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Stadtmauer DJ, Wagner GP. The mammary hair of Monodelphis domestica and homology of the mammary pilosebacous unit. J Morphol 2024; 285:e21769. [PMID: 39188032 DOI: 10.1002/jmor.21769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2024] [Revised: 08/03/2024] [Accepted: 08/09/2024] [Indexed: 08/28/2024]
Abstract
The unitary mammary gland is a synapomorphy of therian mammals and is thought to have evolved from the pilosebaceous organ in the mammalian stem lineage from which the lactogenic patch of monotremes is also derived. One of the key lines of evidence for the homology of the nipple and the lactogenic patch is that marsupials have retained a transient hair associated with developing mammary glands. However, these structures have not been documented since the early 20th-century drawings of Ernst Bresslau. In this study, we examine the developing mammary organs of Monodelphis domestica and document the presence of mammary hairs in 12-week-old females, as well as their absence after 18 weeks of age. Histochemical staining for cystine confirms the structures as keratinized hairs. Milk ducts of both juvenile and adult nipples show a division between KRT18+ luminal epithelium and KRT14+ ACTA2+ myoepithelium. These patterns match those in eutherians and suggest a conserved ductal morphology and mechanism of milk expulsion. Finally, PTHLH, a peptide hormone which promotes homeotic transformation of hairy skin into hairless nipples in the mouse, was detected in the Monodelphis milk duct during the mammary hair stage, suggesting that the mutual exclusivity of "hairless nipple" and "hair" organ identity is derived in eutherian mammals. These results reveal shared characteristics of the M. domestica nipple with both the eutherian nipple and the pilosebaceous organ, consistent with the evolutionary derivation of the mammary gland from an ancestral hair organ via developmental individualization of pilosebaceous and mammary identities.
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Affiliation(s)
- Daniel J Stadtmauer
- Department of Ecology & Evolutionary Biology, Yale University, New Haven, Connecticut, USA
- Department of Evolutionary Biology, University of Vienna, Vienna, Austria
| | - Günter P Wagner
- Department of Ecology & Evolutionary Biology, Yale University, New Haven, Connecticut, USA
- Department of Evolutionary Biology, University of Vienna, Vienna, Austria
- Department of Animal Science, Texas A&M University, College Station, Texas, USA
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2
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Dingwall HL, Tomizawa RR, Aharoni A, Hu P, Qiu Q, Kokalari B, Martinez SM, Donahue JC, Aldea D, Mendoza M, Glass IA, Wu H, Kamberov YG. Sweat gland development requires an eccrine dermal niche and couples two epidermal programs. Dev Cell 2024; 59:20-32.e6. [PMID: 38096824 PMCID: PMC10872420 DOI: 10.1016/j.devcel.2023.11.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 10/02/2023] [Accepted: 11/14/2023] [Indexed: 12/22/2023]
Abstract
Eccrine sweat glands are indispensable for human thermoregulation and, similar to other mammalian skin appendages, form from multipotent epidermal progenitors. Limited understanding of how epidermal progenitors specialize to form these vital organs has precluded therapeutic efforts toward their regeneration. Herein, we applied single-nucleus transcriptomics to compare the expression content of wild-type, eccrine-forming mouse skin to that of mice harboring a skin-specific disruption of Engrailed 1 (En1), a transcription factor that promotes eccrine gland formation in humans and mice. We identify two concurrent but disproportionate epidermal transcriptomes in the early eccrine anlagen: one that is shared with hair follicles and one that is En1 dependent and eccrine specific. We demonstrate that eccrine development requires the induction of a dermal niche proximal to each developing gland in humans and mice. Our study defines the signatures of eccrine identity and uncovers the eccrine dermal niche, setting the stage for targeted regeneration and comprehensive skin repair.
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Affiliation(s)
- Heather L Dingwall
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Reiko R Tomizawa
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Adam Aharoni
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Peng Hu
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Qi Qiu
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Blerina Kokalari
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | | | - Joan C Donahue
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Daniel Aldea
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Meryl Mendoza
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Ian A Glass
- Department of Pediatrics, University of Washington, Seattle, WA, USA
| | - Hao Wu
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA
| | - Yana G Kamberov
- Department of Genetics, Perelman School of Medicine, Philadelphia, PA, USA.
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3
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Dhouailly D. Evo Devo of the Vertebrates Integument. J Dev Biol 2023; 11:25. [PMID: 37367479 DOI: 10.3390/jdb11020025] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/19/2023] [Accepted: 05/21/2023] [Indexed: 06/28/2023] Open
Abstract
All living jawed vertebrates possess teeth or did so ancestrally. Integumental surface also includes the cornea. Conversely, no other anatomical feature differentiates the clades so readily as skin appendages do, multicellular glands in amphibians, hair follicle/gland complexes in mammals, feathers in birds, and the different types of scales. Tooth-like scales are characteristic of chondrichthyans, while mineralized dermal scales are characteristic of bony fishes. Corneous epidermal scales might have appeared twice, in squamates, and on feet in avian lineages, but posteriorly to feathers. In contrast to the other skin appendages, the origin of multicellular glands of amphibians has never been addressed. In the seventies, pioneering dermal-epidermal recombination between chick, mouse and lizard embryos showed that: (1) the clade type of the appendage is determined by the epidermis; (2) their morphogenesis requires two groups of dermal messages, first for primordia formation, second for appendage final architecture; (3) the early messages were conserved during amniotes evolution. Molecular biology studies that have identified the involved pathways, extending those data to teeth and dermal scales, suggest that the different vertebrate skin appendages evolved in parallel from a shared placode/dermal cells unit, present in a common toothed ancestor, c.a. 420 mya.
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Affiliation(s)
- Danielle Dhouailly
- Department of Biology and Chemistry, Institute for Advanced Biosciences, University Grenoble-Alpes, 38700 La Tronche, France
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4
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Matouskova K, Szabo GK, Daum J, Fenton SE, Christiansen S, Soto AM, Kay JE, Cardona B, Vandenberg LN. Best practices to quantify the impact of reproductive toxicants on development, function, and diseases of the rodent mammary gland. Reprod Toxicol 2022; 112:51-67. [PMID: 35764275 PMCID: PMC9491517 DOI: 10.1016/j.reprotox.2022.06.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 06/13/2022] [Accepted: 06/23/2022] [Indexed: 11/30/2022]
Abstract
Work from numerous fields of study suggests that exposures to hormonally active chemicals during sensitive windows of development can alter mammary gland development, function, and disease risk. Stronger links between many environmental pollutants and disruptions to breast health continue to be documented in human populations, and there remain concerns that the methods utilized to identify, characterize, and prioritize these chemicals for risk assessment and risk management purposes are insufficient. There are also concerns that effects on the mammary gland have been largely ignored by regulatory agencies. Here, we provide technical guidance that is intended to enhance collection and evaluation of the mammary gland in mice and rats. We review several features of studies that should be controlled to properly evaluate the mammary gland, and then describe methods to appropriately collect the mammary gland from rodents. Furthermore, we discuss methods for preparing whole mounted mammary glands and numerous approaches that are available for the analysis of these samples. Finally, we conclude with several examples where analysis of the mammary gland revealed effects of environmental toxicants at low doses. Our work argues that the rodent mammary gland should be considered in chemical safety, hazard and risk assessments. It also suggests that improved measures of mammary gland outcomes, such as those we present in this review, should be included in the standardized methods evaluated by regulatory agencies such as the test guidelines used for identifying reproductive and developmental toxicants.
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Affiliation(s)
- Klara Matouskova
- Department of Environmental Health Sciences, School of Public Health & Health Sciences, University of Massachusetts Amherst, Amherst, MA, USA.
| | - Gillian K Szabo
- Department of Environmental Health Sciences, School of Public Health & Health Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Jessica Daum
- Department of Environmental Health Sciences, School of Public Health & Health Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Suzanne E Fenton
- Mechanistic Toxicology Branch, Division of the National Toxicology Program, National Institutes of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Sofie Christiansen
- National Food Institute, Technical University of Denmark, Kgs, Lyngby DK 2800, Denmark
| | - Ana M Soto
- Tufts University School of Medicine, Boston, MA, USA
| | | | | | - Laura N Vandenberg
- Department of Environmental Health Sciences, School of Public Health & Health Sciences, University of Massachusetts Amherst, Amherst, MA, USA.
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5
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Shi R, Li S, Liu P, Zhang S, Wu Z, Wu T, Gong S, Wan Y. Identification of key genes and signaling pathways related to Hetian sheep wool density by RNA-seq technology. PLoS One 2022; 17:e0265989. [PMID: 35613128 PMCID: PMC9132291 DOI: 10.1371/journal.pone.0265989] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 03/14/2022] [Indexed: 11/18/2022] Open
Abstract
Hetian sheep is a breed of sheep unique to the Hetian area of Xinjiang whose wool is used for producing blankets. Individual differences and hair follicle density are the key factors affecting wool production. Therefore, this study aimed to assess the Hetian sheep having different wool densities to statistically analyze the wool traits and hair follicle parameters. Furthermore, the transcriptome sequencing analysis was performed on the skins with different wool densities. The results showed that wool quantity and total hair follicle density of the high wool density sheep was significantly higher than low wool density sheep. The sheepskin with high wool density was found to grow more and finer wool than sheepskin with low wool density. A total of 1,452 differentially expressed genes were screened from the two sets of samples, including 754 upregulated and 698 downregulated genes. The differentially expressed genes were involved in the TGF-β/BMP and MAPK signaling pathways related to hair growth. Eleven differentially expressed genes belonging to the KAPs and KIFs might affect the fineness of the wool. The key genes, like the TNF, MAP2K2, INHBA, FST, PTPN11, MAP3K7, KIT, and BMPR1A, were found to probably affect the growth and density of the wool. The qPCR verified eight genes related to the MAPK pathway whose gene expression trends were consistent with the transcriptome sequencing results. This study furnishes valuable resources for enhancing the quality and production of wool in the Hetian sheep.
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Affiliation(s)
- Ruijun Shi
- Key Laboratory of Protection & Utilization of Biological Resources in Tarim Basin, College of Life Sciences, Tarim University, Alar, China
| | - Shuwei Li
- Key Laboratory of Protection & Utilization of Biological Resources in Tarim Basin, College of Life Sciences, Tarim University, Alar, China
- * E-mail:
| | - Penggang Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Shuhui Zhang
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Taian, China
| | - Zhenhui Wu
- Key Laboratory of Protection & Utilization of Biological Resources in Tarim Basin, College of Life Sciences, Tarim University, Alar, China
| | - Tinghui Wu
- Key Laboratory of Protection & Utilization of Biological Resources in Tarim Basin, College of Life Sciences, Tarim University, Alar, China
| | - Shujuan Gong
- Key Laboratory of Protection & Utilization of Biological Resources in Tarim Basin, College of Life Sciences, Tarim University, Alar, China
| | - Yu Wan
- Key Laboratory of Protection & Utilization of Biological Resources in Tarim Basin, College of Life Sciences, Tarim University, Alar, China
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6
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Pincha N, Marangoni P, Haque A, Klein OD. Parallels in signaling between development and regeneration in ectodermal organs. Curr Top Dev Biol 2022; 149:373-419. [PMID: 35606061 PMCID: PMC10049776 DOI: 10.1016/bs.ctdb.2022.02.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Ectodermal organs originate from the outermost germ layer of the developing embryo and include the skin, hair, tooth, nails, and exocrine glands. These organs develop through tightly regulated, sequential and reciprocal epithelial-mesenchymal crosstalk, and they eventually assume various morphologies and functions while retaining the ability to regenerate. As with many other tissues in the body, the development and morphogenesis of these organs are regulated by a set of common signaling pathways, such as Shh, Wnt, Bmp, Notch, Tgf-β, and Eda. However, subtle differences in the temporal activation, the multiple possible combinations of ligand-receptor activation, the various cofactors, as well as the underlying epigenetic modulation determine how each organ develops into its adult form. Although each organ has been studied separately in considerable detail, the mechanisms underlying the parallels and differences in signaling that regulate their development have rarely been investigated. First, we will use the tooth, the hair follicle, and the mammary gland as representative ectodermal organs to explore how the development of signaling centers and establishment of stem cell populations influence overall growth and morphogenesis. Then we will compare how some of the major signaling pathways (Shh, Wnt, Notch and Yap/Taz) differentially regulate developmental events. Finally, we will discuss how signaling regulates regenerative processes in all three.
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Affiliation(s)
- Neha Pincha
- Program in Craniofacial Biology and Department of Orofacial Sciences, University of California, San Francisco, CA, United States
| | - Pauline Marangoni
- Program in Craniofacial Biology and Department of Orofacial Sciences, University of California, San Francisco, CA, United States
| | - Ameera Haque
- Program in Craniofacial Biology and Department of Orofacial Sciences, University of California, San Francisco, CA, United States
| | - Ophir D Klein
- Program in Craniofacial Biology and Department of Orofacial Sciences, University of California, San Francisco, CA, United States; Department of Pediatrics and Institute for Human Genetics, University of California, San Francisco, CA, United States.
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7
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Kim CF, Jou D, Ganor O, Boskey ER, Kozakewich H, Vargas SO. Prostatic metaplasia and pilar differentiation in gender-affirming mastectomy specimens. Mod Pathol 2022; 35:386-395. [PMID: 34689157 DOI: 10.1038/s41379-021-00951-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 09/30/2021] [Accepted: 10/01/2021] [Indexed: 12/18/2022]
Abstract
With the increasing practice of gender-affirming mastectomy as a therapeutic procedure in the setting of gender dysphoria, there has come a profusion of literature on the pathologic findings within these specimens. Findings reported in over 1500 patients have not included either prostatic metaplasia or pilar metaplasia of breast epithelium. We encountered both of these findings in the course of routine surgical pathology practice and therefore aimed to analyze these index cases together with a retrospective cohort to determine the prevalence, anatomic distribution, pathologic features, and associated clinical findings of prostatic metaplasia and pilar metaplasia in the setting of gender-affirming mastectomy. In addition to the 2 index cases, 20 additional archival gender-affirming mastectomy specimens were studied. Before mastectomies, all but 1 patient received testosterone cypionate, 6/22 patients received norethindrone, and 21/22 practiced breast binding. Prostatic metaplasia, characterized by glandular proliferation along the basal layer of epithelium in breast ducts, and in one case, within lobules, was seen in 18/22 specimens; 4/22 showed pilar metaplasia, consisting of hair shafts located within breast ducts, associated with squamoid metaplasia resembling hair matriceal differentiation. By immunohistochemistry, prostatic metaplasia was positive for PSA in 16/20 cases and positive for NKX3.1 in 15/20 cases. Forty-three reduction mammoplasty control cases showed no pilar metaplasia and no definite prostatic metaplasia, with no PSA and NKX3.1 staining observed. We demonstrate that prostatic metaplasia and pilar metaplasia are strikingly common findings in specimens from female-assigned-at-birth transgender patients undergoing gender-affirming mastectomy. Awareness of these novel entities in the breast is important, to distinguish them from other breast epithelial proliferations and to facilitate accrual of follow-up data for better understanding their natural history.
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Affiliation(s)
- Charlotte F Kim
- Department of Pathology, Boston Children's Hospital, Boston, MA, USA.,Department of Pathology and Immunology, Baylor College of Medicine and Pavilion for Women at Texas Children's Hospital, Houston, TX, USA
| | - David Jou
- Department of Pathology, Boston Children's Hospital, Boston, MA, USA.,Department of Pathology, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Oren Ganor
- Department of Plastic and Oral Surgery, Boston Children's Hospital, Boston, MA, USA
| | - Elizabeth R Boskey
- Department of Plastic and Oral Surgery, Boston Children's Hospital, Boston, MA, USA
| | - Harry Kozakewich
- Department of Pathology, Boston Children's Hospital, Boston, MA, USA
| | - Sara O Vargas
- Department of Pathology, Boston Children's Hospital, Boston, MA, USA.
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8
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Pedersen EB, Christiansen S, Svingen T. AOP key event relationship report: Linking androgen receptor antagonism with nipple retention. Curr Res Toxicol 2022; 3:100085. [PMID: 36090961 PMCID: PMC9459418 DOI: 10.1016/j.crtox.2022.100085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 08/25/2022] [Accepted: 08/25/2022] [Indexed: 12/01/2022] Open
Abstract
A full AOP KER description linking AR antagonism with nipple retention in rodents. Described KER 2133 is a non-adjacent KER of an intended AOP delineating anti-androgenicity as a mode for nipple retention. A case study for developing and publishing independent units of information under the AOP framework.
In rat developmental and reproductive toxicity studies, nipple/areola retention (NR) in male offspring is a biomarker for reduced androgen signaling during development. This is because nipples normally regress in male rats in response to androgen signaling during critical stages of development. NR is thus included as a mandatory endpoint in several OECD test guidelines for assessment of chemicals, particularly as a readout for anti-androgenic effects relevant for reproductive toxicity. With the growing interest in developing Adverse Outcome Pathways (AOPs) to aid in chemical risk assessment, a more pragmatic approach has been proposed, whereby essential units of knowledge could be developed independently of complete AOPs, not least emergent key event relationships (KERs). Herein, we have developed a KER linking “androgen receptor antagonism” and “increased areola/nipple retention”. The KER is based on a literature review conducted in a transparent semi-systematic manner in peer-reviewed databases with pre-defined inclusion criteria. Twenty-seven papers were included for development of the KER. The results support a qualitative relationship between the two key events (KEs) with a high weight of evidence; i.e., a causal relationship between androgen receptor (AR) antagonism and nipple retention in male rats exists.
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9
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Abstract
Fluid secretion by exocrine glandular organs is essential to the survival of mammals. Each glandular unit within the body is uniquely organized to carry out its own specific functions, with failure to establish these specialized structures resulting in impaired organ function. Here, we review glandular organs in terms of shared and divergent architecture. We first describe the structural organization of the diverse glandular secretory units (the end-pieces) and their fluid transporting systems (the ducts) within the mammalian system, focusing on how tissue architecture corresponds to functional output. We then highlight how defects in development of end-piece and ductal architecture impacts secretory function. Finally, we discuss how knowledge of exocrine gland structure-function relationships can be applied to the development of new diagnostics, regenerative approaches and tissue regeneration.
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Affiliation(s)
- Sameed Khan
- Department of Obstetrics Gynecology and Reproductive Biology, Michigan State University, East Lansing, MI 48824, USA
- Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI 48824, USA
| | - Sarah Fitch
- Department of Obstetrics Gynecology and Reproductive Biology, Michigan State University, East Lansing, MI 48824, USA
- Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI 48824, USA
| | - Sarah Knox
- Department of Cell and Tissue Biology, University of California, San Francisco, CA 94143, USA
| | - Ripla Arora
- Department of Obstetrics Gynecology and Reproductive Biology, Michigan State University, East Lansing, MI 48824, USA
- Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI 48824, USA
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10
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Schwartz CL, Christiansen S, Hass U, Ramhøj L, Axelstad M, Löbl NM, Svingen T. On the Use and Interpretation of Areola/Nipple Retention as a Biomarker for Anti-androgenic Effects in Rat Toxicity Studies. FRONTIERS IN TOXICOLOGY 2021; 3:730752. [PMID: 35295101 PMCID: PMC8915873 DOI: 10.3389/ftox.2021.730752] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 10/13/2021] [Indexed: 11/13/2022] Open
Abstract
Areola/nipple retention (NR) is an established biomarker for an anti-androgenic mode of action in rat toxicity studies. It is a mandatory measurement under several OECD test guidelines and is typically assessed in combination with anogenital distance (AGD). Both NR and AGD are considered retrospective biomarkers of insufficient androgen signaling during the masculinization programming window in male fetuses. However, there are still aspects concerning NR as a biomarker for endocrine disruption that remains to be clarified. For instance, can NR be regarded a permanent adverse effect? Is it a redundant measurement if AGD is assessed in the same study? Is NR equally sensitive and specific to anti-androgenic chemical substances as a shortening of male AGD? In this review we discuss these and other aspects concerning the use of NR as a biomarker in toxicity studies. We have collected available literature from rat toxicity studies that have reported on NR and synthesized the data in order to draw a clearer picture about the sensitivity and specificity of NR as an effect biomarker for an anti-androgenic mode of action, including comparisons to AGD measurements. We carefully conclude that NR and AGD in rats for the most part display similar sensitivity and specificity, but that there are clear exceptions which support the continued assessment of both endpoints in relevant reproductive toxicity studies. Available literature also support the view that NR in infant male rats signifies a high risk for permanent nipples in adulthood. Finally, the literature suggests that the mechanisms of action leading from a chemical stressor event to either NR or short AGD in male offspring are overlapping with respect to canonical androgen signaling, yet differ with respect to other mechanisms of action.
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11
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Repeated mutation of a developmental enhancer contributed to human thermoregulatory evolution. Proc Natl Acad Sci U S A 2021; 118:2021722118. [PMID: 33850016 PMCID: PMC8072367 DOI: 10.1073/pnas.2021722118] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Humans sweat to cool their bodies and have by far the highest eccrine sweat gland density among primates. Humans' high eccrine gland density has long been recognized as a hallmark human evolutionary adaptation, but its genetic basis has been unknown. In humans, expression of the Engrailed 1 (EN1) transcription factor correlates with the onset of eccrine gland formation. In mice, regulation of ectodermal En1 expression is a major determinant of natural variation in eccrine gland density between strains, and increased En1 expression promotes the specification of more eccrine glands. Here, we show that regulation of EN1 has evolved specifically on the human lineage to promote eccrine gland formation. Using comparative genomics and validation of ectodermal enhancer activity in mice, we identified a human EN1 skin enhancer, hECE18. We showed that multiple epistatically interacting derived substitutions in the human ECE18 enhancer increased its activity compared with nonhuman ape orthologs in cultured keratinocytes. Repression of hECE18 in human cultured keratinocytes specifically attenuated EN1 expression, indicating this element positively regulates EN1 in this context. In a humanized enhancer knock-in mouse, hECE18 increased developmental En1 expression in the skin to induce the formation of more eccrine glands. Our study uncovers a genetic basis contributing to the evolution of one of the most singular human adaptations and implicates multiple interacting mutations in a single enhancer as a mechanism for human evolutionary change.
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12
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Li S, Zheng X, Nie Y, Chen W, Liu Z, Tao Y, Hu X, Hu Y, Qiao H, Qi Q, Pei Q, Cai D, Yu M, Mou C. Defining Key Genes Regulating Morphogenesis of Apocrine Sweat Gland in Sheepskin. Front Genet 2019; 9:739. [PMID: 30761184 PMCID: PMC6363705 DOI: 10.3389/fgene.2018.00739] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Accepted: 12/22/2018] [Indexed: 01/04/2023] Open
Abstract
The apocrine sweat gland is a unique skin appendage in humans compared to mouse and chicken models. The absence of apocrine sweat glands in chicken and murine skin largely restrains further understanding of the complexity of human skin biology and skin diseases, like hircismus. Sheep may serve as an additional system for skin appendage investigation owing to the distributions and histological similarities between the apocrine sweat glands of sheep trunk skin and human armpit skin. To understand the molecular mechanisms underlying morphogenesis of apocrine sweat glands in sheepskin, transcriptome analyses were conducted to reveal 1631 differentially expressed genes that were mainly enriched in three functional groups (cellular component, molecular function and biological process), particularly in gland, epithelial, hair follicle and skin development. There were 7 Gene Ontology (GO) terms enriched in epithelial cell migration and morphogenesis of branching epithelium that were potentially correlated with the wool follicle peg elongation. An additional 5 GO terms were enriched in gland morphogenesis (20 genes), gland development (42 genes), salivary gland morphogenesis and development (8 genes), branching involved in salivary gland morphogenesis (6 genes) and mammary gland epithelial cell differentiation (4 genes). The enriched gland-related genes and two Kyoto Encyclopedia of Genes and Genomes pathway genes (WNT and TGF-β) were potentially involved in the induction of apocrine sweat glands. Genes named BMPR1A, BMP7, SMAD4, TGFB3, WIF1, and WNT10B were selected to validate transcript expression by qRT-PCR. Immunohistochemistry was performed to localize markers for hair follicle (SOX2), skin fibroblast (PDGFRB), stem cells (SOX9) and BMP signaling (SMAD5) in sheepskin. SOX2 and PDGFRB were absent in apocrine sweat glands. SOX9 and SMAD5 were both observed in precursor cells of apocrine sweat glands and later in gland ducts. These results combined with the upregulation of BMP signaling genes indicate that apocrine sweat glands were originated from outer root sheath of primary wool follicle and positively regulated by BMP signaling. This report established the primary network regulating early development of apocrine sweat glands in sheepskin and will facilitate the further understanding of histology and pathology of apocrine sweat glands in human and companion animal skin.
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Affiliation(s)
- Shaomei Li
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Xinting Zheng
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Yangfan Nie
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Wenshuo Chen
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Zhiwei Liu
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Yingfeng Tao
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Xuewen Hu
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Yong Hu
- Qinghai Academy of Animal Science and Veterinary Medicine, Xining, China
| | - Haisheng Qiao
- Qinghai Academy of Animal Science and Veterinary Medicine, Xining, China
| | - Quanqing Qi
- Sanjiaocheng Sheep Breeding Farm, Haibei, China
| | | | - Danzhuoma Cai
- Animal Husbandry and Veterinary Station, Haixi, China
| | - Mei Yu
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Chunyan Mou
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
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13
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Sterbing SJ, Moss CF. Comparative analysis of the distribution and morphology of tactile hairs on the wing membrane of four bat species. J Mammal 2017. [DOI: 10.1093/jmammal/gyx146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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14
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Dhouailly D, Godefroit P, Martin T, Nonchev S, Caraguel F, Oftedal O. Getting to the root of scales, feather and hair: As deep as odontodes? Exp Dermatol 2017; 28:503-508. [DOI: 10.1111/exd.13391] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/30/2017] [Indexed: 12/26/2022]
Affiliation(s)
- Danielle Dhouailly
- Department of Biology and ChemistryUniversité Grenoble‐Alpes La Tronche France
| | - Pascal Godefroit
- Directorate “Earth and History of Life” Royal Belgian Institute of Natural Sciences Bruxelles Belgium
| | - Thomas Martin
- Steinmann‐Institut für GeologieMineralogie und PaläontologieUniversität Bonn Bonn Germany
| | - Stefan Nonchev
- INSERM, U823Institute for Advanced BiosciencesUniversité Grenoble‐Alpes Rhône‐Alpes France
| | - Flavien Caraguel
- Department of Biology and ChemistryUniversité Grenoble‐Alpes La Tronche France
| | - Olav Oftedal
- Smithsonian Environmental Research Center Edgewater MD USA
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15
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Lu CP, Polak L, Keyes BE, Fuchs E. Spatiotemporal antagonism in mesenchymal-epithelial signaling in sweat versus hair fate decision. Science 2017; 354:354/6319/aah6102. [PMID: 28008008 DOI: 10.1126/science.aah6102] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 09/16/2016] [Accepted: 11/18/2016] [Indexed: 12/12/2022]
Abstract
The gain of eccrine sweat glands in hairy body skin has empowered humans to run marathons and tolerate temperature extremes. Epithelial-mesenchymal cross-talk is integral to the diverse patterning of skin appendages, but the molecular events underlying their specification remain largely unknown. Using genome-wide analyses and functional studies, we show that sweat glands are specified by mesenchymal-derived bone morphogenetic proteins (BMPs) and fibroblast growth factors that signal to epithelial buds and suppress epithelial-derived sonic hedgehog (SHH) production. Conversely, hair follicles are specified when mesenchymal BMP signaling is blocked, permitting SHH production. Fate determination is confined to a critical developmental window and is regionally specified in mice. In contrast, a shift from hair to gland fates is achieved in humans when a spike in BMP silences SHH during the final embryonic wave(s) of bud morphogenesis.
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Affiliation(s)
- Catherine P Lu
- Laboratory of Mammalian Cell Biology and Development, The Rockefeller University, New York, NY 10065, USA
| | - Lisa Polak
- Laboratory of Mammalian Cell Biology and Development, The Rockefeller University, New York, NY 10065, USA
| | - Brice E Keyes
- Laboratory of Mammalian Cell Biology and Development, The Rockefeller University, New York, NY 10065, USA
| | - Elaine Fuchs
- Laboratory of Mammalian Cell Biology and Development, The Rockefeller University, New York, NY 10065, USA. .,Howard Hughes Medical Institute, Chevy Chase, MD, 20815-6789, USA
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16
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Veltmaat JM. Prenatal Mammary Gland Development in the Mouse: Research Models and Techniques for Its Study from Past to Present. Methods Mol Biol 2017; 1501:21-76. [PMID: 27796947 DOI: 10.1007/978-1-4939-6475-8_2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Mammary gland development starts during prenatal life, when at designated positions along the ventrolateral boundary of the embryonic or fetal trunk, surface ectodermal cells coalesce to form primordia for mammary glands, instead of differentiating into epidermis. With the wealth of genetically engineered mice available as research models, our understanding of the prenatal phase of mammary development has recently greatly advanced. This understanding includes the recognition of molecular and mechanistic parallels between prenatal and postnatal mammary morphogenesis and even tumorigenesis, much of which can moreover be extrapolated to human. This makes the murine embryonic mammary gland a useful model for a myriad of questions pertaining to normal and pathological breast development. Hence, unless indicated otherwise, this review describes embryonic mammary gland development in mouse only, and lists mouse models that have been examined for defects in embryonic mammary development. Techniques that originated in the field of developmental biology, such as explant culture and tissue recombination, were adapted specifically to research on the embryonic mammary gland. Detailed protocols for these techniques have recently been published elsewhere. This review describes how the development and adaptation of these techniques moved the field forward from insights on (comparative) morphogenesis of the embryonic mammary gland to the understanding of tissue and molecular interactions and their regulation of morphogenesis and functional development of the embryonic mammary gland. It is here furthermore illustrated how generic molecular biology and biochemistry techniques can be combined with these older, developmental biology techniques, to address relevant research questions. As such, this review should provide a solid starting point for those wishing to familiarize themselves with this fascinating and important subdomain of mammary gland biology, and guide them in designing a relevant research strategy.
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Affiliation(s)
- Jacqueline M Veltmaat
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore.
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17
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The Study on Biological Function of Keratin 26, a Novel Member of Liaoning Cashmere Goat Keratin Gene Family. PLoS One 2016; 11:e0168015. [PMID: 27997570 PMCID: PMC5173340 DOI: 10.1371/journal.pone.0168015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 11/25/2016] [Indexed: 11/29/2022] Open
Abstract
In our research, we explored the relationship between Keratin 26 and the regulation of fine hair, BMP signaling pathway, MT, FGF5, and IGF-I. The result of hybridization in situ revealed that Keratin 26 was specially expressed in cortex of skin hair follicles; the result of immunohistochemistry indicated that Keratin 26 was expressed in internal root sheath, external root sheath. Then, Real-time quantitative PCR results showed that relative expressive quantity of Keratin 26 was 1.08 or 3.3 × greater in secondary follicle than primary follicle during anagen or catagen; the difference during anagen was not remarkable (p>0.05), however, that of catagen was extremely significant (p<0.01). Relative expressive quantity of Keratin 26 increased during telogen; the difference was extremely significant (p<0.01). Moreover, after Noggin expression interference using RNAi technology, we found that relative expressive quantity of Keratin 26 extremely remarkably declined (p<0.01); after K26 overexpression, we found that relative expressive quantity of Noggin extremely remarkably increased (p<0.01). We detected expressive quantity change of Keratin 26 and Keratin 26 using Real-time quantitative PCR and immunofluorescence technologies after fibroblasts were treated with MT, FGF5 or IGF-I; the results indicated that MT and FGF5 played a positive role in Keratin 26 and Keratin 26 expression, IGF-I played a negative role in Keratin 26 expression, positive role in Keratin 26 expression. The results above showed that Keratin 26 could inhibit cashmere growth, and was related to entering to catagen and telogen of hair follicles; Keratin 26 and BMP signaling pathway were two antagonistic pathways each other which could inhibit growth and development of cashmere; MT, FGF5 and IGF-I could affect expression of Keratin 26 and Keratin 26, and Keratin 26 was one of the important pathways that MT induced cashmere production in advance, FGF5 regulated cashmere growth and IGF-I promoted cashmere growth and development.
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18
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Sterbing-D'Angelo SJ, Chadha M, Marshall KL, Moss CF. Functional role of airflow-sensing hairs on the bat wing. J Neurophysiol 2016; 117:705-712. [PMID: 27852729 DOI: 10.1152/jn.00261.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 11/15/2016] [Indexed: 11/22/2022] Open
Abstract
The wing membrane of the big brown bat (Eptesicus fuscus) is covered by a sparse grid of microscopic hairs. We showed previously that various tactile receptors (e.g., lanceolate endings and Merkel cell neurite complexes) are associated with wing-hair follicles. Furthermore, we found that depilation of these hairs decreased the maneuverability of bats in flight. In the present study, we investigated whether somatosensory signals arising from the hairs carry information about airflow parameters. Neural responses to calibrated air puffs on the wing were recorded from primary somatosensory cortex of E. fuscus Single units showed sparse, phasic, and consistently timed spikes that were insensitive to air-puff duration and magnitude. The neurons discriminated airflow from different directions, and a majority responded with highest firing rates to reverse airflow from the trailing toward the leading edge of the dorsal wing. Reverse airflow, caused by vortices, occurs commonly in slowly flying bats. Hence, the present findings suggest that cortical neurons are specialized to monitor reverse airflow, indicating laminar airflow disruption (vorticity) that potentially destabilizes flight and leads to stall. NEW & NOTEWORTHY Bat wings are adaptive airfoils that enable demanding flight maneuvers. The bat wing is sparsely covered with sensory hairs, and wing-hair removal results in reduced flight maneuverability. Here, we report for the first time single-neuron responses recorded from primary somatosensory cortex to airflow stimulation that varied in amplitude, duration, and direction. The neurons show high sensitivity to the directionality of airflow and might act as stall detectors.
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Affiliation(s)
- S J Sterbing-D'Angelo
- Institute for Systems Research, University of Maryland, College Park, Maryland; .,Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland; and
| | - M Chadha
- Program in Neuroscience and Cognitive Science, University of Maryland, College Park, Maryland.,Department of Psychology, University of Maryland, College Park, Maryland.,Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland; and
| | - K L Marshall
- Departments of Dermatology and Physiology and Cellular Biophysics, Columbia University, New York, New York
| | - C F Moss
- Institute for Systems Research, University of Maryland, College Park, Maryland.,Program in Neuroscience and Cognitive Science, University of Maryland, College Park, Maryland.,Department of Psychology, University of Maryland, College Park, Maryland.,Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland; and
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19
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Kayserili H, Altunoglu U, Yesil G, Rosti RÖ. Microcephaly, dysmorphic features, corneal dystrophy, hairy nipples, underdeveloped labioscrotal folds, and small cerebellum in four patients. Am J Med Genet A 2016; 170:1391-9. [PMID: 27075597 DOI: 10.1002/ajmg.a.37652] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 03/30/2016] [Indexed: 11/08/2022]
Abstract
Pontocerebellar hypoplasia (PCH) can occur as an isolated entity or part of a syndrome. PCH has been reported with facial dysmorphism, ocular anomalies, and genital anomalies, but the co-occurrence of all four has not been previously described. We report on four patients, born to two consanguineous families that are not related to one another, with distinctive facial features (short forehead, laterally extended, medially flared eyebrows), corneal dystrophy, underdevelopment of labioscrotal folds, and nonprogressive PCH. In addition, the patients show hair extruding from the lactiferous ducts, which to our knowledge has not been described before. The parental consanguinity, affected siblings of both genders, and absent manifestations in parents, indicate an autosomal recessive pattern of inheritance as most likely. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Hülya Kayserili
- Department of Medical Genetics, Koç University, School of Medicine (KUSoM), Istanbul, Turkey.,Department of Medical Genetics, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey
| | - Umut Altunoglu
- Department of Medical Genetics, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey
| | - Gozde Yesil
- Department of Genetics, Bezmialem Vakıf University, School of Medicine, Istanbul, Turkey
| | - Rasim Özgür Rosti
- Department of Medical Genetics, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey.,Department of Neurosciences, Laboratory for Pediatric Brain Diseases, University of California San Diego, La Jolla, California
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20
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Li A, Lai YC, Figueroa S, Yang T, Widelitz RB, Kobielak K, Nie Q, Chuong CM. Deciphering principles of morphogenesis from temporal and spatial patterns on the integument. Dev Dyn 2015; 244:905-20. [PMID: 25858668 PMCID: PMC4520785 DOI: 10.1002/dvdy.24281] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 03/04/2015] [Accepted: 04/03/2015] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND How tissue patterns form in development and regeneration is a fundamental issue remaining to be fully understood. The integument often forms repetitive units in space (periodic patterning) and time (cyclic renewal), such as feathers and hairs. Integument patterns are visible and experimentally manipulatable, helping us reveal pattern formative processes. Variability is seen in regional phenotypic specificities and temporal cycling at different physiological stages. RESULTS Here we show some cellular/molecular bases revealed by analyzing integument patterns. (1) Localized cellular activity (proliferation, rearrangement, apoptosis, differentiation) transforms prototypic organ primordia into specific shapes. Combinatorial positioning of different localized activity zones generates diverse and complex organ forms. (2) Competitive equilibrium between activators and inhibitors regulates stem cells through cyclic quiescence and activation. CONCLUSIONS Dynamic interactions between stem cells and their adjacent niche regulate regenerative behavior, modulated by multi-layers of macro-environmental factors (dermis, body hormone status, and external environment). Genomics studies may reveal how positional information of localized cellular activity is stored. In vivo skin imaging and lineage tracing unveils new insights into stem cell plasticity. Principles of self-assembly obtained from the integumentary organ model can be applied to help restore damaged patterns during regenerative wound healing and for tissue engineering to rebuild tissues. Developmental Dynamics 244:905-920, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Ang Li
- Department of Pathology, University of Southern California, Los Angeles, California
| | - Yung-Chih Lai
- Department of Pathology, University of Southern California, Los Angeles, California
- Center for Developmental Biology and Regenerative Medicine, Taiwan University, Taipei, Taiwan
| | - Seth Figueroa
- Department of Biomedical Engineering, University of California, Irvine, California
| | - Tian Yang
- Department of Cell Biology, College of Basic Medicine, Third Military Medical University, Chongqing, China
| | - Randall B Widelitz
- Department of Pathology, University of Southern California, Los Angeles, California
| | - Krzysztof Kobielak
- Department of Pathology, University of Southern California, Los Angeles, California
| | - Qing Nie
- Department of Mathematics, University of California, Irvine, California
| | - Cheng Ming Chuong
- Department of Pathology, University of Southern California, Los Angeles, California
- Center for Developmental Biology and Regenerative Medicine, Taiwan University, Taipei, Taiwan
- Stem Cell and Regenerative Medicine Center, China Medical University, Taichung, Taiwan
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21
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Marshall KL, Chadha M, deSouza LA, Sterbing-D'Angelo SJ, Moss CF, Lumpkin EA. Somatosensory substrates of flight control in bats. Cell Rep 2015; 11:851-858. [PMID: 25937277 DOI: 10.1016/j.celrep.2015.04.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 03/11/2015] [Accepted: 03/29/2015] [Indexed: 10/23/2022] Open
Abstract
Flight maneuvers require rapid sensory integration to generate adaptive motor output. Bats achieve remarkable agility with modified forelimbs that serve as airfoils while retaining capacity for object manipulation. Wing sensory inputs provide behaviorally relevant information to guide flight; however, components of wing sensory-motor circuits have not been analyzed. Here, we elucidate the organization of wing innervation in an insectivore, the big brown bat, Eptesicus fuscus. We demonstrate that wing sensory innervation differs from other vertebrate forelimbs, revealing a peripheral basis for the atypical topographic organization reported for bat somatosensory nuclei. Furthermore, the wing is innervated by an unusual complement of sensory neurons poised to report airflow and touch. Finally, we report that cortical neurons encode tactile and airflow inputs with sparse activity patterns. Together, our findings identify neural substrates of somatosensation in the bat wing and imply that evolutionary pressures giving rise to mammalian flight led to unusual sensorimotor projections.
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Affiliation(s)
- Kara L Marshall
- Departments of Dermatology and Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Mohit Chadha
- Program in Neuroscience and Cognitive Science, University of Maryland, College Park, MD 20742, USA; Department of Psychology, University of Maryland, College Park, MD 20742, USA
| | - Laura A deSouza
- Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
| | | | - Cynthia F Moss
- Program in Neuroscience and Cognitive Science, University of Maryland, College Park, MD 20742, USA; Department of Psychology, University of Maryland, College Park, MD 20742, USA; Institute for Systems Research, University of Maryland, College Park, MD 20742, USA.
| | - Ellen A Lumpkin
- Departments of Dermatology and Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA.
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22
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Cidea control of lipid storage and secretion in mouse and human sebaceous glands. Mol Cell Biol 2014; 34:1827-38. [PMID: 24636991 DOI: 10.1128/mcb.01723-13] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Sebaceous glands are skin appendages that secrete sebum onto hair follicles to lubricate the hair and maintain skin homeostasis. In this study, we demonstrated that Cidea is expressed at high levels in lipid-laden mature sebocytes and that Cidea deficiency led to dry hair and hair loss in aged mice. In addition, Cidea-deficient mice had markedly reduced levels of skin surface lipids, including triacylglycerides (TAGs) and wax diesters (WDEs), and these mice were defective in water repulsion and thermoregulation. Furthermore, we observed that Cidea-deficient sebocytes accumulated a large number of smaller-sized lipid droplets (LDs), whereas overexpression of Cidea in human SZ95 sebocytes resulted in increased lipid storage and the accumulation of large LDs. Importantly, Cidea was highly expressed in human sebaceous glands, and its expression levels were positively correlated with human sebum secretion. Our data revealed that Cidea is a crucial regulator of sebaceous gland lipid storage and sebum lipid secretion in mammals and humans.
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23
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Lu C, Fuchs E. Sweat gland progenitors in development, homeostasis, and wound repair. Cold Spring Harb Perspect Med 2014; 4:4/2/a015222. [PMID: 24492848 DOI: 10.1101/cshperspect.a015222] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The human body is covered with several million sweat glands. These tiny coiled tubular skin appendages produce the sweat that is our primary source of cooling and hydration of the skin. Numerous studies have been published on their morphology and physiology. Until recently, however, little was known about how glandular skin maintains homeostasis and repairs itself after tissue injury. Here, we provide a brief overview of sweat gland biology, including newly identified reservoirs of stem cells in glandular skin and their activation in response to different types of injuries. Finally, we discuss how the genetics and biology of glandular skin has advanced our knowledge of human disorders associated with altered sweat gland activity.
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Affiliation(s)
- Catherine Lu
- Laboratory of Mammalian Cell Biology and Development, The Rockefeller University, New York, New York 10065
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24
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Chandramouli A, Hatsell SJ, Pinderhughes A, Koetz L, Cowin P. Gli activity is critical at multiple stages of embryonic mammary and nipple development. PLoS One 2013; 8:e79845. [PMID: 24260306 PMCID: PMC3832531 DOI: 10.1371/journal.pone.0079845] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Accepted: 09/24/2013] [Indexed: 01/12/2023] Open
Abstract
Gli3 is a transcriptional regulator of Hedgehog (Hh) signaling that functions as a repressor (Gli3R) or activator (Gli3A) depending upon cellular context. Previously, we have shown that Gli3R is required for the formation of mammary placodes #3 and #5. Here, we report that this early loss of Gli3 results in abnormal patterning of two critical regulators: Bmp4 and Tbx3, within the presumptive mammary rudiment (MR) #3 zone. We also show that Gli3 loss leads to failure to maintain mammary mesenchyme specification and loss of epithelial Wnt signaling, which impairs the later development of remaining MRs: MR#2 showed profound evagination and ectopic hairs formed within the presumptive areola; MR#4 showed mild invagination defects and males showed inappropriate retention of mammary buds in Gli3xt/xt mice. Importantly, mice genetically manipulated to misactivate Hh signaling displayed the same phenotypic spectrum demonstrating that the repressor function of Gli3R is essential during multiple stages of mammary development. In contrast, positive Hh signaling occurs during nipple development in a mesenchymal cuff around the lactiferous duct and in muscle cells of the nipple sphincter. Collectively, these data show that repression of Hh signaling by Gli3R is critical for early placodal patterning and later mammary mesenchyme specification whereas positive Hh signaling occurs during nipple development.
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Affiliation(s)
- Anupama Chandramouli
- Department of Cell Biology, New York University School of Medicine, New York, New York, United States of America
- The Ronald O. Perelman Department of Dermatology, New York University School of Medicine, New York, New York, United States of America
| | - Sarah J. Hatsell
- Department of Cell Biology, New York University School of Medicine, New York, New York, United States of America
- The Ronald O. Perelman Department of Dermatology, New York University School of Medicine, New York, New York, United States of America
| | - Alicia Pinderhughes
- Department of Cell Biology, New York University School of Medicine, New York, New York, United States of America
| | - Lisa Koetz
- Department of Cell Biology, New York University School of Medicine, New York, New York, United States of America
| | - Pamela Cowin
- Department of Cell Biology, New York University School of Medicine, New York, New York, United States of America
- The Ronald O. Perelman Department of Dermatology, New York University School of Medicine, New York, New York, United States of America
- * E-mail:
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25
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Sakakura T, Suzuki Y, Shiurba R. Mammary stroma in development and carcinogenesis. J Mammary Gland Biol Neoplasia 2013; 18:189-97. [PMID: 23604977 DOI: 10.1007/s10911-013-9281-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 04/10/2013] [Indexed: 12/13/2022] Open
Abstract
Mammary glands of adult human females are secretory organs comprised of interdependent epithelial and mesenchymal cells. These cells constitute an assemblage of collecting ducts that end in terminal duct lobular units with hollow alveolar ductules that can differentiate to produce and expel milk. Systemic and maternal hormones, autocrine and paracrine growth factors, and cytokines regulate virtually all phases of mammary gland development. During organogenesis, epithelial and mesenchymal cells interact to form precursors of the parenchyma and stroma in the mature gland. Organogenesis precedes five stages of postnatal development: puberty, pregnancy, lactation, involution, and menopause. Each stage requires a specific set of morphogenetic changes in glandular structure and function. Cycles of cell proliferation, differentiation, and involution may recur until menopause. In addition, physiological responses such as inflammation and pathological events such as tumorigenesis are remarkable for their similarities to embryonic morphogenesis. Here we take a succinct look at the ever-improving understanding of stroma-epithelial interactions and mesenchyme function in mammary gland biology.
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26
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Propper AY, Howard BA, Veltmaat JM. Prenatal morphogenesis of mammary glands in mouse and rabbit. J Mammary Gland Biol Neoplasia 2013; 18:93-104. [PMID: 23736987 PMCID: PMC3691486 DOI: 10.1007/s10911-013-9298-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 05/02/2013] [Indexed: 01/25/2023] Open
Abstract
Our understanding of prenatal morphogenesis of mammary glands has recently greatly advanced. This review focuses on morphogenesis proper, as well as cellular processes and tissue interactions involved in the progression of the embryonic mammary gland through sequential morphogenic stages in both the mouse and rabbit embryo. We provide a synthesis of both historical and more recent studies of embryonic mammary gland development, as well as arguments to revise old concepts about mechanisms of mammary line and rudiment formation. Finally, we highlight outstanding issues that remain to be addressed.
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Affiliation(s)
- Alain Y. Propper
- Laboratoire de Neurosciences, EA481, Université de Franche-Comté, (Emeritus), 25030 Besançon Cedex, France
| | - Beatrice A. Howard
- Division of Breast Cancer Research, Breakthrough Breast Cancer Research Centre, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB UK
| | - Jacqueline M. Veltmaat
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), 61 Biopolis Drive, Singapore, 138673 Singapore
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27
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Oftedal OT, Dhouailly D. Evo-devo of the mammary gland. J Mammary Gland Biol Neoplasia 2013; 18:105-20. [PMID: 23681303 DOI: 10.1007/s10911-013-9290-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 04/30/2013] [Indexed: 10/26/2022] Open
Abstract
We propose a new scenario for mammary evolution based on comparative review of early mammary development among mammals. Mammary development proceeds through homologous phases across taxa, but evolutionary modifications in early development produce different final morphologies. In monotremes, the mammary placode spreads out to form a plate-like mammary bulb from which more than 100 primary sprouts descend into mesenchyme. At their distal ends, secondary sprouts develop, including pilosebaceous anlagen, resulting in a mature structure in which mammary lobules and sebaceous glands empty into the infundibula of hair follicles; these structural triads (mammolobular-pilo-sebaceous units or MPSUs) represent an ancestral condition. In marsupials a flask-like mammary bulb elongates as a sprout, but then hollows out; its secondary sprouts include hair and sebaceous anlagen (MPSUs), but the hairs are shed during nipple formation. In some eutherians (cat, horse, human) MPSUs form at the distal ends of primary sprouts; pilosebaceous components either regress or develop into mature structures. We propose that a preexisting structural triad (the apocrine-pilo-sebaceous unit) was incorporated into the evolving mammary structure, and coupled to additional developmental processes that form the mammary line, placode, bulb and primary sprout. In this scenario only mammary ductal trees and secretory tissue derive from ancestral apocrine-like glands. The mammary gland appears to have coopted signaling pathways and genes for secretory products from even earlier integumentary structures, such as odontode (tooth-like) or odontode-derived structures. We speculate that modifications in signal use (such as PTHrP and BMP4) may contribute to taxonomic differences in MPSU development.
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Affiliation(s)
- Olav T Oftedal
- Smithsonian Environmental Research Center, Edgewater, MD 21037, USA.
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28
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Koyama S, Wu HJ, Easwaran T, Thopady S, Foley J. The nipple: a simple intersection of mammary gland and integument, but focal point of organ function. J Mammary Gland Biol Neoplasia 2013; 18:121-31. [PMID: 23674217 DOI: 10.1007/s10911-013-9289-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Accepted: 04/29/2013] [Indexed: 10/26/2022] Open
Abstract
Having glands that secrete milk to nourish neonatal offspring characterizes all mammals. We provide a brief overview of the development and anatomy of nipples and mammary glands in monotremes, marsupials, and marine mammals, and focus on the nipples and mammary glands in terrestrial eutherian species. We first classify eutherians into three groups: the altricial, precocial, and arboreal types based on their rearing system. We then summarize the physiology of lactation and the cell biology of nipples with specific focus on comparing these in the mouse, cow, and human, which represent the three different groups. Finally we propose that the nipple is an example of specialized epidermis. As specialized epidermis, it is dependent the underlying stroma for development and maintenance in adult life. The development of the nipple and signaling pathways that regulate its formation are described.
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Affiliation(s)
- Sachiko Koyama
- Medical Sciences, Indiana University School of Medicine, Jordan Hall, Bloomington, IN 47405, USA
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Hieda K, Hayashi S, Kim JH, Murakami G, Cho BH, Matsubara A. Spatial relationship between expression of cytokeratin-19 and that of connexin-43 in human fetal kidney. Anat Cell Biol 2013; 46:32-8. [PMID: 23560234 PMCID: PMC3615610 DOI: 10.5115/acb.2013.46.1.32] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 02/04/2013] [Accepted: 02/04/2013] [Indexed: 11/27/2022] Open
Abstract
Connexin-43, a major gap junction protein, and cytokeratin-19, one of the intermediate filament keratins, are known to be markers of well-differentiated epithelium. In this study, we investigated the expression of these markers in the head region, lungs, and abdominal organs of 10 human mid-term fetuses. The expression of connexin-43 was found to be restricted to the dura mater, kidney, and adrenal cortex. In the kidney, we found a clear site-dependent difference in the expression pattern of these markers: connexin-43 expression was observed in the tubules of the renal cortex whereas cytokeratin-19 was strongly expressed in the collecting ducts and renal pelvis. This difference remained unchanged throughout the fetal stages examined. Immunoreactivity was not observed for either of the markers in the intrarenal vessels, including the glomeruli, and mesangial cells. Connexin-43 expression seemed to be restricted to the metanephric vesicle-derived structures that differentiate in the urogenital ridge of the splanchnic mesoderm. The adrenal cortex also originates from the same para-aortic mesoderm. In contrast, in the urogenital organs, cytokeratin-19 seemed to be expressed in ducts derived from the urogenital sinus.
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Affiliation(s)
- Keisuke Hieda
- Department of Urology, Hiroshima University School of Medicine, Hiroshima, Japan
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Abstract
Lactation represents an important element of the life history strategies of all mammals, whether monotreme, marsupial, or eutherian. Milk originated as a glandular skin secretion in synapsids (the lineage ancestral to mammals), perhaps as early as the Pennsylvanian period, that is, approximately 310 million years ago (mya). Early synapsids laid eggs with parchment-like shells intolerant of desiccation and apparently dependent on glandular skin secretions for moisture. Mammary glands probably evolved from apocrine-like glands that combined multiple modes of secretion and developed in association with hair follicles. Comparative analyses of the evolutionary origin of milk constituents support a scenario in which these secretions evolved into a nutrient-rich milk long before mammals arose. A variety of antimicrobial and secretory constituents were co-opted into novel roles related to nutrition of the young. Secretory calcium-binding phosphoproteins may originally have had a role in calcium delivery to eggs; however, by evolving into large, complex casein micelles, they took on an important role in transport of amino acids, calcium and phosphorus. Several proteins involved in immunity, including an ancestral butyrophilin and xanthine oxidoreductase, were incorporated into a novel membrane-bound lipid droplet (the milk fat globule) that became a primary mode of energy transfer. An ancestral c-lysozyme lost its lytic functions in favor of a role as α-lactalbumin, which modifies a galactosyltransferase to recognize glucose as an acceptor, leading to the synthesis of novel milk sugars, of which free oligosaccharides may have predated free lactose. An ancestral lipocalin and an ancestral whey acidic protein four-disulphide core protein apparently lost their original transport and antimicrobial functions when they became the whey proteins β-lactoglobulin and whey acidic protein, which with α-lactalbumin provide limiting sulfur amino acids to the young. By the late Triassic period (ca 210 mya), mammaliaforms (mammalian ancestors) were endothermic (requiring fluid to replace incubatory water losses of eggs), very small in size (making large eggs impossible), and had rapid growth and limited tooth replacement (indicating delayed onset of feeding and reliance on milk). Thus, milk had already supplanted egg yolk as the primary nutrient source, and by the Jurassic period (ca 170 mya) vitellogenin genes were being lost. All primary milk constituents evolved before the appearance of mammals, and some constituents may have origins that predate the split of the synapsids from sauropsids (the lineage leading to 'reptiles' and birds). Thus, the modern dairy industry is built upon a very old foundation, the cornerstones of which were laid even before dinosaurs ruled the earth in the Jurassic and Cretaceous periods.
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ALIBARDI LORENZO. Perspectives on Hair Evolution Based on Some Comparative Studies on Vertebrate Cornification. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2012; 318:325-43. [DOI: 10.1002/jez.b.22447] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- LORENZO ALIBARDI
- Comparative Histolab and Dipartimento di Biologia; University of Bologna, Bologna; Italy
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Närhi K, Tummers M, Ahtiainen L, Itoh N, Thesleff I, Mikkola ML. Sostdc1 defines the size and number of skin appendage placodes. Dev Biol 2012; 364:149-61. [PMID: 22509524 DOI: 10.1016/j.ydbio.2012.01.026] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Mammary glands and hair follicles develop as ectodermal organs sharing common features during embryonic morphogenesis. The molecular signals controlling the initiation and patterning of skin appendages involve the bone morphogenetic proteins and Wnt family members, which are commonly thought to serve as inhibitory and activating cues, respectively. Here, we have examined the role of the Bmp and Wnt pathway modulator Sostdc1 in mammary gland, and hair and vibrissa follicle development using Sostdc1-null mice. Contrary to previous speculations, loss of Sostdc1 did not affect pelage hair cycling. Instead, we found that Sostdc1 limits the number of developing vibrissae and other muzzle hair follicles, and the size of primary hair placodes. Sostdc1 controls also the size and shape of mammary buds. Furthermore, Sostdc1 is essential for suppression of hair follicle fate in the normally hairless nipple epidermis, but its loss also promotes the appearance of supernumerary nipple-like protrusions. Our data suggest that functions of Sostdc1 can be largely attributed to its ability to attenuate Wnt/β-catenin signaling.
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Affiliation(s)
- Katja Närhi
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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Jiménez-Rojo L, Granchi Z, Graf D, Mitsiadis TA. Stem Cell Fate Determination during Development and Regeneration of Ectodermal Organs. Front Physiol 2012; 3:107. [PMID: 22539926 PMCID: PMC3336109 DOI: 10.3389/fphys.2012.00107] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 04/03/2012] [Indexed: 12/17/2022] Open
Abstract
The development of ectoderm-derived appendages results in a large variety of highly specialized organs such as hair follicles, mammary glands, salivary glands, and teeth. Despite varying in number, shape, and function, all these ectodermal organs develop through continuous and reciprocal epithelial-mesenchymal interactions, sharing common morphological and molecular features especially during their embryonic development. Diseases such as ectodermal dysplasias can affect simultaneously these organs, suggesting that they may arise from common multipotent precursors residing in the embryonic ectoderm. During embryogenesis, these putative ectodermal stem cells may adopt different fates and consequently be able to generate a variety of tissue-specific stem cells, which are the sources for the various cell lineages that form the diverse organs. The specification of those common epithelial precursors, as well as their further lineage commitment to tissue-specific stem cells, might be controlled by specific signals. It has been well documented that Notch, Wnt, bone morphogenetic protein, and fibroblast growth factor signaling pathways regulate cell fate decisions during the various stages of ectodermal organ development. However, the in vivo spatial and temporal dynamics of these signaling pathways are not yet well understood. Improving the current knowledge on the mechanisms involved in stem cell fate determination during organogenesis and homeostasis of ectodermal organs is crucial to develop effective stem cell-based therapies in order to regenerate or replace pathological and damaged tissues.
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Affiliation(s)
- Lucía Jiménez-Rojo
- Institute of Oral Biology, Zentrum für Zahnmedizin, Faculty of Medicine, University of Zurich Zurich, Switzerland
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Disruption of bone morphogenetic protein receptor 2 (BMPR2) in mammary tumors promotes metastases through cell autonomous and paracrine mediators. Proc Natl Acad Sci U S A 2011; 109:2814-9. [PMID: 21576484 DOI: 10.1073/pnas.1101139108] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Bone morphogenetic proteins (BMPs) are members of the TGF-β superfamily of signaling molecules. BMPs can elicit a wide range of effects in many cell types and have previously been shown to induce growth inhibition in carcinoma cells as well as normal epithelia. Recently, it has been demonstrated that BMP4 and BMP7 are overexpressed in human breast cancers and may have tumor suppressive and promoting effects. We sought to determine whether disruption of the BMP receptor 2 (BMPR2) would alter mammary tumor progression in mice that express the Polyoma middle T antigen. Mice expressing Polyoma middle T antigen under the mouse mammary tumor virus promoter were combined with mice that have doxycycline-inducible expression of a dominant-negative (DN) BMPR2. We did not observe any differences in tumor latency. However, mice expressing the BMPR2-DN had a fivefold increase in lung metastases. We characterized several cell autonomous changes and found that BMPR2-DN-expressing tumor cells had higher rates of proliferation. We also identified unique changes in inflammatory cells and secreted chemokines/cytokines that accompanied BMPR2-DN-expressing tumors. By immunohistochemistry, it was found that BMPR2-DN primary tumors and metastases had an altered reactive stroma, indicating specific changes in the tumor microenvironment. Among the changes we discovered were increased myeloid derived suppressor cells and the chemokine CCL9. BMP was shown to directly regulate CCL9 expression. We conclude that BMPR2 has tumor-suppressive function in mammary epithelia and microenvironment and that disruption can accelerate mammary carcinoma metastases.
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Hughes MW, Wu P, Jiang TX, Lin SJ, Dong CY, Li A, Hsieh FJ, Widelitz RB, Chuong CM. In search of the Golden Fleece: unraveling principles of morphogenesis by studying the integrative biology of skin appendages. Integr Biol (Camb) 2011; 3:388-407. [PMID: 21437328 DOI: 10.1039/c0ib00108b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The mythological story of the Golden Fleece symbolizes the magical regenerative power of skin appendages. Similar to the adventurous pursuit of the Golden Fleece by the multi-talented Argonauts, today we also need an integrated multi-disciplined approach to understand the cellular and molecular processes during development, regeneration and evolution of skin appendages. To this end, we have explored several aspects of skin appendage biology that contribute to the Turing activator/inhibitor model in feather pattern formation, the topo-biological arrangement of stem cells in organ shape determination, the macro-environmental regulation of stem cells in regenerative hair waves, and potential novel molecular pathways in the morphological evolution of feathers. Here we show our current integrative biology efforts to unravel the complex cellular behavior in patterning stem cells and the control of regional specificity in skin appendages. We use feather/scale tissue recombination to demonstrate the timing control of competence and inducibility. Feathers from different body regions are used to study skin regional specificity. Bioinformatic analyses of transcriptome microarrays show the potential involvement of candidate molecular pathways. We further show Hox genes exhibit some region specific expression patterns. To visualize real time events, we applied time-lapse movies, confocal microscopy and multiphoton microscopy to analyze the morphogenesis of cultured embryonic chicken skin explants. These modern imaging technologies reveal unexpectedly complex cellular flow and organization of extracellular matrix molecules in three dimensions. While these approaches are in preliminary stages, this perspective highlights the challenges we face and new integrative tools we will use. Future work will follow these leads to develop a systems biology view and understanding in the morphogenetic principles that govern the development and regeneration of ectodermal organs.
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Affiliation(s)
- Michael W Hughes
- Department of Pathology, School of Medicine, University of Southern California, HMR 315B, 2011 Zonal Ave., Los Angeles, CA 90033, USA
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Abstract
In zoology it is well known that birds are characterized by the presence of feathers, and mammals by hairs. Another common point of view is that avian scales are directly related to reptilian scales. As a skin embryologist, I have been fascinated by the problem of regionalization of skin appendages in amniotes throughout my scientific life. Here I have collected the arguments that result from classical experimental embryology, from the modern molecular biology era, and from the recent discovery of new fossils. These arguments shape my view that avian ectoderm is primarily programmed toward forming feathers, and mammalian ectoderm toward forming hairs. The other ectoderm derivatives - scales in birds, glands in mammals, or cornea in both classes - can become feathers or hairs through metaplastic process, and appear to have a negative regulatory mechanism over this basic program. How this program is altered remains, in most part, to be determined. However, it is clear that the regulation of the Wnt/beta-catenin pathway is a critical hub. The level of beta-catenin is crucial for feather and hair formation, as its down-regulation appears to be linked with the formation of avian scales in chick, and cutaneous glands in mice. Furthermore, its inhibition leads to the formation of nude skin and is required for that of corneal epithelium. Here I propose a new theory, to be further considered and tested when we have new information from genomic studies. With this theory, I suggest that the alpha-keratinized hairs from living synapsids may have evolved from the hypothetical glandular integument of the first amniotes, which may have presented similarities with common day terrestrial amphibians. Concerning feathers, they may have evolved independently of squamate scales, each originating from the hypothetical roughened beta-keratinized integument of the first sauropsids. The avian overlapping scales, which cover the feet in some bird species, may have developed later in evolution, being secondarily derived from feathers.
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Affiliation(s)
- Danielle Dhouailly
- Equipe Ontogenèse et Cellules Souches du Tégument, Centre de Recherche INSERM UJF - U, Institut Albert Bonniot, Site Santé- La Tronche, Grenoble, France.
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