{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,29]],"date-time":"2026-03-29T03:01:21Z","timestamp":1774753281351,"version":"3.50.1"},"reference-count":46,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2025,12,12]],"date-time":"2025-12-12T00:00:00Z","timestamp":1765497600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000069","name":"National Institute of Arthritis and Musculoskeletal and Skin Diseases","doi-asserted-by":"publisher","award":["R37AR047709, RO1AR081322, R01AR076428, P30AR079200"],"award-info":[{"award-number":["R37AR047709, RO1AR081322, R01AR076428, P30AR079200"]}],"id":[{"id":"10.13039\/100000069","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Cells"],"abstract":"<jats:p>Purpose: This study aims to investigate whether two stress keratins, KRT6A or KRT17, label self-renewing stem cells (SCs) in adult mouse Meibomian gland (MG), the palpebral conjunctiva (PC) homeostasis, and to explore the mechanisms regulating their expression. Methods: KRT6A and KRT17 expression in adult mouse MG and PC were examined by single-nucleus RNA sequencing and immunofluorescence (IF). Lineage-tracing experiments were performed using Krt6a-CreERT2 and Krt17-CreERT2 mice carrying the Rosa26RnTnG or Rosa26RmTmG reporter. As Hedgehog (Hh) signaling, the histone deacetylase HDAC3, and the transcription factor KLF4 regulate KRT6A and KRT17 in other contexts, IF was conducted to assess the in vivo effects of overexpression of the Hh pathway activator GLI2\u0394N, and inducible epithelial deletion of Hdac3 or Klf4 on KRT6A and KRT17 expression in the MG and PC. Results: KRT6A and KRT17 are primarily expressed in the MG central duct and ductules. KRT6A also shows robust expression in PC. Lineage tracing indicated that Krt17 labels self-renewing SCs in the MG, whereas Krt6a labels SCs in the PC. GLI2\u0394N overexpression induced ectopic KRT17 expression in MG acini and PC but did not affect KRT6A expression in either MG or PC. Hdac3 deficiency caused expanded expression of KRT6A and KRT17 in MG acini, ectopic KRT17 expression in PC, and increased KRT6A expression in PC basal layer. Klf4 deletion resulted in ectopic KRT17 expression in PC but did not influence KRT6A expression in MG or PC. Conclusions: Krt6a- and Krt17-expressing cells contribute to adult PC and MG homeostasis, respectively. KRT17 expression is enhanced by GLI2\u0394N, and suppressed by HDAC3 and KLF4, whereas KRT6A expression is controlled only by HDAC3. These findings provide important biological insight into tissue-specific maintenance mechanisms and may inform future therapeutic strategies for regenerating MG and PC tissues affected by SC exhaustion or dysregulation.<\/jats:p>","DOI":"10.3390\/cells14241979","type":"journal-article","created":{"date-parts":[[2025,12,12]],"date-time":"2025-12-12T16:19:02Z","timestamp":1765556342000},"page":"1979","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["KRT6A and KRT17 Mark Distinct Stem Cell Populations in the Adult Palpebral Conjunctiva and Meibomian Gland"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1148-4162","authenticated-orcid":false,"given":"Xuming","family":"Zhu","sequence":"first","affiliation":[{"name":"Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"},{"name":"Institute for Regenerative Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"},{"name":"Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mingang","family":"Xu","sequence":"additional","affiliation":[{"name":"Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"},{"name":"Institute for Regenerative Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"},{"name":"Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"David M.","family":"Owens","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Columbia University, New York, NY 10032, USA"},{"name":"Department of Pathology & Cell Biology, Columbia University, New York, NY 10032, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8792-6890","authenticated-orcid":false,"given":"Sarah E.","family":"Millar","sequence":"additional","affiliation":[{"name":"Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"},{"name":"Institute for Regenerative Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"},{"name":"Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"},{"name":"Department of Dermatology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"},{"name":"Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,12,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"108115","DOI":"10.1016\/j.exer.2020.108115","article-title":"Biological functions of tear film","volume":"197","author":"Pflugfelder","year":"2020","journal-title":"Exp. Eye Res."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"109101","DOI":"10.1016\/j.exer.2022.109101","article-title":"Biochemistry of human tear film: A review","volume":"220","author":"Masoudi","year":"2022","journal-title":"Exp. Eye Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1397","DOI":"10.1007\/s40123-023-00669-1","article-title":"Dry Eye Disease Associated with Meibomian Gland Dysfunction: Focus on Tear Film Characteristics and the Therapeutic Landscape","volume":"12","author":"Sheppard","year":"2023","journal-title":"Ophthalmol. Ther."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"731","DOI":"10.1097\/ICO.0000000000000815","article-title":"Epidemiology of Meibomian Gland Dysfunction in an Elderly Population","volume":"35","author":"Alghamdi","year":"2016","journal-title":"Cornea"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1938","DOI":"10.1167\/iovs.10-6997c","article-title":"The international workshop on meibomian gland dysfunction: Report of the subcommittee on anatomy, physiology, and pathophysiology of the meibomian gland","volume":"52","author":"Knop","year":"2011","journal-title":"Investig. Ophthalmol. Vis. Sci."},{"key":"ref_6","unstructured":"Wolff, E., Bron, A.J., Tripathi, R.C., and Tripathi, B.J. (1997). Anatomy of the Eye and Orbit, Chapman & Hall Medical. [8th ed.]."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1186\/s13287-019-1165-5","article-title":"Stem cells: Past, present, and future","volume":"10","author":"Zakrzewski","year":"2019","journal-title":"Stem Cell Res. Ther."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1015","DOI":"10.1146\/annurev-biochem-062917-012341","article-title":"Defining Adult Stem Cells by Function, not by Phenotype","volume":"87","author":"Clevers","year":"2018","journal-title":"Annu. Rev. Biochem."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"399","DOI":"10.1016\/j.stemcr.2016.07.010","article-title":"Renewal of the Holocrine Meibomian Glands by Label-Retaining, Unipotent Epithelial Progenitors","volume":"7","author":"Parfitt","year":"2016","journal-title":"Stem Cell Rep."},{"key":"ref_10","unstructured":"Shumway, C.L., Motlagh, M., and Wade, M. (2024). Anatomy, Head and Neck, Eye Conjunctiva. StatPearls, StatPearls Publishing."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1016\/j.preteyeres.2016.04.005","article-title":"Goblet cells of the conjunctiva: A review of recent findings","volume":"54","author":"Gipson","year":"2016","journal-title":"Prog. Retin. Eye Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1016\/j.jtos.2021.03.003","article-title":"Membrane-associated mucins of the human ocular surface in health and disease","volume":"21","author":"Fini","year":"2021","journal-title":"Ocul. Surf."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"126","DOI":"10.1167\/iovs.04-0356","article-title":"Uniform Distribution of Epithelial Stem Cells in the Bulbar Conjunctiva","volume":"46","author":"Nagasaki","year":"2005","journal-title":"Investig. Ophthalmol. Vis. Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2021","DOI":"10.1167\/iovs.14-16266","article-title":"Human Conjunctival Stem Cells are Predominantly Located in the Medial Canthal and Inferior Forniceal Areas","volume":"56","author":"Stewart","year":"2015","journal-title":"Investig. Ophthalmol. Vis. Sci."},{"key":"ref_15","first-page":"236","article-title":"Label-retaining cells are preferentially located in fornical epithelium: Implications on conjunctival epithelial homeostasis","volume":"36","author":"Wei","year":"1995","journal-title":"Investig. Ophthalmol. Vis. Sci."},{"key":"ref_16","first-page":"301","article-title":"Phorbol ester preferentially stimulates mouse fornical conjunctival and limbal epithelial cells to proliferate in vivo","volume":"39","author":"Lavker","year":"1998","journal-title":"Investig. Ophthalmol. Vis. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"108805","DOI":"10.1016\/j.isci.2024.108805","article-title":"Significance of stress keratin expression in normal and diseased epithelia","volume":"27","author":"Cohen","year":"2024","journal-title":"iScience"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"e1008206","DOI":"10.1371\/journal.ppat.1008206","article-title":"Stress keratin 17 enhances papillomavirus infection-induced disease by downregulating T cell recruitment","volume":"16","author":"Wang","year":"2020","journal-title":"PLoS Pathog."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"363","DOI":"10.1038\/ng0795-363","article-title":"Mutation of a type II keratin gene (K6a) in pachyonychia congenita","volume":"10","author":"Bowden","year":"1995","journal-title":"Nat. Genet."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1038\/ng0395-273","article-title":"Keratin 16 and keratin 17 mutations cause pachyonychia congenita","volume":"9","author":"McLean","year":"1995","journal-title":"Nat. Genet."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"e52712","DOI":"10.7554\/eLife.52712","article-title":"Hair follicle stem cells regulate retinoid metabolism to maintain the self-renewal niche for melanocyte stem cells","volume":"9","author":"Lu","year":"2020","journal-title":"Elife"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1101","DOI":"10.1046\/j.1523-1747.2000.00986.x","article-title":"Keratin 17 Expression in the Hard Epithelial Context of the Hair and Nail, and its Relevance for the Pachyonychia Congenita Phenotype","volume":"114","author":"McGowan","year":"2000","journal-title":"J. Investig. Dermatol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"767","DOI":"10.1046\/j.1365-2133.1998.02499.x","article-title":"Specialized keratin expression pattern in human ridged skin as an adaptation to high physical stress","volume":"139","author":"Swensson","year":"1998","journal-title":"Br. J. Dermatol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"680","DOI":"10.1016\/j.jid.2015.12.021","article-title":"p53 Is a Direct Transcriptional Repressor of Keratin 17: Lessons from a Rat Model of Radiation Dermatitis","volume":"136","author":"Liao","year":"2016","journal-title":"J. Investig. Dermatol."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Zhang, X., Yin, M., and Zhang, L.J. (2019). Keratin 6, 16 and 17-Critical Barrier Alarmin Molecules in Skin Wounds and Psoriasis. Cells, 8.","DOI":"10.3390\/cells8080807"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"752","DOI":"10.2353\/ajpath.2008.071089","article-title":"Hedgehog signaling, keratin 6 induction, and sebaceous gland morphogenesis: Implications for pachyonychia congenita and related conditions","volume":"173","author":"Gu","year":"2008","journal-title":"Am. J. Pathol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2724","DOI":"10.1101\/gad.1221804","article-title":"MIM\/BEG4, a Sonic hedgehog-responsive gene that potentiates Gli-dependent transcription","volume":"18","author":"Callahan","year":"2004","journal-title":"Genes Dev."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"973","DOI":"10.1101\/gad.333674.119","article-title":"HDAC3 ensures stepwise epidermal stratification via NCoR\/SMRT-reliant mechanisms independent of its histone deacetylase activity","volume":"34","author":"Szigety","year":"2020","journal-title":"Genes Dev."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1016\/j.jtos.2024.04.005","article-title":"HDAC1\/2 and HDAC3 play distinct roles in controlling adult Meibomian gland homeostasis","volume":"33","author":"Zhu","year":"2024","journal-title":"Ocul. Surf."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1663","DOI":"10.1038\/s41467-025-56907-6","article-title":"Identification of Meibomian gland stem cell populations and mechanisms of aging","volume":"16","author":"Zhu","year":"2025","journal-title":"Nat. Commun."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1759","DOI":"10.1016\/j.celrep.2013.04.026","article-title":"The touch dome defines an epidermal niche specialized for mechanosensory signaling","volume":"3","author":"Doucet","year":"2013","journal-title":"Cell Rep."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"764","DOI":"10.1523\/JNEUROSCI.5052-10.2011","article-title":"HDAC3 is a critical negative regulator of long-term memory formation","volume":"31","author":"McQuown","year":"2011","journal-title":"J. Neurosci."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"788","DOI":"10.1046\/j.1523-1747.2000.00144.x","article-title":"Conditional gene expression in the epidermis of transgenic mice using the tetracycline-regulated transactivators tTA and rTA linked to the keratin 5 promoter","volume":"115","author":"Diamond","year":"2000","journal-title":"J. Investig. Dermatol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"10482","DOI":"10.1073\/pnas.152238499","article-title":"Early restriction of peripheral and proximal cell lineages during formation of the lung","volume":"99","author":"Perl","year":"2002","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1768","DOI":"10.1172\/JCI46307","article-title":"Basal cell carcinomas in mice arise from hair follicle stem cells and multiple epithelial progenitor populations","volume":"121","author":"Grachtchouk","year":"2011","journal-title":"J. Clin. Investig."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"2619","DOI":"10.1242\/dev.129.11.2619","article-title":"The zinc-finger transcription factor Klf4 is required for terminal differentiation of goblet cells in the colon","volume":"129","author":"Katz","year":"2002","journal-title":"Development"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"8627","DOI":"10.3390\/cimb46080508","article-title":"Keratins 6, 16, and 17 in Health and Disease: A Summary of Recent Findings","volume":"46","author":"Romashin","year":"2024","journal-title":"Curr. Issues Mol. Biol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"F29","DOI":"10.1152\/ajprenal.00538.2014","article-title":"Cutting to the chase: Taking the pulse of label-retaining cells in kidney","volume":"308","author":"Humphreys","year":"2015","journal-title":"Am. J. Physiol. Renal Physiol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/j.jid.2021.05.026","article-title":"HDAC1\/2 Control Proliferation and Survival in Adult Epidermis and Pre\u2013Basal Cell Carcinoma through p16 and p53","volume":"142","author":"Zhu","year":"2022","journal-title":"J. Investig. Dermatol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"999","DOI":"10.1136\/bjophthalmol-2019-314466","article-title":"Histopathology and selective biomarker expression in human meibomian glands","volume":"104","author":"Reneker","year":"2020","journal-title":"Br. J. Ophthalmol."},{"key":"ref_41","first-page":"529","article-title":"Identification of pathogenic genes of pterygium based on the Gene Expression Omnibus database","volume":"12","author":"Yue","year":"2019","journal-title":"Int. J. Ophthalmol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1167\/iovs.66.4.55","article-title":"Expression Distribution of Keratins in Normal and Pathological Corneas and the Regulatory Role of Krt17 on Limbal Stem Cells","volume":"66","author":"Wang","year":"2025","journal-title":"Investig. Ophthalmol. Vis. Sci."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"227","DOI":"10.1016\/j.stem.2023.12.008","article-title":"Human conjunctiva organoids to study ocular surface homeostasis and disease","volume":"31","author":"Korving","year":"2024","journal-title":"Cell Stem Cell"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1248","DOI":"10.1016\/j.stem.2021.04.003","article-title":"Discrete limbal epithelial stem cell populations mediate corneal homeostasis and wound healing","volume":"28","author":"Altshuler","year":"2021","journal-title":"Cell Stem Cell"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"dev197590","DOI":"10.1242\/dev.197590","article-title":"Defining compartmentalized stem cell populations with distinct cell division dynamics in the ocular surface epithelium","volume":"147","author":"Ishii","year":"2020","journal-title":"Development"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"182","DOI":"10.1128\/MCB.00846-06","article-title":"Conditional deletion of the mouse Klf4 gene results in corneal epithelial fragility, stromal edema, and loss of conjunctival goblet cells","volume":"27","author":"Swamynathan","year":"2007","journal-title":"Mol. Cell Biol."}],"container-title":["Cells"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4409\/14\/24\/1979\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,12,16]],"date-time":"2025-12-16T05:15:20Z","timestamp":1765862120000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4409\/14\/24\/1979"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,12,12]]},"references-count":46,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2025,12]]}},"alternative-id":["cells14241979"],"URL":"https:\/\/doi.org\/10.3390\/cells14241979","relation":{},"ISSN":["2073-4409"],"issn-type":[{"value":"2073-4409","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,12,12]]}}}