Dermatology
Abstract
Ceramides are essential skin lipids for maintaining the mammalian skin permeability barrier, which protects against external stimuli. The precursor of epidermal ceramides, glucosylceramides (GlcCer), is synthesized within granular keratinocytes while its precise cellular transport mechanisms remain poorly characterized. Here, we identified three pathogenic variants in the GLTP gene, which encodes glycolipid transfer protein, in five unrelated families with nonsyndromic epidermal differentiation disorder presenting with generalized skin scaling. The biallelic GLTP variants resulted in loss of competent GLTP expression. CRISPR/Cas9-generated Gltp knockout mice exhibited lethal barrier defects, partially recapitulating the clinical features of our patients. We demonstrated that GLTP facilitated GlcCer transport in differentiated keratinocytes, with its deficiency causing impaired GlcCer trafficking and consequent aberrant retention in lysosomes, thereby disrupted lysosome function. The lysosomal dysfunction impaired autophagy flux, resulting in delayed keratinocyte terminal differentiation, which is expected to compromise the skin barrier integrity and ultimate abnormal scaling. Pharmaceutical inhibition of GlcCer synthesis effectively rescued both autophagy and keratinocyte differentiation defects. Our findings establish GLTP as a novel underlying gene for nonsyndromic epidermal differentiation disorders and unravel its essential role in maintaining skin homeostasis during terminal differentiation by mediating epidermal GlcCer transport.
Authors
Zeqiao Zhang, Shimiao Huang, Adam Jackson, Elizabeth A. Jones, Siddharth Banka, Chao Yang, Sisi Zhao, Kunlun Lv, Sha Peng, Zhimiao Lin, Huijun Wang
Abstract
Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by a type 2 immune response that is not fully understood. Single-cell RNA sequencing (scRNA-seq) of human AD skin and murine models of type 2 inflammation identified transcriptionally distinct fibroblast clusters, revealing unique, IL-4Rɑ-dependent populations of immune-acting fibroblasts. These unbiased findings prompted further investigation into the role of dermal fibroblasts during allergic inflammation. These studies demonstrated that, in an inflammatory environment including TNFɑ, IL-1β and IL-17A, IL-4 and IL-13 stimulate both mouse and human fibroblasts to produce multiple chemokines, including Ccl8, which activates Ccr3 to attract T-cells. In the skin, fibroblasts are the primary source of many of these chemokines, and targeted deletion of IL--4rɑ in mouse fibroblasts reduces T-cell infiltration in a mouse model of AD. Additionally, pharmacologic inhibition of Ccr3, the receptor shared by many chemokines produced by fibroblasts, decreases T-cell infiltration and skin inflammation in AD mouse models. These findings demonstrate that dermal fibroblasts are more than passive structural cells; they actively participate in the type 2 immune response and contribute to AD by producing chemokines that increase inflammation. Targeting the functions of immune-acting fibroblasts could offer an alternative therapeutic approach for AD.
Authors
Tomofumi Numata, Michael Shia, Yoshiyuki Nakamura, Fengwu Li, Hung Chan, Teruaki Nakatsuji, Kellen J. Cavagnero, Jared Simmons, Henry Li, Aaroh Anand Joshi, Marta Palomo-Irigoyen, Richard L. Gallo
Abstract
Authors
Ching-Ni Njauw, Zhenyu Ji, David I. Latoni, Jose Mari Villa-Gonzalez, Shelley McCormick, Raj Kumar, Dmitrii Usoltsev, Mykyta Artomov, Boyi Gan, Hensin Tsao
Abstract
Over 15% of cancers worldwide are caused by viruses. Merkel cell polyomavirus (MCPyV) is the most recently discovered human oncovirus and is the only polyomavirus that drives malignant tumors in humans. Here, we show that MCPyV+ Merkel cell carcinoma is defined by neuroendocrine-lineage core regulatory (CR) transcription factors (TFs) (ATOH1, INSM1, ISL1, LHX3, POU4F3, and SOX2) that were essential for tumor survival and that co-bound chromatin with the viral small T antigen at super enhancers. Moreover, MCPyV integration sites were enriched at these neuroendocrine super enhancers. We further discovered that the MCPyV noncoding control region contained a homeodomain binding motif absent in other polyomaviruses that bound ISL1 and LHX3 and depended on them for T antigen expression. To therapeutically target the CR factors, we used histone deacetylase (HDAC) inhibitors to collapse the chromatin architecture and induce topological blurring of superenhancer loops, abrogating core TF expression and halting tumor growth. To our knowledge, our study presents the first example of oncogenic cross-regulation between viral and human epigenomic circuitry to generate interlocking and essential transcriptional feedback circuits that explain why MCPyV causes neuroendocrine cancer and represent a tumor dependency that can be targeted therapeutically.
Authors
Lingling Miao, David Milewski, Amy Coxon, Tara Gelb, Khalid A. Garman, Jadon Porch, Arushi Khanna, Loren Collado, Natasha T. Hill, Kenneth Daily, Serena Vilasi, Danielle Reed, Tiffany Alexander, Gabriel J. Starrett, Maharshi Chakraborty, Young Song, Rachel Choi, Vineela Gangalapudi, Josiah Seaman, Andrew Morton, Klaus J. Busam, Christopher R. Vakoc, Daniel J. Urban, Min Shen, Matthew D. Hall, Richard Sallari, Javed Khan, Berkley E. Gryder, Isaac Brownell
Abstract
The role of CARD9 in the pathogenesis of various chronic fungal infections has been established; however, the precise mechanisms underlying the pathobiology of these infections remain unclear. We aimed to investigate the specific cellular mechanisms by which CARD9 deficiency contributes to the pathogenesis of chronic fungal infections. Using single-cell RNA sequencing (scRNA-seq), we analyzed the immune cell profiles in skin lesions from both murine and human samples. We focused on macrophage differentiation and signaling pathways influenced by CARD9 deficiency. We found that CARD9 deficiency promotes the differentiation of TREM2high macrophages following fungal stimulation, impairing their antifungal functions and inducing exhaustion-like T helper 1 (Th1) cells. Mechanistically, the NF-κB pathway activation was restricted in CARD9-deficient macrophages, leading to enhanced CREB activation, which in turn exerted a positive regulatory effect on Trem2 expression by activating C/EBPβ. Notably, targeting TREM2 enhanced the antifungal immune response in vivo and in vitro, thereby alleviating the severity of CARD9-deficient subcutaneous dematiaceous fungal infection. Our findings highlight the important role of CARD9 in regulating cutaneous antifungal immunity and identify potential targets for immunotherapy in chronic dematiaceous fungal infections.
Authors
Lu Zhang, Zhichun Tang, Yi Zhang, Wenjie Liu, Haitao Jiang, Li Yu, Kexin Lei, Yubo Ma, Yang-xin Fu, Ruoyu Li, Wenyan Wang, Fan Bai, Xiaowen Wang
Abstract
Authors
Kristy Tefft, Amy Wang, Zachary Z. Reinstein, Yue Zhang, Arundhati Pillai, Sunghee Hwang, Spencer Ng, Raymond J. Cho, Jeffrey B. Cheng, Fei Li Kuang, Brett King, Jaehyuk Choi
Abstract
Mechanisms responsible for delayed wound repair are poorly understood despite the common impact of this disorder on health. To study how Staphylococcus aureus disrupts healing, mouse and human wound repair models were evaluated after exposure to S. aureus or commensal Staphylococcus. Quorum sensing by S. aureus, but not S. hominis, delayed repair and inhibited the expression of genes responsible for lipid metabolism in keratinocytes. S. aureus with inactive accessory gene regulator (agr) did not delay healing, and the inhibition of lipid metabolism was recapitulated in vitro by synthetic phenol soluble modulin α1 (psmα1) and psmα4, genes that are under agr control. However, S. aureus strains with single deletion of psmA, psmB, alpha-hemolysin (hla), or hld gene continued to delay repair, suggesting that S. aureus used multiple agr-dependent virulence factors to disrupt healing. These observations provide insight into mechanisms for delayed wound healing, identify quorum sensing as a critical event, and highlight the role of lipid biosynthesis in wound reepithelialization.
Authors
Michelle D. Bagood, Jelena Marjanovic, Nina Jiang, Hung Chan, Tatsuya Dokoshi, Kellen J. Cavagnero, Fengwu Li, Andrea Roso-Mares, Samia Almoughrabie, Edward Liu, Irena Pastar, Marjana Tomic-Canic, Alexander R. Horswill, Richard L. Gallo
Abstract
Few drugs are available for rare diseases due to economic disincentives. However, tailored medications for extremely-rare disorders (N-of-1) offer a ray of hope. Artificial antisense oligonucleotides (ASOs) are now best known for their use in spinal muscular atrophy (SMA). The success of nusinersen/Spinraza for SMA indicates ASO-therapies' potential for other rare conditions. We propose a strategy to develop N-of-1 ASOs for treating one form of trichothiodystrophy (TTD), a rare condition with multisystem abnormalities and reduced life expectancy, associated with instability and greatly reduced amounts of the DNA-repair/transcription factor TFIIH. The therapeutic target carry mutations in GTF2H5, encoding the TFIIH-p8 subunit. This approach was inspired by the diagnosis and molecular dissection of a xeroderma pigmentosum (XP) case with mutations in GTF2H4, encoding the TFIIH-p52 subunit. This is newly classified as a ninth XP complementation-group, XP-J, identified five decades after the discovery of the other XP complementation-groups. The p8-p52 interaction is required to support the TFIIH-complex formation, and the patient's p52 C-terminal truncation results in the complete absence of p8 in TFIIH. However, intriguingly, TFIIH remained stable in vivo, and the XP-J patient did not exhibit any TTD-features. The aim of our ASO-design is to induce a C-terminal truncation of p52 and we have successfully stabilised TFIIH in p8-deficient TTD-A patient cells.
Authors
Yuka Nakazawa, Lin Ye, Yasuyoshi Oka, Hironobu Morinaga, Kana Kato, Mayuko Shimada, Kotaro Tsukada, Koyo Tsujikawa, Yosuke Nishio, Hiva Fassihi, Shehla Mohammed, Alan R. Lehmann, Tomoo Ogi
Abstract
Authors
Hiva Fassihi, Shehla Mohammed, Yuka Nakazawa, Heather Fawcett, Sally Turner, Joanne Palfrey, Isabel Garrood, Adesoji Abiona, Ana M.S. Morley, Mayuko Shimada, Kana Kato, Alan R. Lehmann, Tomoo Ogi
Abstract
Sweet syndrome (also known as acute febrile neutrophilic dermatosis) is a rare inflammatory skin disorder characterized by erythematous plaques with a dense dermal neutrophilic infiltrate. First-line therapy remains oral corticosteroids, which suppresses inflammation non-specifically. Although neutrophils are typically short-lived, how they persist in Sweet syndrome skin and contribute to disease pathogenesis remains unclear. Here, we identify a previously unrecognized population of antigen-presenting cell (APC)-like neutrophils expressing MHC class II genes that are uniquely present in Sweet syndrome skin but absent from healthy tissue and circulation. Keratinocytes extended neutrophil lifespan 10-fold in co-culture experiments and drove the emergence of an APC-like phenotype in approximately 30% of neutrophils, mirroring observations in patient lesions. Mechanistically, keratinocyte-derived serum amyloid A1 (SAA1) signals through the formyl peptide receptor 2 (FPR2) on neutrophils to promote their survival. These long-lived neutrophils actively orchestrate local immune responses by recruiting T cells and inducing cytokine production. Strikingly, dual blockade of SAA1-FPR2 signaling restores neutrophil turnover to baseline levels, with efficacy comparable to high-dose corticosteroids. These findings uncover a keratinocyte-neutrophil-T cell axis that sustains chronic inflammation in Sweet syndrome and highlight the SAA1/FPR2 pathway as a promising target for precision therapy.
Authors
Jianhe Huang, Satish Sati, Olivia Ahart, Emmanuel Rapp-Reyes, Linda Zhou, Robert G. Micheletti, William D. James, Misha Rosenbach, Thomas H. Leung
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)