Early lineage segregation of multipotent embryonic mammary gland progenitors [RNA-seq I]
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ABSTRACT: The mammary gland (MG) is composed of basal cells (BCs) and luminal cells (LCs). While it is generally believed that MG arises from embryonic multipotent progenitors (EMPs), it remains unclear when lineage restriction occurs and what are the mechanisms responsible for the switch from multipotency to unipotency during MG morphogenesis. Here, we performed multicolor lineage tracing and assessed the fate of single progenitors and demonstrated the existence of a developmental switch from multipotency to unipotency during embryonic MG development. Molecular profiling and single cell RNA-seq revealed that EMPs express a unique hybrid basal and luminal signature and the factors associated with the different lineages. Sustained p63 expression in EMPs promotes unipotent BC fate and was sufficient to reprogram adult LCs into BCs by promoting an intermediate hybrid multipotent like state. Altogether, this study identifies the timing and the mechanisms mediating the early lineage segregation of multipotent progenitors during MG development.
Project description:The mammary gland (MG) is composed of basal cells (BCs) and luminal cells (LCs). While it is generally believed that MG arises from embryonic multipotent progenitors (EMPs), it remains unclear when lineage restriction occurs and what are the mechanisms responsible for the switch from multipotency to unipotency during MG morphogenesis. Here, we performed multicolor lineage tracing and assessed the fate of single embryonic progenitors during mouse MG development. We demonstrated the existence of a developmental switch from multipotency to unipotency during embryonic MG development. Molecular profiling and single cell RNA-seq revealed the hybrid gene expression of EMPs, and the gene trajectory and lineage segregation occurring during MG development. In situ characterization showed that one of the earliest signs of lineage segregation consists in the restricted expression of p63 in the future BCs. Sustained p63 expression during MG development promotes unipotent BC fate in EMPs. Altogether, this study identifies the timing and the mechanisms mediating the switch from multipotency to unipotency during MG development. To understand the molecular mechanisms regulating multipotency during embryonic development, we isolated EMPs by FACS at E14, performed their transcriptional profiling by microarray and compared their transcriptome to adult BCs and LCs
Project description:The mammary gland (MG) is composed of basal cells (BCs) and luminal cells (LCs). While it is generally believed that MG arises from embryonic multipotent progenitors (EMPs), it remains unclear when lineage restriction occurs and what are the mechanisms responsible for the switch from multipotency to unipotency during MG morphogenesis. Here, we performed multicolor lineage tracing and assessed the fate of single embryonic progenitors during mouse MG development. We demonstrated the existence of a developmental switch from multipotency to unipotency during embryonic MG development. Molecular profiling and single cell RNA-seq revealed the hybrid gene expression of EMPs, and the gene trajectory and lineage segregation occurring during MG development. In situ characterization showed that one of the earliest signs of lineage segregation consists in the restricted expression of p63 in the future BCs. Sustained p63 expression during MG development promotes unipotent BC fate in EMPs. Altogether, this study identifies the timing and the mechanisms mediating the switch from multipotency to unipotency during MG development. To understand the molecular mechanisms regulating multipotency during embryonic development, we isolated EMPs by FACS at E14, performed their transcriptional profiling by microarray and compared their transcriptome to adult BCs and LCs
Project description:Glandular epithelia including the mammary gland (MG) and the prostate are composed of basal cells (BC) and luminal cells (LC). Lineage tracing demonstrates that many glandular epithelia initially develop from multipotent basal stem cells (BaSCs) that are replaced in adult life by distinct pool of unipotent stem cells (SCs). However, adult unipotent BaSC can reactivate multipotency and give rise to LCs upon transplantation or oncogene expression, demonstrating the important plasticity of BaSCs in regenerative and pathological conditions, and suggesting that an active mechanism restricts multipotency in BaSCs during physiological conditions. The nature of this mechanism is currently unknown. Here, we assess whether basal and luminal cell-cell communication restricts multipotency in glandular epithelia. To this end, we performed lineage tracing of BCs together with the ablation of LCs in different adult glandular epithelia including MG, prostate, sweat glands and salivary glands and assessed the fate of BaSCs overtime. Interestingly, ablation of LCs reactivated multipotency in unipotent adult BaSCs from multiple epithelia. To understand the molecular mechanisms that controls multipotency in adult BaSCs, we performed population bulk-RNA-seq and single cell RNA-seq of FACS isolated adult mammary epithelial cells after LC ablation. Upon LC ablation, adult BCs activate a hybrid basal and luminal differentiation program before giving rise to LC, reminiscent of the genetic program that regulate multipotency during embryonic development. Different signaling pathways including Notch, Wnt and Egfr were activated in BaSC and their progeny following LC ablation and blocking these pathways inhibited adult BC multipotency. Altogether, our study demonstrates that heterotypic LC and BC communication is essential to maintain lineage fidelity in glandular epithelial SC during homeostasis and uncovers the lineage trajectory and signaling pathways that promote multipotency during tissue repair.
Project description:Sweat glands are abundant glands of our body and essential for thermoregulation. Like mammary glands, they originate from epidermal progenitors. However, they display few signs of cellular turnover, and whether they have stem cells and tissue regenerative capacity remain largely unexplored. Here we address these issues. Using lineage-tracing, we identify multipotent progenitors in sweat duct that transition to unipotency after developing the sweat gland. In characterizing four adult stem cell populations of glandular skin, we show that they display distinct regenerative capabilities and remain unipotent when healing epidermal, myoepithelial-specific and luminal-specific injuries. We devise purification schemes, isolate and transcriptionally profile progenitors. Exploiting molecular differences between sweat and mammary glands, we show that only some progenitors regain multipotency to produce de novo ductal and glandular structures, but that these can retain their identity even within certain foreign microenvironments. Our findings provide new concepts about glandular stem cells and sweat gland biology. 10 samples from mouse paw pads were analyzed
Project description:The mammary gland epithelium is composed of basal cells (BC) and luminal cells (LC). Lineage tracing demonstrates that many glandular epithelia initially develop from multipotent basal stem cells (BaSCs) that are replaced in adult life by distinct pool of unipotent stem cells. However, adult unipotent BaSC can reactivate multipotency and give rise to LCs upon transplantation or oncogene expression, demonstrating the important plasticity of BaSCs in regenerative and pathological conditions, and suggesting that an active mechanism restricts multipotency in BaSCs during physiological conditions. Here, we assess whether basal and luminal cell-cell communication restricts multipotency in glandular epithelia.
Project description:Sweat glands are abundant glands of our body and essential for thermoregulation. Like mammary glands, they originate from epidermal progenitors. However, they display few signs of cellular turnover, and whether they have stem cells and tissue regenerative capacity remain largely unexplored. Here we address these issues. Using lineage-tracing, we identify multipotent progenitors in sweat duct that transition to unipotency after developing the sweat gland. In characterizing four adult stem cell populations of glandular skin, we show that they display distinct regenerative capabilities and remain unipotent when healing epidermal, myoepithelial-specific and luminal-specific injuries. We devise purification schemes, isolate and transcriptionally profile progenitors. Exploiting molecular differences between sweat and mammary glands, we show that only some progenitors regain multipotency to produce de novo ductal and glandular structures, but that these can retain their identity even within certain foreign microenvironments. Our findings provide new concepts about glandular stem cells and sweat gland biology.
Project description:Breast cancer is the most frequent cancer in women and consists of heterogeneous types of tumours that are classified into different histological and molecular subtypes1-3. Pik3ca and p53 are the two most frequently mutated genes and are associated with different types of human breast cancers4. The cellular origin and the mechanisms leading to Pik3ca-induced tumour heterogeneity remain unknown. Here, we used a genetic approach in mice to define the cellular origin of Pik3ca-derived tumours and its impact on tumour heterogeneity. Surprisingly, oncogenic Pik3ca-H1047R expression at physiological levels5 in basal cells (BCs) using K5CREERT2 induced the formation of luminal ER+PR+ tumours, while its expression in luminal cells (LCs) using K8CREERT2 gave rise to luminal ER+PR+ tumours or basal-like ER-PR- tumours. Concomitant deletion of p53 and expression of Pik3ca-H1047R accelerated tumour development and induced more aggressive mammary tumours. Interestingly, expression of Pik3ca-H1047R in unipotent BCs gave rise to luminal-like cells, while its expression in unipotent LCs gave rise to basal-like cells before progressing into invasive tumours. Transcriptional profiling of cells that have undergone cell fate transition upon Pik3ca-H1047R expression in unipotent progenitors demonstrate a profound oncogene-induced reprogramming of these newly formed cells and identified gene signatures, characteristic of the different cell fate switches that occur upon Pik3ca-H1047R expression in BC and LCs, which correlated with the cell of origin, tumour type and different clinical outcomes. Altogether our study identifies the cellular origin of Pik3ca-induced tumours and reveals that oncogenic Pik3ca-H1047R activates a multipotent genetic program in normally lineage-restricted populations at the early stage of tumour initiation, setting the stage for future intratumoural heterogeneity. These results have important implications for our understanding of the mechanisms controlling tumour heterogeneity and the development of new strategies to block PIK3CA breast cancer initiation. Luminal and basal cells, or tumour cells, from mice in which expression of PIK3CA-H1047R and YFP (and in some conditions loss of p53) was targeted in basal cells using K5CREERT2 or in luminal cells using K8CREERT2 were FACS isolated and RNA was extracted before being hybridized Affymetrix microarrays.
Project description:We report single cell RNA-seq data that reveals that Embryonic Multipotent Progenitors (EMPs) in the mammary gland express a unique hybrid basal and luminal signature associated with the different adult lineages.
Project description:Glandular epithelia, including mammary gland (MG) and prostate, are composed of luminal and basal cells. During embryonic development, glandular epithelia arise from multipotent stem cells (SCs) giving rise to basal and luminal cells. However, these multipotent SCs are replaced after birth by unipotent basal and unipotent luminal SCs. Different conditions, such as basal cell transplantation, luminal cell ablation, and oncogene expression, can reinduce multipotency in adult basal SC (BaSCs) of different glandular epithelia. The mechanisms regulating the reactivation of multipotency in BaSCs are incompletely understood. Here, we compared the transcriptional signature of BaSCs from MG and prostate in different conditions associated with multipotency in adult mice and uncovered that Collagen I expression was commonly upregulated across the different conditions associated with multipotency. Using MG and prostate organoids, we demonstrated that increasing collagen concentration or stiffness of the extracellular matrix (ECM) promote BaSC multipotency. Single cell RNA-seq of MG organoids in the presence of high concentration of Collagen I or in a stiffer ECM activate a hybrid bipotent state and uncovered a gene signature and signaling pathways associated with bipotent BaSCs. Finally, we demonstrated the importance of 1integrin/FAK/AP-1 axis in the regulation of BaSC multipotency in response to Col1 signaling and ECM stiffness. Altogether our study uncovers the key role of Collagen signaling and ECM stiffness in the regulation of multipotency in glandular epithelia.
Project description:Glandular epithelia, including mammary gland (MG) and prostate, are composed of luminal and basal cells. During embryonic development, glandular epithelia arise from multipotent stem cells (SCs) giving rise to basal and luminal cells. However, these multipotent SCs are replaced after birth by unipotent basal and unipotent luminal SCs. Different conditions, such as basal cell transplantation, luminal cell ablation, and oncogene expression, can reinduce multipotency in adult basal SC (BaSCs) of different glandular epithelia. The mechanisms regulating the reactivation of multipotency in BaSCs are incompletely understood. Here, we compared the transcriptional signature of BaSCs from MG and prostate in different conditions associated with multipotency in adult mice and uncovered that Collagen I expression was commonly upregulated across the different conditions associated with multipotency. Using MG and prostate organoids, we demonstrated that increasing collagen concentration or stiffness of the extracellular matrix (ECM) promote BaSC multipotency. Single cell RNA-seq of MG organoids in the presence of high concentration of Collagen I or in a stiffer ECM activate a hybrid bipotent state and uncovered a gene signature and signaling pathways associated with bipotent BaSCs. Finally, we demonstrated the importance of 1integrin/FAK/AP-1 axis in the regulation of BaSC multipotency in response to Col1 signaling and ECM stiffness. Altogether our study uncovers the key role of Collagen signaling and ECM stiffness in the regulation of multipotency in glandular epithelia.