DNA dioxygenases Tet2/3 regulate gene promoter accessibility and chromatin topology in lineage-specific loci to control epithelial differentiation.

Execution of lineage-specific differentiation programs requires tight coordination between many regulators including Ten-eleven translocation (TET) family enzymes, catalyzing 5-methylcytosine oxidation in DNA. Here, by using --driven ablation of genes in skin epithelial cells, we demonstrate that ablation of results in marked alterations of hair shape and length followed by hair loss. We show that, through DNA demethylation, control chromatin accessibility and Dlx3 binding and promoter activity of the and genes regulating hair shape, as well as regulate interactions between the gene promoter and distal enhancer.

Skin Aging in Long-Lived Naked Mole-Rats Is Accompanied by Increased Expression of Longevity-Associated and Tumor Suppressor Genes.

Naked mole-rats (NMRs) (Heterocephalus glaber) are long-lived mammals that possess a natural resistance to cancer and other age-related pathologies, maintaining a healthy life span >30 years. In this study, using immunohistochemical and RNA-sequencing analyses, we compare skin morphology, cellular composition, and global transcriptome signatures between young and aged (aged 3‒4 vs. 19‒23 years, respectively) NMRs.

Cryptochrome 1 is modulated by blue light in human keratinocytes and exerts positive impact on human hair growth.

Photoactivation of cryptochrome-family proteins by blue light is a well-established reaction regulating physiology of plants, fungi, bacteria, insects and birds, while impact of blue light on cryptochrome synthesis and/or activity in human non-visual cells remains unknown. Here, we show that 453 nm blue light induces cryptochrome 1 (CRY1) accumulation in human keratinocytes and the hair follicle. CRY1 is prominently expressed in the human anagen hair follicle, including epithelial stem cells.

Method to Study Skin Cancer: Two-Stage Chemically Induced Carcinogenesis in Mouse Skin.

Two-stage chemical carcinogenesis method is widely used to elucidate genetic and molecular changes that lead to skin cancer development, as well as to test chemotherapeutic properties of novel drugs. This protocol allows researchers to reliably induce benign papilloma development and their conversion to squamous cell carcinoma in the skin of susceptible mouse strains in response to a single dose of carcinogen 2,4-dimethoxybenzaldehyde (DMBA) and repetitive applications of tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA).

3D-FISH Analysis of the Spatial Genome Organization in Skin Cells in Situ.

Spatial genome organization in the cell nucleus plays a crucial role in the control of genome functions. Our knowledge about spatial genome organization is relying on the advances in gene imaging technologies and the biochemical approaches based on the spatial dependent ligation of the genomic regions. Fluorescent in situ hybridization using specific fluorescent DNA and RNA probes in cells and tissues with the spatially preserved nuclear and genome architecture (3D-FISH) provides a powerful tool for the further advancement of our knowledge about genome structure and functions.

5C analysis of the Epidermal Differentiation Complex locus reveals distinct chromatin interaction networks between gene-rich and gene-poor TADs in skin epithelial cells.

Mammalian genomes contain several dozens of large (>0.5 Mbp) lineage-specific gene loci harbouring functionally related genes. However, spatial chromatin folding, organization of the enhancer-promoter networks and their relevance to Topologically Associating Domains (TADs) in these loci remain poorly understood.

Exploring a Role for Regulatory miRNAs In Wound Healing during Ageing:Involvement of miR-200c in wound repair.

Multiple factors and conditions can lead to impaired wound healing. Chronic non-healing wounds are a common problem among the elderly. To identify microRNAs negatively impacting the wound repair, global miRNA profiling of wounds collected from young and old mice was performed.

A new path in defining light parameters for hair growth: Discovery and modulation of photoreceptors in human hair follicle.

Background And Objective: Though devices for hair growth based on low levels of light have shown encouraging results, further improvements of their efficacy is impeded by a lack of knowledge on the exact molecular targets that mediate physiological response in skin and hair follicle. The aim of this study was to investigate the expression of selected light-sensitive receptors in the human hair follicle and to study the impact of UV-free blue light on hair growth ex vivo.

Material And Methods: The expression of Opsin receptors in human skin and hair follicles has been characterized using RT-qPCR and immunofluorescence approaches.

Repressing the Keratinocyte Genome: How the Polycomb Complex Subunits Operate in Concert to Control Skin and Hair Follicle Development.

The Polycomb group proteins are transcriptional repressors that are critically important in the control of stem cell activity and maintenance of the identity of differentiated cells. Polycomb proteins interact with each other to form chromatin-associated repressive complexes (Polycomb repressive complexes 1 and 2) leading to chromatin compaction and gene silencing. However, the roles of the distinct components of the Polycomb repressive complex 2 in the control of skin development and keratinocyte differentiation remain obscure.

Cbx4 maintains the epithelial lineage identity and cell proliferation in the developing stratified epithelium.

During development, multipotent progenitor cells establish lineage-specific programmers of gene activation and silencing underlying their differentiation into specialized cell types. We show that the Polycomb component Cbx4 serves as a critical determinant that maintains the epithelial identity in the developing epidermis by repressing nonepidermal gene expression programs. Cbx4 ablation in mice results in a marked decrease of the epidermal thickness and keratinocyte (KC) proliferation associated with activation of numerous neuronal genes and genes encoding cyclin-dependent kinase inhibitors (p16/p19 and p57).

MicroRNA-214 controls skin and hair follicle development by modulating the activity of the Wnt pathway.

Skin development is governed by complex programs of gene activation and silencing, including microRNA-dependent modulation of gene expression. Here, we show that miR-214 regulates skin morphogenesis and hair follicle (HF) cycling by targeting β-catenin, a key component of the Wnt signaling pathway. miR-214 exhibits differential expression patterns in the skin epithelium, and its inducible overexpression in keratinocytes inhibited proliferation, which resulted in formation of fewer HFs with decreased hair bulb size and thinner hair production.

The Epigenetic Regulation of Wound Healing.

Epigenetic regulatory mechanisms are essential for epidermal homeostasis and contribute to the pathogenesis of many skin diseases, including skin cancer and psoriasis. However, while the epigenetic regulation of epidermal homeostasis is now becoming active area of research, the epigenetic mechanisms controlling the wound healing response remain relatively untouched. Substantial progress achieved within the last two decades in understanding epigenetic mechanisms controlling gene expression allowed defining several levels, including covalent DNA and histone modifications, ATP-dependent and higher-order chromatin chromatin remodeling, as well as noncoding RNA- and microRNA-dependent regulation.

p63 and Brg1 control developmentally regulated higher-order chromatin remodelling at the epidermal differentiation complex locus in epidermal progenitor cells.

Chromatin structural states and their remodelling, including higher-order chromatin folding and three-dimensional (3D) genome organisation, play an important role in the control of gene expression. The role of 3D genome organisation in the control and execution of lineage-specific transcription programmes during the development and differentiation of multipotent stem cells into specialised cell types remains poorly understood. Here, we show that substantial remodelling of the higher-order chromatin structure of the epidermal differentiation complex (EDC), a keratinocyte lineage-specific gene locus on mouse chromosome 3, occurs during epidermal morphogenesis.

Bone morphogenetic protein signaling suppresses wound-induced skin repair by inhibiting keratinocyte proliferation and migration.

Bone morphogenetic protein (BMP) signaling plays a key role in the control of skin development and postnatal remodeling by regulating keratinocyte proliferation, differentiation, and apoptosis. To study the role of BMPs in wound-induced epidermal repair, we used transgenic mice overexpressing the BMP downstream component Smad1 under the control of a K14 promoter as an in vivo model, as well as ex vivo and in vitro assays. K14-caSmad1 (transgenic mice overexpressing a constitutively active form of Smad1 under K14 promoter) mice exhibited retarded wound healing associated with significant inhibition of proliferation and increased apoptosis in healing wound epithelium.

Remodeling of three-dimensional organization of the nucleus during terminal keratinocyte differentiation in the epidermis.

The nucleus of epidermal keratinocytes (KCs) is a complex and highly compartmentalized organelle, whose structure is markedly changed during terminal differentiation and transition of the genome from a transcriptionally active state seen in the basal and spinous epidermal cells to a fully inactive state in the keratinized cells of the cornified layer. Here, using multicolor confocal microscopy, followed by computational image analysis and mathematical modeling, we demonstrate that in normal mouse footpad epidermis, transition of KCs from basal epidermal layer to the granular layer is accompanied by marked differences in nuclear architecture and microenvironment including the following: (i) decrease in the nuclear volume; (ii) decrease in expression of the markers of transcriptionally active chromatin; (iii) internalization and decrease in the number of nucleoli; (iv) increase in the number of pericentromeric heterochromatic clusters; and (v) increase in the frequency of associations between the pericentromeric clusters, chromosomal territory 3, and nucleoli. These data suggest a role for nucleoli and pericentromeric heterochromatin clusters as organizers of nuclear microenvironment required for proper execution of gene expression programs in differentiating KCs, and provide important background information for further analyses of alterations in the topological genome organization seen in pathological skin conditions, including disorders of epidermal differentiation and epidermal tumors.

Cbx4 regulates the proliferation of thymic epithelial cells and thymus function.

Thymic epithelial cells (TECs) are the main component of the thymic stroma, which supports T-cell proliferation and repertoire selection. Here, we demonstrate that Cbx4, a Polycomb protein that is highly expressed in the thymic epithelium, has an essential and non-redundant role in thymic organogenesis. Targeted disruption of Cbx4 causes severe hypoplasia of the fetal thymus as a result of reduced thymocyte proliferation.

Epigenetic regulation of gene expression in keratinocytes.

The nucleus is a complex and highly compartmentalized organelle, which undergoes major organization changes during cell differentiation, allowing cells to become specialized and fulfill their functions. During terminal differentiation of the epidermal keratinocytes, the nucleus undergoes a programmed transformation from active status, associated with execution of the genetic programs of cornification and epidermal barrier formation, to a fully inactive condition and becomes a part of the keratinized cells of the cornified layer. Tremendous progress achieved within the past two decades in understanding the biology of the nucleus and epigenetic mechanisms controlling gene expression allowed defining several levels in the regulation of cell differentiation-associated gene expression programs, including an accessibility of the gene regulatory regions to DNA-protein interactions, covalent DNA and histone modifications, and ATP-dependent chromatin remodeling, as well as higher-order chromatin remodeling and nuclear compartmentalization of the genes and transcription machinery.

Lhx2 differentially regulates Sox9, Tcf4 and Lgr5 in hair follicle stem cells to promote epidermal regeneration after injury.

The Lhx2 transcription factor plays essential roles in morphogenesis and patterning of ectodermal derivatives as well as in controlling stem cell activity. Here, we show that during murine skin morphogenesis, Lhx2 is expressed in the hair follicle (HF) buds, whereas in postnatal telogen HFs Lhx2(+) cells reside in the stem cell-enriched epithelial compartments (bulge, secondary hair germ) and co-express selected stem cell markers (Sox9, Tcf4 and Lgr5). Remarkably, Lhx2(+) cells represent the vast majority of cells in the bulge and secondary hair germ that proliferate in response to skin injury.

MicroRNA-21 is an important downstream component of BMP signalling in epidermal keratinocytes.

Bone morphogenetic proteins (BMPs) play essential roles in the control of skin development, postnatal tissue remodelling and tumorigenesis. To explore whether some of the effects of BMP signalling are mediated by microRNAs, we performed genome-wide microRNA (miRNA) screening in primary mouse keratinocytes after BMP4 treatment. Microarray analysis revealed substantial BMP4-dependent changes in the expression of distinct miRNAs, including miR-21.

p63 regulates Satb1 to control tissue-specific chromatin remodeling during development of the epidermis.

During development, multipotent progenitor cells establish tissue-specific programs of gene expression. In this paper, we show that p63 transcription factor, a master regulator of epidermal morphogenesis, executes its function in part by directly regulating expression of the genome organizer Satb1 in progenitor cells. p63 binds to a proximal regulatory region of the Satb1 gene, and p63 ablation results in marked reduction in the Satb1 expression levels in the epidermis.

Micro-RNA-31 controls hair cycle-associated changes in gene expression programs of the skin and hair follicle.

The hair follicle is a cyclic biological system that progresses through stages of growth, regression, and quiescence, which involves dynamic changes in a program of gene regulation. Micro-RNAs (miRNAs) are critically important for the control of gene expression and silencing. Here, we show that global miRNA expression in the skin markedly changes during distinct stages of the hair cycle in mice.

BMP signaling induces cell-type-specific changes in gene expression programs of human keratinocytes and fibroblasts.

BMP signaling has a crucial role in skin development and homeostasis, whereas molecular mechanisms underlying its involvement in regulating gene expression programs in keratinocytes and fibroblasts remain largely unknown. We show here that several BMP ligands, all BMP receptors, and BMP-associated Smad1/5/8 are expressed in human primary epidermal keratinocytes and dermal fibroblasts. Treatment of both cell types by BMP-4 resulted in the activation of the BMP-Smad, but not BMP-MAPK pathways.

Bone morphogenetic protein antagonist noggin promotes skin tumorigenesis via stimulation of the Wnt and Shh signaling pathways.

Bone morphogenetic proteins (BMPs) play pivotal roles in the regulation of skin development. To study the role of BMPs in skin tumorigenesis, BMP antagonist noggin was used to generate keratin 14-targeted transgenic mice. In contrast to wild-type mice, transgenic mice developed spontaneous hair follicle-derived tumors, which resemble human trichofolliculoma.