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Cuevas-Diaz Duran R, Martinez-Ledesma E, Garcia-Garcia M, Bajo Gauzin D, Sarro-Ramírez A, Gonzalez-Carrillo C, Rodríguez-Sardin D, Fuentes A, Cardenas-Lopez A. The Biology and Genomics of Human Hair Follicles: A Focus on Androgenetic Alopecia. Int J Mol Sci 2024; 25:2542. [PMID: 38473791 DOI: 10.3390/ijms25052542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 02/16/2024] [Accepted: 02/18/2024] [Indexed: 03/14/2024] Open
Abstract
Androgenetic alopecia is a highly prevalent condition mainly affecting men. This complex trait is related to aging and genetics; however, multiple other factors, for example, lifestyle, are also involved. Despite its prevalence, the underlying biology of androgenetic alopecia remains elusive, and thus advances in its treatment have been hindered. Herein, we review the functional anatomy of hair follicles and the cell signaling events that play a role in follicle cycling. We also discuss the pathology of androgenetic alopecia and the known molecular mechanisms underlying this condition. Additionally, we describe studies comparing the transcriptional differences in hair follicles between balding and non-balding scalp regions. Given the genetic contribution, we also discuss the most significant risk variants found to be associated with androgenetic alopecia. A more comprehensive understanding of this pathology may be generated through using multi-omics approaches.
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Affiliation(s)
- Raquel Cuevas-Diaz Duran
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey 64710, NL, Mexico
- CapilarFix®, Monterrey 66220, NL, Mexico
| | - Emmanuel Martinez-Ledesma
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey 64710, NL, Mexico
- Tecnologico de Monterrey, Institute for Obesity Research, Monterrey 64849, NL, Mexico
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Heidary H, Mardi A, Mousavi SM, Khazaie G, Golab F. Hairless Gene Nonsense Mutations in Alopecia Universalis: A Case Report. Iran J Public Health 2021; 50:1275-1279. [PMID: 34540749 PMCID: PMC8410955 DOI: 10.18502/ijph.v50i6.6429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 02/14/2021] [Indexed: 11/24/2022]
Abstract
Alopecia universalis (AU) congenital, known as generalized atrichia, is a severe form of autosomal recessive alopecia that results in complete hair loss of scalp and body. Mutations in the human hairless gene (HR) are associated with the phenotype of the disease. A consanguineous couple who had a child with the generalized atrichia sign referred to us for genetic counseling. According to the patient’s symptoms and after thorough examination and history taking, the HR gene was the candidate gene to be assessed and analyzed. For this purpose targeted primers were designed for all exons of the HR gene followed by running PCR for exons amplification. Finally, the PCR products were sequenced. Whole-gene sequence analysis revealed a nonsense homozygous mutation in exon 6 that, according to the ACMG guide, is a pathogenic variant. Sequence analysis of the exon in parents reveals that they are heterozygout for the non-sense mutation, as well.
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Affiliation(s)
- Hamed Heidary
- Department of Medical Genetics, Ali Asghar Hospital, Iran University of Medical Sciences, Tehran, Iran
| | - Ali Mardi
- Department of Medical Genetics, Ali Asghar Hospital, Iran University of Medical Sciences, Tehran, Iran
| | - Seyyed Mohammad Mousavi
- Department of Medical Genetics, Ali Asghar Hospital, Iran University of Medical Sciences, Tehran, Iran
| | - Ghasem Khazaie
- Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Fereshteh Golab
- Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran
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Ji S, Zhu Z, Sun X, Fu X. Functional hair follicle regeneration: an updated review. Signal Transduct Target Ther 2021; 6:66. [PMID: 33594043 PMCID: PMC7886855 DOI: 10.1038/s41392-020-00441-y] [Citation(s) in RCA: 71] [Impact Index Per Article: 23.7] [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: 06/15/2020] [Revised: 09/25/2020] [Accepted: 11/03/2020] [Indexed: 01/31/2023] Open
Abstract
The hair follicle (HF) is a highly conserved sensory organ associated with the immune response against pathogens, thermoregulation, sebum production, angiogenesis, neurogenesis and wound healing. Although recent advances in lineage-tracing techniques and the ability to profile gene expression in small populations of cells have increased the understanding of how stem cells operate during hair growth and regeneration, the construction of functional follicles with cycling activity is still a great challenge for the hair research field and for translational and clinical applications. Given that hair formation and cycling rely on tightly coordinated epithelial-mesenchymal interactions, we thus review potential cell sources with HF-inducive capacities and summarize current bioengineering strategies for HF regeneration with functional restoration.
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Affiliation(s)
- Shuaifei Ji
- grid.506261.60000 0001 0706 7839Research Center for Tissue Repair and Regeneration affiliated to the Medical Innovation Research Department and 4th Medical Center, PLA General Hospital and PLA Medical College; PLA Key Laboratory of Tissue Repair and Regenerative Medicine and Beijing Key Research Laboratory of Skin Injury, Repair and Regeneration; Research Unit of Trauma Care, Tissue Repair and Regeneration, Chinese Academy of Medical Sciences, 2019RU051, Beijing, 100048 People’s Republic of China
| | - Ziying Zhu
- grid.506261.60000 0001 0706 7839Research Center for Tissue Repair and Regeneration affiliated to the Medical Innovation Research Department and 4th Medical Center, PLA General Hospital and PLA Medical College; PLA Key Laboratory of Tissue Repair and Regenerative Medicine and Beijing Key Research Laboratory of Skin Injury, Repair and Regeneration; Research Unit of Trauma Care, Tissue Repair and Regeneration, Chinese Academy of Medical Sciences, 2019RU051, Beijing, 100048 People’s Republic of China
| | - Xiaoyan Sun
- grid.506261.60000 0001 0706 7839Research Center for Tissue Repair and Regeneration affiliated to the Medical Innovation Research Department and 4th Medical Center, PLA General Hospital and PLA Medical College; PLA Key Laboratory of Tissue Repair and Regenerative Medicine and Beijing Key Research Laboratory of Skin Injury, Repair and Regeneration; Research Unit of Trauma Care, Tissue Repair and Regeneration, Chinese Academy of Medical Sciences, 2019RU051, Beijing, 100048 People’s Republic of China
| | - Xiaobing Fu
- grid.506261.60000 0001 0706 7839Research Center for Tissue Repair and Regeneration affiliated to the Medical Innovation Research Department and 4th Medical Center, PLA General Hospital and PLA Medical College; PLA Key Laboratory of Tissue Repair and Regenerative Medicine and Beijing Key Research Laboratory of Skin Injury, Repair and Regeneration; Research Unit of Trauma Care, Tissue Repair and Regeneration, Chinese Academy of Medical Sciences, 2019RU051, Beijing, 100048 People’s Republic of China
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Swanson JB, Vagnozzi AN, Veniaminova NA, Wong SY. Loss of Gata6 causes dilation of the hair follicle canal and sebaceous duct. Exp Dermatol 2018; 28:345-349. [PMID: 30033638 DOI: 10.1111/exd.13757] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 07/20/2018] [Indexed: 12/17/2022]
Abstract
The uppermost aspect of the hair follicle, known as the infundibulum or hair canal, provides a passageway for hair shaft egress and sebum secretion. Recent studies have indicated that the infundibulum and sebaceous ducts are lined by molecularly distinct differentiated cells expressing markers including Keratin 79 and Gata6. Here, we ablated Gata6 from the skin and observed dilation of both the hair canal and sebaceous ducts, independent of gender and hair cycle stage. Constitutive loss of Gata6 yielded only a mild delay in depilation-induced entry into anagen, while unperturbed mutant mice possessed overtly normal skin and hair. Furthermore, we noted that Keratin 79 and Gata6 expression and localization did not depend upon each other. Our findings implicate Gata6 in maintaining the upper hair follicle and suggest that regulation of this transcription factor may be compromised in pathologies such as acne or infundibular cystic diseases that are characterized by abnormal expansion of this follicular domain.
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Affiliation(s)
- Jacob B Swanson
- Departments of Dermatology and Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Alicia N Vagnozzi
- Departments of Dermatology and Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Natalia A Veniaminova
- Departments of Dermatology and Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Sunny Y Wong
- Departments of Dermatology and Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
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Abstract
Dermal white adipose tissue (dWAT) is increasingly appreciated as a special fat depot. The adipocytes in this depot exert a variety of unique effects on their surrounding cells and can undergo massive phenotypic changes. Significant modulation of dWAT content can be observed both in intrinsically and extrinsically aged skin. Specifically, skin that has been chronically photo-damaged displays a reduction of the dWAT volume, caused by the replacement of adipocytes by fibrotic structures. This is likely to be caused by the recently uncovered process described as "adipocyte-myofibroblast transition" (AMT). In addition, contributions of dermal adipocytes to the skin aging processes are also indirectly supported by spatial correlations between the prevalence of hypertrophic scarring and the appearance of signs of skin aging in different ethnic groups. These observations could elevate dermal adipocytes to prime targets in strategies aimed at counteracting skin aging.
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Affiliation(s)
| | - Philipp E. Scherer
- Touchstone Diabetes Center, Departments of Internal Medicine and Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Calliess T, Bartsch I, Haupt M, Reebmann M, Schwarze M, Stiesch M, Pfaffenroth C, Sluszniak M, Dempwolf W, Menzel H, Witte F, Willbold E. In vivo comparative study of tissue reaction to bare and antimicrobial polymer coated transcutaneous implants. Materials Science and Engineering: C 2016; 61:712-9. [DOI: 10.1016/j.msec.2015.12.095] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 12/03/2015] [Accepted: 12/31/2015] [Indexed: 10/22/2022]
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Yamaki K, Yoshino S. A new, rapid in vivo method to evaluate allergic responses through distinctive distribution of a fluorescent-labeled immune complex: Potential to investigate anti-allergic effects of compounds administered either systemically or topically to the skin. J Immunol Methods 2016; 428:58-68. [DOI: 10.1016/j.jim.2015.11.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 11/06/2015] [Accepted: 11/23/2015] [Indexed: 02/02/2023]
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Schneider MR, Paus R. Deciphering the functions of the hair follicle infundibulum in skin physiology and disease. Cell Tissue Res 2014; 358:697-704. [DOI: 10.1007/s00441-014-1999-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 09/04/2014] [Indexed: 12/22/2022]
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Fujimoto S, Takase T, Kadono N, Maekubo K, Hirai Y. Krtap11-1, a hair keratin-associated protein, as a possible crucial element for the physical properties of hair shafts. J Dermatol Sci 2013; 74:39-47. [PMID: 24439038 DOI: 10.1016/j.jdermsci.2013.12.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/17/2013] [Accepted: 12/18/2013] [Indexed: 12/11/2022]
Abstract
BACKGROUND The physical properties of the hair are predominantly determined by the assembly of keratin bundles. The keratin-associated proteins (Krtaps) are thought to be involved in keratin bundle assembly, however, the functional role of the individual member still remains largely unknown. OBJECTIVE The aim of this study is to clarify the role of a unique class of Krtaps, Krtap11-1, in the development and physical properties of the hair. METHODS The expression regulation of Krtap11-1 was analyzed and its binding partners in the hair cortex were determined. Also, the effects of the forcible expression of this protein on the hair follicle development were analyzed in culture. RESULTS The expression pattern of Krtap11-1 was concentrically asymmetric in the faulty hair that develops in Foxn1nu mice. In cultured keratinocytes, the expression of Krtap11-1 transgene product was strictly regulated by the keratinization process and proteasome-dependent protein elimination. While the association with keratin as well as the cohesive self-assembly of Krtap11-1 appeared to be stabilized by disulfide cross-links, the biotinylated Krtap11-1 probe enabled the adherence to certain type I keratins in the hair cortex, including K31, 33 and 34, in the absence of disulfide formation. When embryonic upper lip rudiments were forcibly introduced with Krtap11-1, the hair follicles formed irregularly arranged globular hair keratin-clumps surrounded by multilayered epithelial cells in culture. CONCLUSION Krtap11-1 may play an important role on keratin-bundle assembly in the hair cortex and this study provides insight into the physical properties of the hair shaft.
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Affiliation(s)
- Shunsuke Fujimoto
- Department of Bioscience, Graduate School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda 669-1337, Japan
| | - Takahisa Takase
- Department of Bioscience, Graduate School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda 669-1337, Japan
| | - Nanako Kadono
- Department of Bioscience, Graduate School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda 669-1337, Japan
| | - Kenji Maekubo
- Department of Bioscience, Graduate School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda 669-1337, Japan
| | - Yohei Hirai
- Department of Bioscience, Graduate School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda 669-1337, Japan.
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Chen Z, Wang Z, Xu S, Zhou K, Yang G. Characterization of hairless (Hr) and FGF5 genes provides insights into the molecular basis of hair loss in cetaceans. BMC Evol Biol 2013; 13:34. [PMID: 23394579 PMCID: PMC3608953 DOI: 10.1186/1471-2148-13-34] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Accepted: 01/30/2013] [Indexed: 11/29/2022] Open
Abstract
Background Hair is one of the main distinguishing characteristics of mammals and it has many important biological functions. Cetaceans originated from terrestrial mammals and they have evolved a series of adaptations to aquatic environments, which are of evolutionary significance. However, the molecular mechanisms underlying their aquatic adaptations have not been well explored. This study provided insights into the evolution of hair loss during the transition from land to water by investigating and comparing two essential regulators of hair follicle development and hair follicle cycling, i.e., the Hairless (Hr) and FGF5 genes, in representative cetaceans and their terrestrial relatives. Results The full open reading frame sequences of the Hr and FGF5 genes were characterized in seven cetaceans. The sequence characteristics and evolutionary analyses suggested the functional loss of the Hr gene in cetaceans, which supports the loss of hair during their full adaptation to aquatic habitats. By contrast, positive selection for the FGF5 gene was found in cetaceans where a series of positively selected amino acid residues were identified. Conclusions This is the first study to investigate the molecular basis of the hair loss in cetaceans. Our investigation of Hr and FGF5, two indispensable regulators of the hair cycle, provide some new insights into the molecular basis of hair loss in cetaceans. The results suggest that positive selection for the FGF5 gene might have promoted the termination of hair growth and early entry into the catagen stage of hair follicle cycling. Consequently, the hair follicle cycle was disrupted and the hair was lost completely due to the loss of the Hr gene function in cetaceans. This suggests that cetaceans have evolved an effective and complex mechanism for hair loss.
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Affiliation(s)
- Zhuo Chen
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
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Kolokolchikova EG, Zhirkova EA, Golovatenko-abramov PK, Platonov ES, Smirnov SV, Botcharova VS. Morphofunctional Evaluation of the Effect of Transplantation of Allogeneic Fibroblasts on Healing of Burn Wounds in Albino Outbred Mice and Mutant Hr hr /Hr hr Mice. Bull Exp Biol Med 2012; 152:535-42. [DOI: 10.1007/s10517-012-1570-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Lee D, Kim SH, Chun JS, Joo MH, Kim JY, Hwang SW, Kang HJ, Park SW, Sung HS. Detection of a novel missense mutations in atrichia with papular lesions. Ann Dermatol 2011; 23:132-7. [PMID: 21747609 PMCID: PMC3130853 DOI: 10.5021/ad.2011.23.2.132] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 10/03/2010] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND Atrichia with papular lesions (APL) is a rare inherited disease characterized by early onset of total hair loss, followed by papular lesions over the extensor areas of the body. Recently, mutations in the human hairless (HR) gene have been implicated in its pathogenesis. The identification of mutations in the HR gene is important for differentiating between APL and alopecia universalis (AU). OBJECTIVE We compared the HR genes of patients with presumed AU who showed minimal or no response to treatment with the HR genes of healthy controls. METHODS The subjects were 11 patients with presumed AU who had not responded to treatments. Fifty healthy people were included as controls for molecular analysis. To screen for mutations, polymerase chain reaction was performed. RESULTS DNA analysis identified a novel heterozygous G-to-A transition at nucleotide position 191 in exon 5. The mutation was not found in the controls, other AU patients, or any unaffected family members except for the patients' mother and maternal grandfather, who were heterozygous HR gene carriers. CONCLUSION Our study identifies a novel missense mutation in exon 5 of the HR gene in a Korean APL patient previously diagnosed as AU.
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Affiliation(s)
- Deborah Lee
- Department of Dermatology, Busan Paik Hospital, College of Medicine, Inje University, Busan, Korea
| | - Sang-Hyun Kim
- Department of Dermatology, Busan Paik Hospital, College of Medicine, Inje University, Busan, Korea
| | - Ji-Sung Chun
- Department of Dermatology, Busan Paik Hospital, College of Medicine, Inje University, Busan, Korea
| | - Myeong-Hoon Joo
- Graduate School of Molecular & Biomedical Technology, Inje University, Gimhae, Korea
| | - Ji-Yeon Kim
- College of General Education, Inje University, Gimhae, Korea
| | - Seon-Wook Hwang
- Department of Dermatology, Busan Paik Hospital, College of Medicine, Inje University, Busan, Korea
| | | | | | - Ho-Suk Sung
- Department of Dermatology, Busan Paik Hospital, College of Medicine, Inje University, Busan, Korea
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Kolokolchikova EG, Zhirkova EA, Golovatenko-Abramov PK, Platonov ES, Botcharova VS, Khvatov VB. Morphofunctional evaluation of the effect of collagen-1-based dressing on skin regeneration after burn trauma in mice of two genetic strains. Bull Exp Biol Med 2010; 149:154-60. [PMID: 21113480 DOI: 10.1007/s10517-010-0896-1] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Morphofunctional evaluation of the effect of biological dressing with collagen-1 on healing of 3A degree burn wound in outbred and mutant Hr(hr)/Hr(hr)(hairless) mice was carried out by the histological method and optic radioautography. A pronounced stimulatory effect of the dressing on skin regeneration in mice was demonstrated. According to radioautography data, early dressing of the burn wounds in Hr(hr)/Hr(hr)mice led to active proliferation of epithelial cells in dermal cyst and vascular endotheliocytes. The possible mechanisms of the stimulatory effect of collagen-based dressing on wound healing are discussed.
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Mosconi T, Gruber T. Immunohistochemical comparison of whisker pad cutaneous innervation in Swiss Webster and hairless mice. Somatosens Mot Res 2010; 27:149-73. [PMID: 20961209 DOI: 10.3109/08990220.2010.513597] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
To establish the mouse mutant, hairless (Hr), as a useful model for future analyses of target-ending interactions, we assessed the cutaneous innervation in the whisker pad after loss of primary hair targets. Postnatal (P) development of fur in Hr begins similarly to that of "normal" Swiss Webster (SW) mice. Around P10, hairs are shed and the follicles rendered permanently incompetent. Hair loss progresses rostrocaudally until the entire skin is denuded. Substantial alterations in the distribution and density of sensory and autonomic endings in the mystacial pad vibrissal and intervibrissal fur innervation were discovered. Pilo-neural complexes innervating fur hairs were dismantled in Hr. Epidermal innervation in SW was rich; only a few endings expressed growth-associated protein-43 kdal (GAP), suggesting limited changes in axonal elongation. Innervation in Hr formed a dense layer passing upward through the thickened epidermis, with substantial increases among all types of endings. Vibrissal follicle-sinus complexes were also hyperinnervated. Endings in Hr vibrissae and fur were strongly GAP-positive, suggesting reorganization of innervation. Dermal and vascular autonomic innervation in both strains co-localized tyrosine hydroxylase and neuropeptide Y, but only in Hr did neuropeptide Y co-localize calcitonin gene-related peptide (CGRP) and express GAP immunolabeling. Stereological quantitation of trigeminal ganglia revealed no differences in neuron number between Hr and SW, although there were small increases in cell volume in Hr trigeminal ganglion cells. These results suggested that a form of collateral sprouting was active in Hr mystacial pads, not in response to local injury, but as a result of loss of primary target tissues.
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Affiliation(s)
- Tony Mosconi
- Department of Physical Therapy Education, Western University of Health Sciences, Pomona, CA 91766, USA.
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15
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Gueirard P, Tavares J, Thiberge S, Bernex F, Ishino T, Milon G, Franke-Fayard B, Janse CJ, Ménard R, Amino R. Development of the malaria parasite in the skin of the mammalian host. Proc Natl Acad Sci U S A 2010; 107:18640-5. [PMID: 20921402 DOI: 10.1073/pnas.1009346107] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The first step of Plasmodium development in vertebrates is the transformation of the sporozoite, the parasite stage injected by the mosquito in the skin, into merozoites, the stage that invades erythrocytes and initiates the disease. The current view is that, in mammals, this stage conversion occurs only inside hepatocytes. Here, we document the transformation of sporozoites of rodent-infecting Plasmodium into merozoites in the skin of mice. After mosquito bite, ∼50% of the parasites remain in the skin, and at 24 h ∼10% are developing in the epidermis and the dermis, as well as in the immunoprivileged hair follicles where they can survive for weeks. The parasite developmental pathway in skin cells, although frequently abortive, leads to the generation of merozoites that are infective to erythrocytes and are released via merosomes, as typically observed in the liver. Therefore, during malaria in rodents, the skin is not just the route to the liver but is also the final destination for many inoculated parasites, where they can differentiate into merozoites and possibly persist.
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Golovatenko-Abramov PK, Zhirkova EA, Kolokolchikova EG, Bocharova VS, Platonov ES. Dermal cysts participate in reparative regeneration of epidermis in Hr hr /Hr hr mice. Russ J Dev Biol 2010. [DOI: 10.1134/s1062360410040041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
Hair is a primary characteristic of mammals, and exerts a wide range of functions including thermoregulation, physical protection, sensory activity, and social interactions. The hair shaft consists of terminally differentiated keratinocytes that are produced by the hair follicle. Hair follicle development takes place during fetal skin development and relies on tightly regulated ectodermal-mesodermal interactions. After birth, mature and actively growing hair follicles eventually become anchored in the subcutis, and periodically regenerate by spontaneously undergoing repetitive cycles of growth (anagen), apoptosis-driven regression (catagen), and relative quiescence (telogen). Our molecular understanding of hair follicle biology relies heavily on mouse mutants with abnormalities in hair structure, growth, and/or pigmentation. These mice have allowed novel insights into important general molecular and cellular processes beyond skin and hair biology, ranging from organ induction, morphogenesis and regeneration, to pigment and stem cell biology, cell proliferation, migration and apoptosis. In this review, we present basic concepts of hair follicle biology and summarize important recent advances in the field.
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Affiliation(s)
- Marlon R Schneider
- Institute of Molecular Animal Breeding and Biotechnology, Gene Center, LMU Munich, Munich, Germany.
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18
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Higgins CA, Westgate GE, Jahoda CA. From telogen to exogen: mechanisms underlying formation and subsequent loss of the hair club fiber. J Invest Dermatol 2009; 129:2100-8. [PMID: 19340011 DOI: 10.1038/jid.2009.66] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The hair follicle has the unique capacity to undergo periods of growth, regression, and rest before regenerating itself to restart the cycle. This dynamic cycling capacity enables mammals to change their coats, and for hair length to be controlled on different body sites. More recently, the process of club fiber shedding has been described as a distinct cycle phase known as exogen, and proposed to be an active phase of the hair cycle. This review focuses on the importance of the shedding phase of the hair cycle and, in the context of current literature, analyzes the processes of club fiber formation, retention, and release, which may influence progression through exogen, particularly in relation to human hair.
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Benavides F, Oberyszyn TM, VanBuskirk AM, Reeve VE, Kusewitt DF. The hairless mouse in skin research. J Dermatol Sci 2008; 53:10-8. [PMID: 18938063 DOI: 10.1016/j.jdermsci.2008.08.012] [Citation(s) in RCA: 184] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 07/21/2008] [Accepted: 08/19/2008] [Indexed: 01/07/2023]
Abstract
The hairless (Hr) gene encodes a transcriptional co-repressor highly expressed in the mammalian skin. In the mouse, several null and hypomorphic Hr alleles have been identified resulting in hairlessness in homozygous animals, characterized by alopecia developing after a single cycle of relatively normal hair growth. Mutations in the human ortholog have also been associated with congenital alopecia. Although a variety of hairless strains have been developed, outbred SKH1 mice are the most widely used in dermatologic research. These unpigmented and immunocompetent mice allow for ready manipulation of the skin, application of topical agents, and exposure to UVR, as well as easy visualization of the cutaneous response. Wound healing, acute photobiologic responses, and skin carcinogenesis have been extensively studied in SKH1 mice and are well characterized. In addition, tumors induced in these mice resemble, both at the morphologic and molecular levels, UVR-induced skin malignancies in man. Two limitations of the SKH1 mouse in dermatologic research are the relatively uncharacterized genetic background and its outbred status, which precludes inter-individual transplantation studies.
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Affiliation(s)
- Fernando Benavides
- Department of Carcinogenesis, Science Park Research Division, University of Texas, MD Anderson Cancer Center, Smithville, TX 78957, USA
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Gu LH, Coulombe PA. Hedgehog signaling, keratin 6 induction, and sebaceous gland morphogenesis: implications for pachyonychia congenita and related conditions. Am J Pathol 2008; 173:752-61. [PMID: 18688029 DOI: 10.2353/ajpath.2008.071089] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Keratins 6a and b (K6a, K6b) belong to a subset of keratin genes with constitutive expression in epithelial appendages, and inducible expression in additional epithelia, when subjected to environmental challenges or disease. Mutations in K6a or K6b cause a broad spectrum of epithelial lesions that differentially affect nail, hair, and glands in humans. Some lesions reflect a loss of the structural support function shared by K6, other keratins, and intermediate filament proteins. The formation of sebaceous gland-derived epithelial cysts does not fit this paradigm, raising the question of the unique functions of different K6 isoforms in this setting. Here, we exploit a mouse model of constitutively expressed Gli2, a Hedgehog (Hh) signal effector, to show that K6a expression correlates with duct fate in sebaceous glands (SGs). Whether in the setting of Gli2 transgenic mice skin, which develops a prominent SG duct and additional pairs of highly branched SGs, or in wild-type mouse skin, K6a expression consistently coincides with Hh signaling in ductal tissue. Gli2 expression modestly transactivates a K6a promoter-driven reporter in heterologous systems. Our findings thus identify K6 as a marker of duct fate in SGs, partly in response to Hh signaling, with implications for the pathological expansion of SGs that arises in the context of certain keratin-based diseases and related disorders.
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Affiliation(s)
- Li-Hong Gu
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 21205, USA
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Pálmer HG, Martinez D, Carmeliet G, Watt FM. The vitamin D receptor is required for mouse hair cycle progression but not for maintenance of the epidermal stem cell compartment. J Invest Dermatol 2008; 128:2113-7. [PMID: 18337835 DOI: 10.1038/jid.2008.43] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Brancaz-Bouvier MV, Folco EJG, Salameire D, Romero Y, Iratni R, Nonchev S. The "bald Mill Hill" mutation in the mouse is associated with an abnormal, mislocalized HR bmh protein. J Invest Dermatol 2007; 128:311-21. [PMID: 17657241 DOI: 10.1038/sj.jid.5700998] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have previously identified a mutation in the mouse hairless locus-hairless rhino bald Mill Hill (Hr(rhbmh)). The genetic alteration in these mice consists in a large 296 bp deletion at the 3' part of the hairless gene (ID:MGI:3039558; J:89321). Here, we show that this deletion removes the stop codon and creates a new reading frame at the C terminus of the hairless protein, generating a larger mutant protein harboring an additional sequence of 117 amino acids. The mutant hairless gene mRNA is expressed during the embryonic and post-natal development of the hair follicle. The mutant protein is identified in bmh mouse skin at different stages of development by a specific antibody. We demonstrate that the HR bmh protein is able to interact with the vitamin D receptor (VDR), but is not able to repress VDR-mediated transactivation. Immunofluorescence analysis reveals that HR bmh protein displays an abnormal cellular localization in transfected cell lines, as well as in the epidermis and hair follicle of bmh mutant mice. We discuss the relevance of the hairless protein mis localization in cell signalling pathways and with respect to the specific skin phenotype of mouse hairless mutants.
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Liu Y, Das S, Olszewski RE, Carpenter DA, Culiat CT, Sundberg JP, Soteropoulos P, Liu X, Doktycz MJ, Michaud EJ, Voy BH. The Near-Naked Hairless (Hr) Mutation Disrupts Hair Formation but Is Not Due to a Mutation in the Hairless Coding Region. J Invest Dermatol 2007; 127:1605-14. [PMID: 17330134 DOI: 10.1038/sj.jid.5700755] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Near-naked hairless (Hr(N)) is a semi-dominant, spontaneous mutation that was suggested by allelism testing to be allelic with mouse Hairless (Hr). Hr(N) mice differ from other Hr mutants in that hair loss appears as the postnatal coat begins to emerge, rather than as an inability to regrow hair after the first catagen and that the mutation displays semi-dominant inheritance. We sequenced the Hr cDNA in Hr(N)/Hr(N) mice and characterized the pathological and molecular phenotypes to identify the basis for hair loss in this model. Hr(N)/Hr(N) mice exhibit dystrophic hairs that are unable to emerge consistently from the hair follicle, whereas Hr(N)/+ mice display a sparse coat of hair and a milder degree of follicular dystrophy than their homozygous littermates. DNA microarray analysis of cutaneous gene expression demonstrates that numerous genes are downregulated in Hr(N)/Hr(N) mice, primarily genes important for hair structure. By contrast, Hr expression is significantly increased. Sequencing the Hr-coding region, intron-exon boundaries, 5'- and 3'-untranslated region, and immediate upstream region did not reveal the underlying mutation. Therefore, Hr(N) does not appear to be an allele of Hr but may result from a mutation in a closely linked gene or from a regulatory mutation in Hr.
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Affiliation(s)
- Yutao Liu
- Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
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Lorenz K, Grashoff C, Torka R, Sakai T, Langbein L, Bloch W, Aumailley M, Fässler R. Integrin-linked kinase is required for epidermal and hair follicle morphogenesis. ACTA ACUST UNITED AC 2007; 177:501-13. [PMID: 17485490 PMCID: PMC2064816 DOI: 10.1083/jcb.200608125] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Integrin-linked kinase (ILK) links integrins to the actin cytoskeleton and is believed to phosphorylate several target proteins. We report that a keratinocyte-restricted deletion of the ILK gene leads to epidermal defects and hair loss. ILK-deficient epidermal keratinocytes exhibited a pronounced integrin-mediated adhesion defect leading to epidermal detachment and blister formation, disruption of the epidermal–dermal basement membrane, and the translocation of proliferating, integrin-expressing keratinocytes to suprabasal epidermal cell layers. The mutant hair follicles were capable of producing hair shaft and inner root sheath cells and contained stem cells and generated proliferating progenitor cells, which were impaired in their downward migration and hence accumulated in the outer root sheath and failed to replenish the hair matrix. In vitro studies with primary ILK-deficient keratinocytes attributed the migration defect to a reduced migration velocity and an impaired stabilization of the leading-edge lamellipodia, which compromised directional and persistent migration. We conclude that ILK plays important roles for epidermis and hair follicle morphogenesis by modulating integrin-mediated adhesion, actin reorganization, and plasma membrane dynamics in keratinocytes.
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Affiliation(s)
- Katrin Lorenz
- Department of Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, Germany
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Runkel F, Klaften M, Koch K, Böhnert V, Büssow H, Fuchs H, Franz T, Hrabé de Angelis M. Morphologic and molecular characterization of two novel Krt71 (Krt2-6g) mutations: Krt71rco12 and Krt71rco13. Mamm Genome 2006; 17:1172-82. [PMID: 17143583 DOI: 10.1007/s00335-006-0084-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2006] [Accepted: 08/30/2006] [Indexed: 12/17/2022]
Abstract
We have analyzed two novel mouse mutant strains, Rco12 and Rco13, displaying a wavy pelage and curly vibrissae that have been identified in an ENU screen for dominant mutations affecting the pelage. The mutations were mapped to mouse Chromosome 15 and identified as missense point mutations in the first exon of the Krt71 (formerly called Krt2-6g) gene causing alterations of amino acid residue 143 from alanine to glycine (Rco12) and residue 146 from isoleucine to phenylalanine. The morphologic analyses demonstrated that both mutations cause identical phenotypes leading to the formation of filamentous aggregates in Henle's and Huxley's layers of the inner root sheath (IRS) of the hair follicle that leads to the bending of the hair shaft. Both novel mutations are located in the immediate vicinity of previously identified mutations in murine Krt71 that cause similar phenotypes and alter the helix initiation motif of the keratin. The characterization of these mutants demonstrates the importance of this Krt71 domain for the formation of linear IRS intermediate filaments.
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Affiliation(s)
- Fabian Runkel
- Anatomisches Institut, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 10, D-53115 Bonn, Germany
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Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is among the most toxic pollutants known to date that serves as a prototype for a group of halogenated hydrocarbon compounds characterized by extraordinary environmental persistence and unique ability to concentrate in animal and human tissues. TCDD can elicit a complex array of pleiotropic adverse effects in humans, although chloracne, a specific type of acne-like skin disease, is the only consistent manifestation of dioxin intoxication, thus representing a 'hallmark' of TCDD exposure. Chloracne is considered to be one of the most specific and sensitive biomarkers of TCDD intoxication that allows clinical and epidemiological evaluation of exposure level at threshold doses. The specific cellular and molecular mechanisms involved in pathogenesis of chloracne are still unknown. In this review, we summarize the available clinical data on chloracne and recent progress in understanding the role of the dioxin-dependent pathway in the control of gene transcription and discuss molecular and cellular events potentially involved in chloracne pathogenesis. We propose that the dioxin-induced activation of skin stem cells and a shift in differentiation commitment of their progeny may represent a major mechanism of chloracne development.
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Abstract
BACKGROUND Congenital atrichia with papular lesions is a rare, recessively inherited condition of total alopecia, characterized clinically by complete and irreversible hair loss, which begins shortly after birth with the development of the papular lesions of keratin-filled cysts over an extensive area of the body. Mutations in the human hairless (HR) gene have been implicated in the pathogenesis of this disorder. OBJECTIVE To search for a mutation in human HR in a family with congenital atrichia. METHODS Linkage analysis was carried out using genotyping markers closely linked to congenital atrichia locus on chromosome 8p12. Subsequently, human HR was sequenced to identify a disease-causing mutation. RESULTS A novel 11 bp insertion mutation, G202 (InsCTTCCCCCAGG), in exon 2 of the hairless gene was identified in a Pakistani consanguineous family affected by congenital atrichia. The insertion results in the expansion of 11 bp tandem repeat, which introduces a translational frameshift leading to downstream premature termination codon. CONCLUSIONS This mutation is the first insertion mutation identified in the coding sequence of human HR. This extends our knowledge of mutations in HR that define the pathogenic basis of this disease.
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Affiliation(s)
- A Wali
- Department of Biological Sciences, Quaid-I-Azam University, Islamabad, Pakistan
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Beaudoin GMJ, Sisk JM, Coulombe PA, Thompson CC. Hairless triggers reactivation of hair growth by promoting Wnt signaling. Proc Natl Acad Sci U S A 2005; 102:14653-8. [PMID: 16195376 PMCID: PMC1253615 DOI: 10.1073/pnas.0507609102] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mammalian hair cycle involves periodic regeneration of a tiny organ, the hair follicle, through a stem-cell-mediated process. The Hairless (Hr) gene encodes a nuclear receptor corepressor (HR) that is essential for hair follicle regeneration, but its role in this process is unknown. Here, we demonstrate that transgenic expression of HR in progenitor keratinocytes rescues follicle regeneration in Hr(-/-) mice. We show that expression of Wise, a modulator of Wnt signaling, is repressed by HR in these cells, coincident with the timing of follicle regeneration. This work links HR and Wnt function, providing a model in which HR regulates the precise timing of Wnt signaling required for hair follicle regeneration.
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Affiliation(s)
- Gerard M J Beaudoin
- Kennedy Krieger Research Institute and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Abstract
Hair follicle cycling is a highly regulated and dynamic cellular process consisting of phases of growth, regression, and quiescence. The hairless (hr) gene encodes a nuclear factor that is highly expressed in the skin, where it appears to be an essential regulator during the regression in the catagen hair follicle. In hairless mice, as well as humans with congenital atrichia, the absence of hr protein initiates a premature and abnormal catagen due to defects in the signaling required for hair follicle remodeling. Here, we report that hr protein is a nuclear protein that is tightly associated with the nuclear matrix scaffold. Using a series of deletion constructs of the mouse hr gene, we monitored the sub-cellular localization of the recombinant protein by in situ immunolocalization and biochemical fractionation after nuclear matrix extraction of transiently transfected cells. We identified a novel nuclear matrix-targeting signal (NMTS) in the hr protein and mapped the domain to amino acid residues 111-186 of the mouse hr sequence. Furthermore, we provide evidence that this region not only mediates the interaction of hr with components of the nuclear architecture, but also specifies the sub-nuclear location of the hr protein to nuclear domains containing deacetylase activity. The N-terminal region directs hr to a speckled nuclear pattern that co-localizes with the histone deacetylase 3 (HDAC), but not with HDAC1 or HDAC7. Based on our findings, we propose that hr protein is part of a specific multi-protein repressor complex and that hr may be involved in chromatin remodeling.
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Affiliation(s)
- Karima Djabali
- Department of Dermatology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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Abstract
A novel autosomal recessive mutation arose spontaneously in a breeding colony of Chinese Kunming mice. The characteristics of these mutant mice include progressive irreversible hair loss soon after birth, rhinocerotic appearance, and shorter life span. Histological evaluation of skin revealed the homogeneous enlargement of utriculi, and the formation of several rows of large cysts. Sequencing the complete cDNA of the hairless gene identified two polymorphisms and a homozygous transition for a G-->A at nucleotide position 3110 (exon 12) leading to the substitution of tryptophan by a nonsense codon, designated W911X. This allele was named rhinocerotic and short-lived, with the symbol hr(rhsl). Addition of hairless gene mutation into the expanding hairless mutation database allows further development of genotype/phenotype correlations towards understanding inherited atrichia.
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Affiliation(s)
- Jin-Tao Zhang
- College of Life Sciences, Zhejiang University, and the State Conservation Center for Gene Resources of Endangered Wildlife, Zhejiang, China
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31
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Abstract
In mammals, hair follicles produce hairs that fulfill a number of functions including thermoregulation, collecting sensory information, protection against environmental trauma, social communication, and mimicry. Hair follicles develop as a result of epithelial-mesenchymal interactions between epidermal keratinocytes committed to hair-specific differentiation and cluster of dermal fibroblasts that form follicular papilla. During postnatal life, hair follicles show patterns of cyclic activity with periods of active growth and hair production (anagen), apoptosis-driven involution (catagen), and relative resting (telogen). During last decade, substantial progress has been achieved in delineating molecular mechanisms that control hair follicle development and cyclic activity. In this review, we summarize the data demonstrating that regulation of hair follicle development in the embryo and control of hair follicle growth during postnatal life are highly conserved and both require involvement of similar molecular mechanisms. Since many of the molecules that control hair follicle development and cycling are also involved in regulating morphogenesis and postnatal biology of other ectodermal derivatives, such as teeth, feathers, and mammary glands, basic principles and molecular mechanisms that govern hair follicle development and growth may also be applicable for other developmental systems.
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Nakamura Y, Fukami K, Yu H, Takenaka K, Kataoka Y, Shirakata Y, Nishikawa SI, Hashimoto K, Yoshida N, Takenawa T. Phospholipase Cdelta1 is required for skin stem cell lineage commitment. EMBO J 2003; 22:2981-91. [PMID: 12805213 PMCID: PMC162154 DOI: 10.1093/emboj/cdg302] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Phosphoinositide-specific phospholipase C (PLC) is a key enzyme in phosphoinositide turnover and is involved in a variety of physiological functions. Here we report that PLCdelta(1)-deficient mice undergo progressive hair loss in the first postnatal hair cycle. Epidermal hyperplasia was observed, and many hairs in the skin of PLCdelta(1)-deficient mice failed to penetrate the epidermis and became zigzagged owing to occlusion of the hair canal. Two major downstream signals of PLC, calcium elevation and protein kinase C activation, were impaired in the keratinocytes and skin of PLCdelta(1)-deficient mice. In addition, many cysts that had remarkable similarities to interfollicular epidermis, as well as hyperplasia of sebaceous glands, were observed. Furthermore, PLCdelta(1)-deficient mice developed spontaneous skin tumors that had characteristics of both interfollicular epidermis and sebaceous glands. From these results, we conclude that PLCdelta(1) is required for skin stem cell lineage commitment.
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Affiliation(s)
- Yoshikazu Nakamura
- Department of Biochemistry, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
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Abstract
Epithelial-mesenchymal interactions play pivotal roles in the morphogenesis of many organs and various types of appendages. During hair follicle development, extensive interactions between two embryologically different hair follicle compartments (epidermal keratinocytes and dermal papilla fibroblasts) lead to the formation of the hair shaft-producing mini-organ that shows cyclic activity during postnatal life with periods of active growth, involution and resting. During the hair cycle, the epithelium and the mesenchyme are regulated by a distinct set of molecular signals that are unique for every distinct phase of the hair cycle. In telogen hair follicles, epithelial-mesenchymal interactions are characterized by a predominance of inhibitory signals that retain the hair follicle in a quiescent state. During anagen, a large variety of growth stimulatory pathways are activated in the epithelium and in the mesenchyme, the coordination of which are essential for proper hair fiber formation. During catagen, the termination of anagen-specific signaling interactions between the epithelium and the mesenchyme leads to apoptosis in the hair follicle epithelium, while activation of selected signaling pathways promotes the transition of the dermal papilla into a quiescent state. The signaling exchange between the follicular epithelium and the mesenchyme is modulated by proteoglycans, such as versican, which may significantly enhance or reduce the biological activities of secreted growth stimulators. However, additional research will be required to bridge the gap between our current understanding of mechanisms underlying epithelial-mesenchymal interactions in hair follicles and the potential clinical application of growth modulators involved in those interactions. Further progress in this area of research will hopefully lead to the development of new drugs for the treatment of hair growth disorders.
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Abstract
Notch signaling is involved in the cell fate determination of various cell lineages. Notch interaction with its ligand induces the cleavage of its intracellular domain (IC), and the Notch IC translocates to the nucleus and binds to RBP-J to transactivate transcription of target genes. All four Notches in mammals bind to RBP-J to exert their transactivation activities. Notch is expressed in developing or differentiating epidermis and hairs, inhibits the terminal differentiation of the epidermis, and regulates hair differentiation. The common stem cells that reside in the upper portion of hair follicles (the bulge) contribute to epidermal and hair cell formation. However, it is unknown what determines whether hair follicular stem cells will become hairs or epidermis. Here we report that conditionally disrupting the mouse RBP-J gene in a mosaic pattern to avoid embryonic lethality of RBP-J-deficiency caused hair loss, epidermal hyperkeratinization, and epidermal cyst formation. Cyst formation is probably due to a combination of the aberrant fate determination of RBP-J-deficient stem cells to epidermal progenitors and their accelerated differentiation into epidermis. These results suggest that Notch/RBP-J signaling regulates the cell fate determination of hair follicular stem cells at the bulge region.
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Affiliation(s)
- Norio Yamamoto
- Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
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35
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Abstract
The outer surface of the hand, limb and body is covered by the epidermis, which is elaborated into a number of specialized appendages, evolved not only to protect and reinforce the skin but also for social signalling. The most prominent of these appendages is the hair follicle. Hair follicles are remarkable because of their prolific growth characteristics and their complexity of differentiation. After initial embryonic morphogenesis, the hair follicle undergoes repeated cycles of regression and regeneration throughout the lifetime of the organism. Studies of mouse mutants with hair loss phenotypes have suggested that the mechanisms controlling the hair cycle probably involve many of the major signalling molecules used elsewhere in development, although the complete pathway of hair follicle growth control is not yet understood. Mouse studies have also led to the discovery of genes underlying several human disorders. Future studies of mouse hair-loss mutants are likely to benefit the understanding of human hair loss as well as increasing our knowledge of mechanisms controlling morphogenesis and tumorigenesis.
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Affiliation(s)
- Rebecca M Porter
- Cancer Research UK Cell Structure Research Group, School of Life Sciences, MSI/WTB Complex, University of Dundee, Dundee DD1 5EH, UK.
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Zlotogorski A, Martinez-Mir A, Green J, Lamdagger H, Panteleyevdagger AA, Sinclair R, Christiano AM. Evidence for pseudodominant inheritance of atrichia with papular lesions. J Invest Dermatol 2002; 118:881-6. [PMID: 11982769 DOI: 10.1046/j.1523-1747.2002.01740.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Atrichia with papular lesions is a rare form of total alopecia, in which mutations in the hairless gene have been shown to underlie the phenotype. In the literature to date, atrichia with papular lesions has generally been reported to be inherited in an autosomal recessive manner. A few rare cases exist, however, in which parent-to-child transmission of atrichia with papular lesions has been documented. In this study, further investigations were carried out into the molecular basis of atrichia with papular lesions in a family with mother-to-son transmission by searching for mutations in the human hairless gene. Specific ally, we wanted to determine whether this case truly represented an example of dominantly inherited atrichia with papular lesions, or whether another mode of inheritance might be responsible for the disorder in this kindred. Pseudodominant inheritance, for example, occurs when an individual with a known recessive disorder has a clinically unaffected partner, but then unexpectedly gives birth to children who are affected with the same recessive disorder as the affected parent, and can easily be distinguished from classical dominant inheritance with molecular diagnosis and haplotype analysis. In the family reported here, we have determined that both the mother and son are, in fact, homozygous for a novel mutation in the hairless gene, R33X. We provide the first evidence for pseudodominant inheritance in atrichia with papular lesions, and at the same time extend our knowledge of pathogenetic mutations in the human hairless gene. Importantly, this information allows revisions in genetic counseling for risk of transmission for individuals in the family, previously impossible in the absence of knowing the genetic basis of atrichia with papular lesions in this unusual kindred.
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Affiliation(s)
- Abraham Zlotogorski
- Department of Dermatology, Hadassah University Medical Center, Jerusalem, Israel
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37
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Abstract
Congenital atrichia with papular lesions is a rare, autosomal recessive form of total alopecia and mutations in the hairless (hr) gene have been implicated in this disorder. Published estimates of the prevalence of this disorder remain surprisingly low considering pathogenetic mutations in hr have been found in distinct populations around the world. Therefore, it is likely that congenital atrichia with papular lesions is more common than previously thought and is often mistaken for the putative autoimmune form of alopecia universalis. To clarify this discrepancy, we propose criteria for the clinical diagnosis of congenital atrichia with papular lesions. Among these is the novel report of the consistent observation of hypopigmented whitish streaks on the scalp surface of affected individuals. Additionally, we report the identification of a novel missense mutation in hr from a family of Arab Palestinian origin that exhibits the pathognomonic features of atrichia with papular lesions. Collectively, we anticipate that an increased recognition of this disorder will result in more accurate diagnosis and the sparing of unnecessarily treatment to patients.
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38
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Abstract
The epidermis is populated by stem cells that produce daughters that differentiate to form the interfollicular epidermis, hair follicles and sebaceous glands. Diffusible factors, cell-cell contact and extracellular matrix proteins are all important components of the microenvironment of individual stem cells and profoundly affect the differentiation pathways selected by their progeny. Here, we summarize what is known about stem-cell populations and lineage relationships within the epidermis. We also present evidence that postnatal epidermis can be reprogrammed, altering the number and location of cells that differentiate along specific epidermal lineages.
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Affiliation(s)
- Catherin Niemann
- Keratinocyte Laboratory, Cancer Research UK, 44 Lincoln's Inn Fields, WC2A 3PX., London, UK
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39
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Abstract
Numerous transgenic, targeted mutagenesis (so-called knockouts), conditional (so-called "gene switch") and spontaneous mutant mice develop abnormal hair phenotypes. The number of mice that exhibit such abnormalities is increasing exponentially as genetic engineering methods become routine. Since defined abnormalities in hair follicle morphogenesis, cycling and/or structure in such mutant mice provide important clues to the as yet poorly understood functional roles of many gene products, it is useful to summarize and classify these mutant mice according to their hair phenotype. This review provides a corresponding, annotated table of mutant mice with hair abnormalities, classifying the latter into 6 categories, 1) abnormally low number of hair follicles, 2) disorders of hair morphogenesis, 3) of hair follicle cycling, 4) of hair follicle structure 5) of sebaceous gland structure, and 6) hair growth disorders as a consequence of immunological abnormalities. This annotated table should serve as a useful source of reference for anyone who is interested in the molecular controls of hair growth, for investigators who are looking for mouse models to explore or compare the functional activities of their gene of interest, and for comparing the hair phenotype of newly generated mouse mutants with existing ones.
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Affiliation(s)
- M Nakamura
- Department of Dermatology, University Hospital Eppendorf, University of Hamburg, Martinistrasse 52, D-20246, Hamburg, Germany
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40
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Abstract
Congenital atrichia with papular lesions is a rare, autosomal recessive form of total alopecia and mutations in the hairless (hir) gene have been implicated in this disorder. Published estimates of the prevalence of this disorder remain surprisingly low considering pathogenetic mutations in hir have been found in distinct ethnicities around the world. Therefore, it is likely that congenital atrichia with papular lesions is far more common than previously thought and is often mistaken for its phenocopy, the putative autoimmune form of alopecia universalis. To clarify this discrepancy, we propose criteria for the clinical diagnosis of congenital atrichia with papular lesions. Among these is the novel report of the consistent observation of hypopigmented whitish streaks on the scalp surface of affected individuals. Additionally, we report the identification of a novel missense mutation in hir from a family of Arab Palestinian origin that exhibits the pathognomonic features of atrichia with papular lesions. Collectively, we anticipate that an increased recognition of this disorder will result in more accurate diagnosis and the sparing of unnecessarily treatment to patients.
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Affiliation(s)
- A Zlotogorski
- Department of Dermatology, Hadassah Medical Center, Jerusalem, Israel
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Chidgey M, Brakebusch C, Gustafsson E, Cruchley A, Hail C, Kirk S, Merritt A, North A, Tselepis C, Hewitt J, Byrne C, Fassler R, Garrod D. Mice lacking desmocollin 1 show epidermal fragility accompanied by barrier defects and abnormal differentiation. J Cell Biol 2001; 155:821-32. [PMID: 11714727 PMCID: PMC2150874 DOI: 10.1083/jcb.200105009] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2001] [Revised: 08/22/2001] [Accepted: 10/15/2001] [Indexed: 11/22/2022] Open
Abstract
The desmosomal cadherin desmocollin (Dsc)1 is expressed in upper epidermis where strong adhesion is required. To investigate its role in vivo, we have genetically engineered mice with a targeted disruption in the Dsc1 gene. Soon after birth, null mice exhibit flaky skin and a striking punctate epidermal barrier defect. The epidermis is fragile, and acantholysis in the granular layer generates localized lesions, compromising skin barrier function. Neutrophils accumulate in the lesions and further degrade the tissue, causing sloughing (flaking) of lesional epidermis, but rapid wound healing prevents the formation of overt lesions. Null epidermis is hyperproliferative and overexpresses keratins 6 and 16, indicating abnormal differentiation. From 6 wk, null mice develop ulcerating lesions resembling chronic dermatitis. We speculate that ulceration occurs after acantholysis in the fragile epidermis because environmental insults are more stringent and wound healing is less rapid than in neonatal mice. This dermatitis is accompanied by localized hair loss associated with formation of utriculi and dermal cysts, denoting hair follicle degeneration. Possible resemblance of the lesions to human blistering diseases is discussed. These results show that Dsc1 is required for strong adhesion and barrier maintenance in epidermis and contributes to epidermal differentiation.
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Affiliation(s)
- M Chidgey
- School of Biological Sciences, University of Manchester, Manchester M13 9PT, UK
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42
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Abstract
The concept that stem cells are controlled by particular microenvironments known as 'niches' has been widely invoked. But niches have remained largely a theoretical construct because of the difficulty of identifying and manipulating individual stem cells and their surroundings. Technical advances now make it possible to characterize small zones that maintain and control stem cell activity in several organs, including gonads, skin and gut. These studies are beginning to unify our understanding of stem cell regulation at the cellular and molecular levels, and promise to advance efforts to use stem cells therapeutically.
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Affiliation(s)
- A Spradling
- HHMI/Department of Embryology, Carnegie Institution of Washington, Baltimore, Maryland 21210, USA
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43
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Hu Z, Gomes I, Horrigan SK, Kravarusic J, Mar B, Arbieva Z, Chyna B, Fulton N, Edassery S, Raza A, Westbrook CA. A novel nuclear protein, 5qNCA (LOC51780) is a candidate for the myeloid leukemia tumor suppressor gene on chromosome 5 band q31. Oncogene 2001; 20:6946-54. [PMID: 11687974 DOI: 10.1038/sj.onc.1204850] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2001] [Revised: 07/09/2001] [Accepted: 07/17/2001] [Indexed: 11/08/2022]
Abstract
Interstitial deletion or loss of chromosome 5, del(5q) or -5, is a frequent finding in myeloid leukemias and myelodysplasias, suggesting the presence of a tumor suppressor gene within the deleted region. In our search for this gene, we identified a candidate, 5qNCA (LOC51780), which lies within a consistently-deleted segment of 5q31. 5qNCA expresses a 7.2-kb transcript with a 5286-bp open reading frame which is present at high levels in heart, skeletal muscle, kidney, placenta, and liver as well as CD34+ cells and AML cell lines. 5qNCA encodes a 191-kD nuclear protein which contains a highly-conserved C-terminus containing a zinc finger with the unique spacing Cys-X2-Cys-X7-His-X2-Cys-X2-Cys-X4-Cys-X2-Cys and a jmjC domain, which is often found in proteins that regulate chromatin remodeling. Expression of 5qNCA in a del(5q) cell line results in suppression of clonogenic growth. Preliminary sequence results in AML and MDS samples and cell lines has revealed a possible mutation in the KG-1 cell line resulting in a THR to ALA substitution that has not been found in over 100 normal alleles to date. We propose 5qNCA is a good candidate for the del(5q) tumor suppressor gene based on its predicted function and growth suppressive activities, and suggest that further mutational and functional study of this interesting gene is warranted.
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MESH Headings
- Acute Disease
- Amino Acid Motifs
- Amino Acid Sequence
- Cell Division
- Chromosomes, Human, Pair 5
- Cloning, Molecular
- Genes, Tumor Suppressor
- Humans
- Jumonji Domain-Containing Histone Demethylases
- Leukemia, Myeloid/genetics
- Leukemia, Myeloid/metabolism
- Leukemia, Myeloid/pathology
- Molecular Sequence Data
- Mutation
- Myelodysplastic Syndromes/genetics
- Myelodysplastic Syndromes/metabolism
- Myelodysplastic Syndromes/pathology
- Nuclear Proteins/chemistry
- Nuclear Proteins/genetics
- Nuclear Proteins/physiology
- RNA, Neoplasm/biosynthesis
- Sequence Homology, Amino Acid
- Tissue Distribution
- Tumor Cells, Cultured
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Affiliation(s)
- Z Hu
- Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60607-7170, USA
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44
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Abstract
Recent genetic and molecular studies of hair follicle (HF) biology have provided substantial insight; however, the molecular data, including expression patterns, cannot be properly appreciated without an understanding of the basic cellular rearrangements and interactions that underpin HF cyclic transformations. We present a novel interpretation of the major cellular processes that take place during HF cycling – the hypothesis of hair follicle predetermination. This hypothesis is an extension of previous models of HF cellular kinetics but has two critical modifications: the dual origin of the cycling portion of the HF, and the timing of the recruitment of stem cells. A compilation of evidence suggests that the ascending portion of the HF (hair shaft and inner root sheath) arises not from bulge-located HF stem cells that contribute to the formation of only the outer root sheath (ORS), but instead from the germinative cells localized in the secondary hair germ. In middle anagen, upon completion of the downward growth of the HF, cells derived from the bulge region migrate downward along the ORS to reside at the periphery of the HF bulb as a distinct, inactive cell population that has specific patterns of gene expression - ‘the lateral disc’. These cells survive catagen-associated apoptosis and, under the direct influence of the follicular papilla (FP), transform into the hair germ and acquire the ability to respond to FP signaling and produce a new hair. Thus, we propose that the specific sensitivity of germ cells to FP signaling and their commitment to produce the ascending HF layers are predetermined by the previous hair cycle during the process of transformation of bulge-derived lateral disc cells into the secondary hair germ.
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Affiliation(s)
- A A Panteleyev
- Department of Dermatology, Columbia University, College of Physicians and Surgeons, 630 W. 168th Street, Vanderbilt Clinic VC-1526, New York, NY 10032, USA.
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45
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Miller J, Djabali K, Chen T, Liu Y, Ioffreda M, Lyle S, Christiano AM, Holick M, Cotsarelis G. Atrichia caused by mutations in the vitamin D receptor gene is a phenocopy of generalized atrichia caused by mutations in the hairless gene. J Invest Dermatol 2001; 117:612-7. [PMID: 11564167 DOI: 10.1046/j.0022-202x.2001.01438.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Generalized atrichia with papules is a rare disorder characterized by loss of hair shortly after birth and development of cutaneous cysts. Mutations in the hairless gene (HR) cause this phenotype in both mouse and human. Here we present a case of atrichia with papules in a patient with a normal HAIRLESS gene but with mutations in both alleles of the VITAMIN D RECEPTOR. The patient exhibited vitamin D resistant rickets, which was confirmed by an absent response of her fibroblasts to 1,25-dihydroxyvitamin D3 in vitro. Similar to individuals with HAIRLESS mutations, her skin showed an absence of normal hair follicles and the presence of follicular remnants and cysts. The cyst epithelium contained keratin-15- and keratin-17-positive cells suggesting derivation from the hair follicle bulge and the presence of epithelial stem cells. Although hair loss has been reported in association with hereditary vitamin D resistant rickets, we now characterize this alopecia as clinically and pathologically indistinguishable from generalized atrichia with papules, which was previously thought to be caused only by mutations in HAIRLESS. These findings suggest that VDR and HR, which are both zinc finger proteins, may be in the same genetic pathway that controls postnatal cycling of the hair follicle.
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Affiliation(s)
- J Miller
- Department of Dermatology, Hershey Medical Center, Hershey, Pennsylvania, USA
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San Jose I, García-Atares N, Pelaez B, Cabo R, Esteban I, Vega JA, Represa J. Reduction of glial fibrillary acidic protein-immunoreactive astrocytes in some brain areas of old hairless rhino-j mice (hr-rh-j). Neurosci Lett 2001; 309:81-4. [PMID: 11502350 DOI: 10.1016/s0304-3940(01)02041-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Mutations in the hairless (hr) gene of mice result in hair follicle and other epithelial defects. The hr gene is expressed at high levels in the brain where it probably participates in the survival and maintenance of some neuronal populations, but whether it also supports glial populations of the central nervous system has been not investigated. To clarify this, quantitative immunohistochemistry for astrocytes (glial fibrillary acidic protein (GFAP)) and microglial cells (CD11b macrophage antigen) was used in the brain of a mutant mouse strain, the hairless (hr-rh-j) type, which carries the homozygous hr gene rhino mutation. The glial cell density was assessed in the cerebral cortex, hippocampus, striatum, hypothalamus and cerebellum of young (3 months) and old (9 months) hr-rh-j mice. No significant differences were found between young wild-type and hr-rh-j mice. The density of GFAP immunoreactive astrocytes normally increased as a function of age, but in older hr-rh-j mice there was a severe reduction (P<0.01) in the striatum, hypothalamus, and hippocampus. Conversely, the microglial cells were insensible to aging or to hr-rh-j mutation. These results suggest that the hr gene is involved in the maintenance of the GFAP immunoreactive cells in some cerebral areas. Nevertheless, because these animals do not show any neurological signs, the functional significance of the present findings remains to be established.
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Affiliation(s)
- I San Jose
- Departamento de Anatomía Humana, Universidad de Valladolid, Valladolid, Spain
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47
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Müller-Röver S, Handjiski B, van der Veen C, Eichmüller S, Foitzik K, McKay IA, Stenn KS, Paus R. A comprehensive guide for the accurate classification of murine hair follicles in distinct hair cycle stages. J Invest Dermatol 2001; 117:3-15. [PMID: 11442744 DOI: 10.1046/j.0022-202x.2001.01377.x] [Citation(s) in RCA: 953] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Numerous strains of mice with defined mutations display pronounced abnormalities of hair follicle cycling, even in the absence of overt alterations of the skin and hair phenotype; however, in order to recognize even subtle, hair cycle-related abnormalities, it is critically important to be able to determine accurately and classify the major stages of the normal murine hair cycle. In this comprehensive guide, we present pragmatic basic and auxiliary criteria for recognizing key stages of hair follicle growth (anagen), regression (catagen) and quiescence (telogen) in C57BL/6NCrlBR mice, which are largely based on previous work from other authors. For each stage, a schematic drawing and representative micrographs are provided in order to illustrate these criteria. The basic criteria can be employed for all mouse strains and require only routine histochemical techniques. The auxiliary criteria depend on the immunohistochemical analysis of three markers (interleukin-1 receptor type I, transforming growth factor-beta receptor type II, and neural cell-adhesion molecule), which allow a refined analysis of anatomical hair follicle compartments during all hair cycle stages. In contrast to prior staging systems, we suggest dividing anagen III into three distinct substages, based on morphologic differences, onset and progression of melanogenesis, and the position of the dermal papilla in the subcutis. The computer-generated schematic representations of each stage are presented with the aim of standardizing reports on follicular gene and protein expression patterns. This guide should become a useful tool when screening new mouse mutants or mice treated with pharmaceuticals for discrete morphologic abnormalities of hair follicle cycling in a highly reproducible, easily applicable, and quantifiable manner.
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Affiliation(s)
- S Müller-Röver
- Department of Dermatology, University Hospital Eppendorf, University of Hamburg, Hamburg, Germany
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48
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Abstract
Atrichia with papular lesions is a rare inherited skin disorder characterized by congenital atrichia with numerous papules. We describe a 27-year-old woman with atrichia, who had numerous papules on her scalp, nape, and axillae. Histologically, many keratinous cysts were seen in the middermis of a skin specimen from the nape. Electron microscopy showed that the developing keratinocytes in the walls of some cysts were rich in glycogen granules and had epidermoid keratinization with formation of keratohyaline granules and that laminated bodies were formed before keratinization. Langerhans cells were often seen in the walls of the cysts. In addition, a broad glassy vitreous layer surrounded the cyst wall. From these findings, it was suggested that the cystic lesions might have originated from immature or incomplete hair follicles. In particular, the structure of the cyst wall corresponded well to infundibular and/or isthmal portions of the outer root sheath of the hair follicle.
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Affiliation(s)
- K Nomura
- Department of Dermatology, Aomori Prefectural Central Hospital, Higashi-Tsukurimichi 2-1-1, Aomori 030-0913, Japan.
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49
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Abstract
Nearly 50 years ago, Chase published a review of hair cycling in which he detailed hair growth in the mouse and integrated hair biology with the biology of his day. In this review we have used Chase as our model and tried to put the adult hair follicle growth cycle in perspective. We have tried to sketch the adult hair follicle cycle, as we know it today and what needs to be known. Above all, we hope that this work will serve as an introduction to basic biologists who are looking for a defined biological system that illustrates many of the challenges of modern biology: cell differentiation, epithelial-mesenchymal interactions, stem cell biology, pattern formation, apoptosis, cell and organ growth cycles, and pigmentation. The most important theme in studying the cycling hair follicle is that the follicle is a regenerating system. By traversing the phases of the cycle (growth, regression, resting, shedding, then growth again), the follicle demonstrates the unusual ability to completely regenerate itself. The basis for this regeneration rests in the unique follicular epithelial and mesenchymal components and their interactions. Recently, some of the molecular signals making up these interactions have been defined. They involve gene families also found in other regenerating systems such as fibroblast growth factor, transforming growth factor-beta, Wnt pathway, Sonic hedgehog, neurotrophins, and homeobox. For the immediate future, our challenge is to define the molecular basis for hair follicle growth control, to regenerate a mature hair follicle in vitro from defined populations, and to offer real solutions to our patients' problems.
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Affiliation(s)
- K S Stenn
- Beauty Genome Sciences Inc., Skillman, New Jersey, USA.
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50
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Abstract
The hair follicle is finally, after remaining a mystery for many years, beginning to yield some of its molecular secrets. The past decade has seen unprecedented and ever quickening advances in understanding the molecular genetics of the many single gene disorders, which have alopecia as a major feature. This article reviews recent novel clinical and experimental observations, which have shed new light on the basic molecular mechanisms underlying hair morphogenesis, differentiation, keratinization and cycling. We consider recent progress in understanding structural hair defects and complex traits and consider where future developments are likely to occur.
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Affiliation(s)
- A D Irvine
- Department of Dermatology, Great Ormond Street Hospital for Children, London, UK.
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