myeloid antigen presenting cells (APC) to drive Th17 polarization. Supernatants from myeloid APC exposed to P. gingivalis were capable of enhancing Th17 but not Th1 polarization. P. gingivalis favored the generation of Th17 responses by stimulating the production of Th17 related cytokines IL-1β, IL-6 and IL-23, but not Th1 related IL-12. By inducing NFκB activation, P. gingivalis promoted IL-1β, IL-6 and IL-12p40 production, but not IRF3 phosphorylation, connected to generation of the IL-12p35 chain, ultimately restricting formation of the intact IL-12 molecule. Promotion of Th17 lineage responses was also aided by P. gingivalis proteases, which appeared to differentially degrade pivotal cytokines. In this regard, IL-12 was largely degraded by P. gingivalis , whereas IL-1β was more resistant to proteolysis. Our data unveil multiple pathways by which P. gingivalis may orchestrate chronic inflammation, providing insights into interventional strategies.
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