Transcriptional changes in murine keratinocyte harbouring heterozygous or homozygous R245W p53 mutation in vitro
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ABSTRACT: Human epidermis is colonized by clones carrying UV light induced p53 mutations, thought to be the origin of keratinocyte derived cancers, but the cellular mechanisms underlying the formation of these clones are not well understood. To address this we generated a new conditional knock-in mouse model bearing one of the hot spot mutations, R245W (R248W in human), targeted to the p53 locus, with its expression linked to a GFP reporter to enable lineage tracing. This mutation is one of the most frequently observed in cutaneous squamous cell carcinomas. We find that when induced in individual epidermal interfollicular progenitor cells the p53 mutant cells are dominant over wild type keratinocytes expanding to colonize the majority of the interfollicular epidermis. This process is accelerated by sub erythema doses ultraviolet light exposure. In vitro analysis of the trancriptomes can explain the intrinsic function driving clonal expansion.
Project description:The vitamin D receptor (VDR) regulates cell proliferation and differentiation including epidermal keratinocytes by modulating transcription of its target genes. We are investigating the role of VDR in epidermal stem cells and their progenies in the regeneration process of epidermis and hair in the skin. VDR null mice are utilized in which VDR is specifically deleted in keratin 14 (K14) expressing keratinocytes by Cre-lox strategy. The impact of VDR deletion was evaluated by comparison of VDR null mice with no cre littermate control mice. The VDR was abundantly expressed in potential epidermal stem cells including basal cells in interfollicular epidermis (IFE), and in CD34 expressing bulge keratinocytes in hair follicles. Gene expression profiles and subsequent pathway analysis of stem cell enriched keratinocyte populations revealed that the VDR deletion significantly suppressed β-catenin signaling as well as VDR signaling. The role of VDR in epidermal stem cells was studied during hair follicle cycling and wound healing processes. The epidermal stem cells were not appropriately stimulated by hair depilation, and did not reinitiate anagen in the hair follicles resulting in a failure of hair regrowth. In addition, the stem cells were not fully activated after full thickness wounds were generated in VDR null skin under a low calcium diet to suppress compensation pathways. Cell proliferation was not fully induced in potential stem cells located in both IFE and hair follicles near the wounding edges, and re-epithelialization rate was delayed in VDR null skin. Gene expression profiling of the wounded skin (3 days after injury) indicated that β-catenin signaling was not fully induced in VDR null skin comparable to that observed in β-catenin null mice. The β-catenin target genes including Axin2 and cell cycle regulators involved in epidermal stem cell function were not induced in the edges of the wound of VDR null skin. These results demonstrated that VDR plays an essential role in hair cycling and wound healing processes through regulation of β-catenin signaling in epidermal stem cells and their progenies. n=3 CON and KO (each sample contain RNA extracted from keratinocytes, which is isolated from VDR KO and littermate control skins excised from 3 mice)
Project description:RNA sequencing was performed on sorted populations of Lgr6-positive and Lgr6-negative keratinocytes from the interfollicular epidermis and the hair follicle/sebaceous gland, in order to determine the compartment-specific expression signatures of Lgr6+ progenitor cells.
Project description:Progenitor cells at the basal layer of skin epidermis play an essential role in maintaining tissue homeostasis and enhancing wound repair in skin. The proliferation, differentiation, and cell death of epidermal progenitor cells have to be delicately regulated, as deregulation of this process can lead to many skin diseases, including skin cancers. However, the underlying molecular mechanisms involved in skin homeostasis remain poorly defined. In this study, with quantitative proteomics approach, we identified an important interaction between KDF1 (Keratinocyte Differentiation Factor 1) and IKKα (IκB kinase α) in differentiating skin keratinocytes. Ablation of either KDF1 or IKKα in mice leads to similar but striking abnormalities in skin development, particularly in skin epidermal differentiation. With biochemical and mouse genetics approach, we further demonstrate that the interaction of IKKα and KDF1 is essential for epidermal differentiation. To probe deeper into the mechanisms, we find that KDF1 associates with a deubiquitinating protease, USP7 (Ubiquitin Specific Peptidase 7), and KDF1 can regulate skin differentiation through deubiquitination and stabilization of IKKα. Taken together, our study unravels an important molecular mechanism underlying skin tissue homeostasis and epidermal differentiation.
Project description:In this study we aim to determine the role of IL-4/STAT6 in gene expression in human keratinocytes using RNA-sequencing approach. Human keratinocytes were cultured for 2 or 5 days with calcium chloride to induce terminal differentiation as determined by the expression of epidermal differentiation complex genes. The cells were then stimulated with IL-4 for 3 and 24 hours, or along the 5 days culture period. We observed that IL-4 inhibits fully differentiation of keratinocytes, induces genes involved with production of inflammatory mediators, and reduces the healing capacity of human keratinocytes. Moreover, STAT6 controlled important genes involved with calcium binding, inflammation and epidermis development. Human keratinocytes were differentiated with calcium chloride for 2 days and incubated with media alone or 20ng/ml of recombinant human IL-4 for 3 and 24 hours. Human keratinocytes were differentiated with calcium chloride for 5 days with or wihout recombinant human IL-4 (20ng/ml). Keratinocytes transfected with control or STAT6 siRNA were differentiated with calcium chloride for 2 days and then stimulated with recombinant huma IL-4 for 24 hours.
Project description:Calcium and 1,25-dihydroxyvitamin D3 (1,25D3), through the actions of their respective receptors, the Ca2+-sensing receptor (CaSR) and the vitamin D receptor (VDR), potentiate keratinocyte differentiation. VDR regulates epidermal keratinocyte proliferation and differentiation by modulating gene transcription, whereas the CaSR, a member of the family C G-protein coupled receptor, calcium mobilizes intracellular calcium and induces the formation of cell-cell junctions. 1,25D3 augments the sensitivity of the prodifferentiating actions of calcium by increasing the expression of CaSR. CaSR- and VDR-deficient keratinocytes share common characteristics such as abnormal intercellular adhesion and sphigolipid metabolism. Both CaSR and VDR are abundantly expressed in epidermal stem cell populations including CD34 expressing bulge keratinocytes in hair follicles and basal cells in interfollicular epidermis. To delineate the role of CaSR- and VDR-dependent pathways in regulating epidermal development and functions in physiological state, we generated conditional CaSR-null and VDR-null mice, where Casr and VDR gene was removed from keratinocytes. Keratinocyte-specific CaSR-null and VDR-null mice manifest distinct phenotypes. CaSR-null mice display defective epidermal permeability barrier function due to aberrant keratinocyte differentiation. VDR-null mice develop alopecia after completing the first hair follicle cycling. Concurrent ablation of CaSR and VDR genes in keratinocytes delays rate of wound repair and increases incidence of skin tumor formation to a greater extent than deletion of the CaSR or VDR alone, indicative of synergistic effects of calcium and 1,25D3 signaling. Gene expression profiles and subsequent pathway analysis on the epidermis derived from 5-day-old neonates revealed that ablation of CaSR or VDR increased expression of genes associated with cancer progression and metastasis. Deletion of VDR markedly inhibited signaling pathways that regulate hair development. Furthermore, concurrent ablation of CaSR and VDR significantly suppressed calcium, VDR, Wnt/b-catenin signaling, as well as epithelial adherence junction signaling to maintain appropriate keratinocyte adhesion. These results indicated the interplay of calcium/CaSR and 1,25D3/VDR signaling in keratinocyte proliferation and differentiation, and their importance in maintaining normal epidermal adhesion and functions. n=3 CON and DKO (each sample contain RNA isolated from neonatal epidermis separated from 3 mice)
Project description:To assess if Hedgehog (Hh) responding cells in the skin have a unique expression profile, isolated keratinocytes that express the Hh response gene Gli1 were collected by FACS and their gene expression was compared to sorted CD34-expressing cells from the middle bulge region of the hair follicle and to cells from the interfollicular epidermis (IFE) by hybridization of isolated RNA to gene expression microarrays. Dissociated keratinocytes isolated form back skin of Gli1-eGFP/+ mice (2 mice pooled for each replicate) in adult telogen were sorted based on GFP expression and immunostaining for CD34. Only viable, single cells with immunostaining for α6 Integrin (to mark basal keratinocytes) were collected. GFP(+) cells were collected as the Gli1 cohort. GFP(-) CD34(+) cells were collected as the CD34 cohort, and GFP(-) CD34(-) cells were collected as interfollicular epidermis (IFE) cohort. Total RNA was extracted from each cell population and labeled for hybridization to gene expression microarrays. The experiment was preformed in triplicate, however RNA from the Gli1(+) cells in one replicate was of insufficient quality to analyze. For staining of isolated keratinocytes, cells were incubated on ice for 1 hour in SMEM containing 1%BSA and 15μL of anti-CD49f-PE antibody (BDBioscience) plus 5μL anti-CD34-APC antibody (eBioscience) for each 100μL total volume for each 2 million cells. Immediately prior to sorting, DAPI (Invitrogen) was added to the washed cells at 1μg/mL final concentration.
Project description:The p53 homologue, p63, is critical for normal epidermal development. While overexpression of deltaNp63alpha has been reported in squamous cell cancers, the contribution of p63 to cancer pathogenesis remains unclear. We previously demonstrated that overexpressed deltaNp63alpha aberrantly maintains proliferation of primary epidermal keratinocytes under conditions that normally induce growth arrest and differentiation. To identify target genes impacted by dysregulated deltaNp63alpha that may contribute to squamous cancer development and progression, microarray analyses were performed. Herein we report that elevated deltaNp63alpha differentially regulates genes in primary mouse keratinocytes involved in a variety of cellular functions, including cell cycle regulation, differentiation, skin barrier formation and function, apoptosis, host defense/inflammation, adhesion, migration and invasion. Of note, multiple protease inhibitor mRNAs were coordinately downregulated under both proliferating and differentiating culture conditions. These downregulated genes include two serine protease inhibitors: maspin (serpinB5) and plasminogen activator inhibitor-2 (PAI-2; serpinB2), as well as a tissue inhibitor of metalloproteinase-3 (TIMP-3). Correspondingly, secreted levels of TIMP-3 and PAI-2 protein declined in the presence of dysregulated deltaNp63alpha, while secreted maspin protein levels remained stable. Intracellular maspin protein expression decreased in response to overexpressed deltaNp63alpha, as did intracellular PAI-2. Unlike PAI-2 and maspin, TIMP-3 protein was not detected intracellularly in control or deltaNp63alpha-overexpressing keratinocytes, supporting a solely extracellular function for TIMP-3. Electrophoretic mobility shift assays using a p53/p63 consensus DNA binding sequence from the maspin promoter revealed binding of an endogenous transcription factor(s) to the consensus sequence in normal keratinocytes that was disrupted by overexpressed deltaNp63alpha. This binding was also interrupted by the addition of a p73 antibody, but not antibodies to p63 or p53, and was absent in samples derived from p73(-/-) keratinocytes, confirming p73 as a constituent of the endogenous transcription factor complex. These data suggest protease inhibitors as novel targets of dysregulated deltaNp63alpha in cancer pathogenesis. Keratinocytes were transduced with adenoviruses encoding deltaNp63alpha. Keratinocytes were either maintained in low calcium conditions (0.05 mM for 24 hours) (n=6) or high calcium conditions (0.12 mM for 24 hours) (n=6). Control samples consisted of keratinocytes transduced with adenoviruses encoding beta-galactosidase also treated with low calcium (n=6) and high calcium (n=6) conditions. Twelve technical repeat microarray experiments were conducted, pairing high-calcium deltaNp63alpha samples with high-calcium beta-galactosidase samples (n=6) and low-calcium deltaNp63alpha samples with low-calcium beta-galactosidase samples (n=6). Six of the technical repeats were conducted as reverse-fluoro experiments.
Project description:Long-term tissue homeostasis is governed by balanced contribution from adult stem cells. We recently identified Lrig1 as a marker of stem cells in mouse epidermis. Here, we show that Lrig1 expressing cells are molecularly and functionally distinct from previously characterized epidermal stem cell populations. During steady state homeostasis, Lrig1 expressing cells are responsible for the maintenance of the uppermost compartment of the pilosebaceous unit known as the infundibulum. Lineage tracing demonstrates that the epidermis is divided into discrete compartments during homeostasis, each maintained by its own resident stem cells. Compartment boundaries are rapidly broken when stem cell progeny are recruited to sites of injury, where they subsequently change behavior according to the environment. Oncogene activation in Lrig1 expressing cells alters proliferation but auxiliary stimuli are required for rapid tumor growth. Our data demonstrate that stem cell niches are compartmentalized according to altering requirements for tissue replenishment.
Project description:EGFR signaling controls skin development and homeostasis in mice and humans and its deficiency causes severe skin inflammation, which might affect epidermal stem cell behaviour. Here, we describe the inflammation-independent effects of EGFR-deficiency during skin morphogenesis and in adult HFSCs. Expression and alternative splicing analysis of RNAseq data from interfollicular epidermis and outer root sheath indicate that EGFR controls genes involved in epidermal differentiation, but also in centrosome function, DNA damage, cell cycle and apoptosis. Genetic experiments employing p53-deletion in EGFR–deficient epidermis reveal that EGFR signalling exhibits p53-dependent functions in proliferative epidermal compartments, as well as p53–independent functions in differentiated hair shaft keratinocytes. Loss of EGFR leads to absence of Lef1 protein specifically in the innermost epithelial hair layers, resulting in disorganization of medulla cells. Thus, our results uncover important spatial and temporal features of cell-autonomous EGFR functions in the epidermis.