1
|
Abstract
The epidermis is a specialized epithelium that constitutes the outermost layer of the skin, and it provides a protective barrier against environmental assaults. Primarily consisting of multilayered keratinocytes, the epidermis is continuously renewed by proliferation of stem cells and the differentiation of their progeny, which undergo terminal differentiation as they leave the basal layer and move upward toward the surface, where they die and slough off. Basal keratinocytes rest on a basement membrane at the dermal-epidermal junction that is composed of specific extracellular matrix proteins organized into interactive and mechanically supportive networks. Firm attachment of basal keratinocytes, and their dynamic regulation via focal adhesions and hemidesmosomes, is essential for maintaining major skin processes, such as self-renewal, barrier function, and resistance to physical and chemical stresses. The adhesive integrin receptors expressed by epidermal cells serve structural, signaling, and mechanosensory roles that are critical for epidermal cell anchorage and tissue homeostasis. More specifically, the basement membrane components play key roles in preserving the stem cell pool, and establishing cell polarity cues enabling asymmetric cell divisions, which result in the transition from a proliferative basal cell layer to suprabasal cells committed to terminal differentiation. Finally, through a well-regulated sequence of synthesis and remodeling, the components of the dermal-epidermal junction play an essential role in regeneration of the epidermis during skin healing. Here too, they provide biological and mechanical signals that are essential to the restoration of barrier function.
Collapse
Affiliation(s)
- Patricia Rousselle
- Laboratoire de Biologie Tissulaire et Ingénierie Thérapeutique, UMR 5305, CNRS, Université Lyon 1, Lyon, France
| | - Chloé Laigle
- Laboratoire de Biologie Tissulaire et Ingénierie Thérapeutique, UMR 5305, CNRS, Université Lyon 1, Lyon, France
| | - Gaelle Rousselet
- Laboratoire de Biologie Tissulaire et Ingénierie Thérapeutique, UMR 5305, CNRS, Université Lyon 1, Lyon, France
| |
Collapse
|
2
|
Baess SC, Burkhart AK, Cappello S, Graband A, Seré K, Zenke M, Niemann C, Iden S. Lrig1- and Wnt-dependent niches dictate segregation of resident immune cells and melanocytes in murine tail epidermis. Development 2022; 149:275959. [PMID: 35815643 PMCID: PMC9382897 DOI: 10.1242/dev.200154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 06/13/2022] [Indexed: 11/20/2022]
Abstract
The barrier-forming, self-renewing mammalian epidermis comprises keratinocytes, pigment-producing melanocytes and resident immune cells as first-line host defense. In murine tail skin, interfollicular epidermis patterns into pigmented ‘scale’ and hypopigmented ‘interscale’ epidermis. Why and how mature melanocytes accumulate in scale epidermis is unresolved. Here, we delineate a cellular hierarchy among epidermal cell types that determines skin patterning. Already during postnatal development, melanocytes co-segregate with newly forming scale compartments. Intriguingly, this process coincides with partitioning of both Langerhans cells and dendritic epidermal T cells to interscale epidermis, suggesting functional segregation of pigmentation and immune surveillance. Analysis of non-pigmented mice and of mice lacking melanocytes or resident immune cells revealed that immunocyte patterning is melanocyte and melanin independent and, vice versa, immune cells do not control melanocyte localization. Instead, genetically enforced progressive scale fusion upon Lrig1 deletion showed that melanocytes and immune cells dynamically follow epithelial scale:interscale patterns. Importantly, disrupting Wnt-Lef1 function in keratinocytes caused melanocyte mislocalization to interscale epidermis, implicating canonical Wnt signaling in organizing the pigmentation pattern. Together, this work uncovers cellular and molecular principles underlying the compartmentalization of tissue functions in skin. Summary: Pigmentation and immune surveillance functions in murine tail skin are spatially segregated by Lrig1- and Wnt-Lef1-dependent keratinocyte lineages that control the partitioning of melanocytes and tissue-resident immune cells into distinct epidermal niches.
Collapse
Affiliation(s)
- Susanne C. Baess
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne 1 , 50931 Cologne , Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne 2 , 50931 Cologne , Germany
- Cell and Developmental Biology, Center of Human and Molecular Biology (ZHMB), Saarland University 3 , Faculty of Medicine, 66421 Homburg/Saar , Germany
| | - Ann-Kathrin Burkhart
- Cell and Developmental Biology, Center of Human and Molecular Biology (ZHMB), Saarland University 3 , Faculty of Medicine, 66421 Homburg/Saar , Germany
| | - Sabrina Cappello
- Cell and Developmental Biology, Center of Human and Molecular Biology (ZHMB), Saarland University 3 , Faculty of Medicine, 66421 Homburg/Saar , Germany
| | - Annika Graband
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne 1 , 50931 Cologne , Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne 2 , 50931 Cologne , Germany
- Cell and Developmental Biology, Center of Human and Molecular Biology (ZHMB), Saarland University 3 , Faculty of Medicine, 66421 Homburg/Saar , Germany
| | - Kristin Seré
- Institute for Biomedical Engineering 4 , Department of Cell Biology , , 52074 Aachen , Germany
- RWTH Aachen University Medical School 4 , Department of Cell Biology , , 52074 Aachen , Germany
- Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University 5 , 52074 Aachen , Germany
| | - Martin Zenke
- Institute for Biomedical Engineering 4 , Department of Cell Biology , , 52074 Aachen , Germany
- RWTH Aachen University Medical School 4 , Department of Cell Biology , , 52074 Aachen , Germany
- Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University 5 , 52074 Aachen , Germany
| | - Catherin Niemann
- Center for Molecular Medicine Cologne (CMMC), University of Cologne 2 , 50931 Cologne , Germany
- Center of Biochemistry 6 , Faculty of Medicine , , 50931 Cologne , Germany
- University Hospital Cologne 6 , Faculty of Medicine , , 50931 Cologne , Germany
| | - Sandra Iden
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne 1 , 50931 Cologne , Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne 2 , 50931 Cologne , Germany
- Cell and Developmental Biology, Center of Human and Molecular Biology (ZHMB), Saarland University 3 , Faculty of Medicine, 66421 Homburg/Saar , Germany
| |
Collapse
|
3
|
Wang J, Eming SA, Ding X. Role of mTOR Signaling Cascade in Epidermal Morphogenesis and Skin Barrier Formation. Biology 2022; 11:biology11060931. [PMID: 35741452 PMCID: PMC9220260 DOI: 10.3390/biology11060931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 06/13/2022] [Accepted: 06/17/2022] [Indexed: 11/16/2022]
Abstract
Simple Summary The skin epidermis is a stratified multilayered epithelium that provides a life-sustaining protective and defensive barrier for our body. The barrier machinery is established and maintained through a tightly regulated keratinocyte differentiation program. Under normal conditions, the basal layer keratinocytes undergo active proliferation and migration upward, differentiating into the suprabasal layer cells. Perturbation of the epidermal differentiation program often results in skin barrier defects and inflammatory skin disorders. The protein kinase mechanistic target of rapamycin (mTOR) is the central hub of cell growth, metabolism and nutrient signaling. Over the past several years, we and others using transgenic mouse models have unraveled that mTOR signaling is critical for epidermal differentiation and barrier formation. On the other hand, there is increasing evidence that disturbed activation of mTOR signaling is significantly implicated in the development of various skin diseases. In this review, we focus on the formation of skin barrier and discuss the current understanding on how mTOR signaling networks, including upstream inputs, kinases and downstream effectors, regulate epidermal differentiation and skin barrier formation. We hope this review will help us better understand the metabolic signaling in the epidermis, which may open new vistas for epidermal barrier defect-associated disease therapy. Abstract The skin epidermis, with its capacity for lifelong self-renewal and rapid repairing response upon injury, must maintain an active status in metabolism. Mechanistic target of rapamycin (mTOR) signaling is a central controller of cellular growth and metabolism that coordinates diverse physiological and pathological processes in a variety of tissues and organs. Recent evidence with genetic mouse models highlights an essential role of the mTOR signaling network in epidermal morphogenesis and barrier formation. In this review, we focus on the recent advances in understanding how mTOR signaling networks, including upstream inputs, kinases and downstream effectors, regulate epidermal morphogenesis and skin barrier formation. Understanding the details of the metabolic signaling will be critical for the development of novel pharmacological approaches to promote skin barrier regeneration and to treat epidermal barrier defect-associated diseases.
Collapse
Affiliation(s)
- Juan Wang
- Institute of Geriatrics (Shanghai University), Affiliated Nantong Hospital of Shanghai University (The Sixth People’s Hospital of Nantong), School of Medicine, Shanghai University, Nantong 226011, China;
- Shanghai Engineering Research Center of Organ Repair, School of Medicine, Shanghai University, Shanghai 200444, China
| | - Sabine A. Eming
- Department of Dermatology, University of Cologne, 50937 Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50674 Cologne, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, 50931 Cologne, Germany
- Institute of Zoology, Developmental Biology Unit, University of Cologne, 50674 Cologne, Germany
- Correspondence: (S.A.E.); (X.D.); Tel.: +86-137-6457-1130 (X.D.)
| | - Xiaolei Ding
- Institute of Geriatrics (Shanghai University), Affiliated Nantong Hospital of Shanghai University (The Sixth People’s Hospital of Nantong), School of Medicine, Shanghai University, Nantong 226011, China;
- Shanghai Engineering Research Center of Organ Repair, School of Medicine, Shanghai University, Shanghai 200444, China
- Department of Dermatology, University of Cologne, 50937 Cologne, Germany
- Correspondence: (S.A.E.); (X.D.); Tel.: +86-137-6457-1130 (X.D.)
| |
Collapse
|
4
|
Abstract
Cells are biochemically and morphologically polarized, which allows them to produce different cell shapes for various functions. Remarkably, some polarity protein complexes are asymmetrically recruited and concentrated on limited membrane regions, which is essential for the establishment and maintenance of diverse cell polarity. Though the components and mutual interactions within these protein complexes have been extensively investigated, how these proteins autonomously concentrate at local membranes and whether they have the same organization mechanism in the condensed assembly as that in aqueous solution remain elusive. A number of recent studies suggest that these highly concentrated polarity protein assemblies are membraneless biomolecular condensates which form through liquid-liquid phase separation (LLPS) of specific proteins. In this perspective, we summarize the LLPS-driven condensed protein assemblies found in asymmetric cell division, epithelial cell polarity, and neuronal synapse formation and function. These findings suggest that LLPS may be a general strategy for cells to achieve local condensation of specific proteins, thus establishing cell polarity.
Collapse
Affiliation(s)
- Heyang Wei
- Department of Neurosurgery, Huashan Hospital, the Shanghai Key Laboratory of Medical Epigenetics, Institutes of Biomedical Sciences, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Wenyu Wen
- Department of Neurosurgery, Huashan Hospital, the Shanghai Key Laboratory of Medical Epigenetics, Institutes of Biomedical Sciences, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| |
Collapse
|
5
|
Dias Gomes M, Iden S. Orchestration of tissue-scale mechanics and fate decisions by polarity signalling. EMBO J 2021; 40:e106787. [PMID: 33998017 PMCID: PMC8204866 DOI: 10.15252/embj.2020106787] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 03/10/2021] [Accepted: 03/12/2021] [Indexed: 02/06/2023] Open
Abstract
Eukaryotic development relies on dynamic cell shape changes and segregation of fate determinants to achieve coordinated compartmentalization at larger scale. Studies in invertebrates have identified polarity programmes essential for morphogenesis; however, less is known about their contribution to adult tissue maintenance. While polarity‐dependent fate decisions in mammals utilize molecular machineries similar to invertebrates, the hierarchies and effectors can differ widely. Recent studies in epithelial systems disclosed an intriguing interplay of polarity proteins, adhesion molecules and mechanochemical pathways in tissue organization. Based on major advances in biophysics, genome editing, high‐resolution imaging and mathematical modelling, the cell polarity field has evolved to a remarkably multidisciplinary ground. Here, we review emerging concepts how polarity and cell fate are coupled, with emphasis on tissue‐scale mechanisms, mechanobiology and mammalian models. Recent findings on the role of polarity signalling for tissue mechanics, micro‐environmental functions and fate choices in health and disease will be summarized.
Collapse
Affiliation(s)
- Martim Dias Gomes
- CECAD Cluster of Excellence, University of Cologne, Cologne, Germany.,Cell and Developmental Biology, Faculty of Medicine, Center of Human and Molecular Biology (ZHMB), Saarland University, Homburg, Germany
| | - Sandra Iden
- CECAD Cluster of Excellence, University of Cologne, Cologne, Germany.,Cell and Developmental Biology, Faculty of Medicine, Center of Human and Molecular Biology (ZHMB), Saarland University, Homburg, Germany.,CMMC, University of Cologne, Cologne, Germany
| |
Collapse
|