Phytochromes are evolutionarily conserved photoreceptors in bacteria, fungi, and plants. The prototypical phytochrome comprises an N-terminal photosensory module and a C-terminal histidine kinase signaling-output module. However, the plant phytochrome has been postulated to transduce light signals by interacting with a group of nodal Phytochrome-Interacting transcription Factors (PIFs) and triggering their degradation via the N-terminal photosensory module, while its C-terminal output module, including a Histidine Kinase-Related Domain (HKRD), is thought not to participate directly in signaling. Here, we show that the C-terminal module of Arabidopsis phytochrome B (PHYB) is unexpectedly sufficient to mediate the degradation of PIF3 and to induce a distinct set of PIF-regulated photosynthetic genes. These signaling functions require the HKRD and particularly its dimerization. A D1040V mutation, which disrupts the dimerization of HKRD and the interaction between the C-terminal module and PIF3, abrogates the early light signaling functions of PHYB in nuclear accumulation, photobody biogenesis, and PIF3 degradation. In contrast, disruption of the interaction between PIF3 and PHYB's N-terminal photosensory module has little effect on PIF3 degradation. Together, this study provides novel insight into the central mechanism of early phytochrome signaling that the C-terminal signaling-output module of PHYB interacts with PIF3 in the nucleus to mediate PIF3 degradation by light. Overall design: Whole seedling mRNA profiles of 100h dark-grown phyB-9 mutant and BCY overexpression line were generated by deep sequencing, in triplicate, using Illumina NextSeq 500
Mechanism of early light signaling by the carboxy-terminal output module of Arabidopsis phytochrome B.
Subject
View SamplesDuring development, a polarized sheet of epidermal cells undergoes stratification and differentiation to produce the skin barrier. Through mechanisms poorly understood, the process involves adhesion and Notch signaling. To elucidate how epidermal embryogenesis is governed, we conditionally targeted transcription factor serum response factor (SRF), which has been shown to be essential for proper epidermal differentiation in vitro and in vivo. Seeking mechanism, we identified actomyosin-related genes as well-known SRF targets downregulated shortly after ablation. We show that this results in a diminished cortical actomyosin network which fails to regulate the transition of cells from the basal proliferative layer to the suprabasal differentiating layer resulting in an inability of cells to properly execute stratification and differentiation.
Developmental roles for Srf, cortical cytoskeleton and cell shape in epidermal spindle orientation.
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View SamplesPolycomb protein group (PcG)-dependent trimethylation on H3-K27(H3K27me3) regulates identity of embryonic stem cells (SCs). How H3K27me3 governs adult SCs and tissue development is unclear. Here, we conditionally target H3-K27-methyltransferases Ezh2 and Ezh1 to address their roles in mouse skin homeostasis. Postnatal phenotypes appear only in doubly-targeted skin, where H3K27me3 is abolished, revealing functional redundancy in EZH1/2 proteins. Surprisingly, while Ezh1/2-null hair follicles (HFs) arrest morphogenesis and degenerate due to defective proliferation and increased apoptosis, epidermis hyperproliferates and survives engraftment. mRNA-microarray studies reveal that despite these striking phenotypic differences, similar genes are upregulated in HF and epidermal Ezh1/2-null progenitors. Featured prominently are a) PcG-controlled non-skin lineage genes, whose expression is still significantly lower than in native tissues, and b) the PcG-regulated Ink4a/Inkb/Arf locus. Interestingly, even though Ink4a/Arf/Ink4b genes are fully activated in HF cells, they only partially so in epidermal-progenitors. Importantly, transduction of Ink4b/Ink4a/Arf shRNAs restores proliferation/survival of Ezh1/2-null HF progenitors in vitro, pointing towards the relevance of this locus to the observed HF phenotypes. Our findings reveal new insights into Polycomb-dependent tissue control and provide a new twist to how different progenitors within one tissue respond to loss of H3K27me3.
EZH1 and EZH2 cogovern histone H3K27 trimethylation and are essential for hair follicle homeostasis and wound repair.
Sex, Age, Specimen part
View SamplesSweat 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.
Identification of stem cell populations in sweat glands and ducts reveals roles in homeostasis and wound repair.
Sex, Specimen part
View SamplesAlthough in vitro studies of embryonic stem cells have identified Polycomb repressor complexes (PRCs) as key regulators of differentiation, it remains unclear as to how PRC-mediated mechanisms control fates of multipotent progenitors in developing tissues. Here, we show that an essential PRC component, Ezh2, is expressed in epidermal progenitors, but diminishes concomitant with embryonic differentiation and with postnatal decline in proliferative activity. We show that Ezh2 controls proliferative potential of basal progenitors by repressing the Ink4A-Ink4B locus, and tempers the developmental rate of differentiation by preventing premature recruitment of AP1 transcriptional activator to the structural genes that are required for epidermal differentiation. Together, our studies reveal that PRCs control epigenetic modifications temporally and spatially in tissue-restricted stem cells by maintaining their proliferative potential and globally repressing undesirable differentiation programs, while selectively establishing a specific terminal differentiation program in a step-wise fashion.
Ezh2 orchestrates gene expression for the stepwise differentiation of tissue-specific stem cells.
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View SamplesHair Follicle regeneration relies on both epithelial components (bulge and hair germ cells) and a mesenchymal one (dermal papilla cells).
A two-step mechanism for stem cell activation during hair regeneration.
Specimen part
View SamplesmRNA expression data were collected from patients with brain tumor to improve diagnostic of gliomas on molecular level.
Neuronal and glioma-derived stem cell factor induces angiogenesis within the brain.
No sample metadata fields
View SamplesThe Epidermal Growth Factor Receptor (EGFR)/ligand system is centrally involved in multiple homeostatic functions of the epithelia. Epithelial cells are the primary targets of humanized antibodies and small molecule inhibitors against this system, whereby the constellation of skin-specific side effects of these drugs stems from a profound disturbance of keratinocyte biology. So far, the molecular mechanisms underlying these toxic events have been investigated only broadly. Here we show that keratinocyte response to anti-EGFR drugs comprises the development of a type 1 interferon (IFN) molecular signature including enhanced expression of IFN-kappa. Mechanistically, nuclear accumulation of IRF1 precedes this signature as well as the enhanced expression of a chemokine cluster we previously identified as a relevant pro-inflammatory component of EGFR inhibition. In fact, either silencing of IRF1 transcript expression, or antibody-mediated blockade of type 1 IFN receptor function and consequent abrogation of STAT1 activation, leads to impairment of this gene transcription profile. High levels of IRF1 and IFN-kappa can be clearly observed in the early skin lesions of patients treated with cetuximab. Type 1 IFN signaling could be crucially implicated in the triggering of the inflammatory mechanisms active in the skin of patients under treatment with anti-EGFR drugs.
Epidermal growth factor receptor inhibitors trigger a type I interferon response in human skin.
Specimen part, Cell line
View SamplesThe relationships between cancer cells and the microenvironment play a critical role in cancer growth and development. The bone stroma consists of mesenchymal stem cells (MSCs) and mature osteoblasts that promote cancer growth. Yet it is not completely understood what are the molecular processes guiding cancer cells progression to the bone. In this study, a co-culture assay and subsequent gene profiling arrays were used to compare the gene expression profile of a pre-osteoblastic cell line (MBA-15) with that of a mammary adenocarcinoma (DA3) cells. Following co-culture, cells were separated by magnetic beads based on the expression of CD326 antigen. RNA was purified and hybridized on gene expression array. The gene expression pattern changes were followed by qRT-PCR. We demonstrate that co-cultured DA3 cells express elevated levels of genes that regulate growth and responses to both hormonal stimulus and wounding, as well as reduced expression of genes related to lipid metabolism. Also, co-cultured pre-osteoblastic cells showed reduced expression of cell-junction genes. The study presents a simplified model system, composed of pre-osteoblastic and mammary cancer cells, that potentially mimics the molecular interactions in the tumor microenvironment which contribute to tumor-progression.
Molecular profiling of functional interactions between pre-osteoblastic and breast carcinoma cells.
Specimen part, Cell line
View SamplesTGFBR1*6A is a common hypomorphic variant of the type 1 Transforming Growth Factor Beta Receptor (TGFBR1), which has been associated with increased cancer risk in some studies. Although TGFBR1*6A is capable of switching TGF- growth inhibitory signals into growth stimulatory signals when stably transfected into MCF-7 breast cancer cells, TGFBR1*6A biological effects are largely unknown. To broadly explore TGFBR1*6A potential oncogenic properties, we assessed its impact on the migration and invasion of MCF-7 cells. We found that TGFBR1*6A significantly enhances MCF-7 cell migration and invasion in a TGF- signaling independent manner. We set up and performed a gene array using the conditions mimicking the cell migration experiments to determine which genes in the migratory pathway were differentially regulated between the MCF-7*6A cells and the MCF-7*9A (wild type transfected) cells. The gene array identified two downregulated genes in *6A compared to *9A that are involved in cell migration and invasion: ARHGAP5, encoding ARHGAP5, and FN1, encoding fibronectin-1 (FN1). We were subsequently able to use this information in further studies in the lab.
TGFBR1*6A enhances the migration and invasion of MCF-7 breast cancer cells through RhoA activation.
No sample metadata fields
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