Variant STAT4 and Response to Ruxolitinib in an Autoinflammatory Syndrome

Hratch Baghdassarian1, Sarah A Blackstone1, Owen S Clay1

  • 1From the Bioinformatics and Systems Biology Program (H.B.), the Department of Pediatrics (H.B., O.S.C., V.K.H., N.E.L.), the Center for Computational Biology and Bioinformatics, Department of Medicine (A.M., R.S., K.M.F.), the Institute for Genomic Medicine (K.J.), the Department of Bioengineering (N.E.L.), the Division of Allergy, Immunology, and Rheumatology, Department of Pediatrics (J.C., L.B.), and the Department of Medicine (C.D.P.), University of California, San Diego, Sanford Burnham Prebys Medical Discovery Institute (R.M., Y.L.), and the San Diego Branch, Ludwig Institute for Cancer Research (C.D.P.), La Jolla, and the Department of Pathology (S.M.T.), Rady Children's Institute for Genomic Medicine (S.C., D.D.), and Rady Children's Hospital Foundation (J.C., L.B.), Rady Children's Hospital, San Diego - all in California; the Inflammatory Disease Section (S.A.B., B.M., M.N., S.R., P.P.C., N.H., E.F.R., D.L.K., H.O.), the Oncogenesis and Development Section (N.D.), and the Undiagnosed Diseases Program, Medical Genetics Branch (D.R.M., W.A.G.), National Human Genome Research Institute, the Molecular Immunology and Inflammation Branch (R.P., J.J.O.), the Light Imaging Section (D.R.) and the Translational Immunology Section (M.G.), Office of Science and Technology, and the Protein Expression Laboratory (E.E., N.R.W.), National Institute of Arthritis and Musculoskeletal and Skin Diseases, and the Genetics and Pathogenesis of Allergy Section, Laboratory of Allergic Diseases (C.A.M.), and the Translational Autoinflammatory Disease Section (R.G.-M.), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, and the Department of Cell Biology and Molecular Genetics, University of Maryland, College Park (B.M.) - all in Maryland; Sanford School of Medicine, University of South Dakota, Sioux Falls (S.A.B.); the Division of Rheumatology and Clinical Immunology, University of Pittsburgh (D.M.S.), University of Pittsburgh Medical Center, Children's Hospital of Pittsburgh (A.S., G.W., K.T.), and the University of Pittsburgh Scleroderma Center (A.S., G.W., K.T.) - all in Pittsburgh; the Division of Pediatric Allergy, Immunology, and Rheumatology, Columbia University, New York (J.D.M.); and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases and the Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany (H.O.).

Abstract

Insights

Disabling pansclerotic morphea (DPM) is linked to novel STAT4 gene variants. Janus kinase (JAK) inhibitor ruxolitinib shows promise in treating this rare inflammatory disorder by improving skin and inflammatory symptoms.

Area of Science:

  • Genetics
  • Immunology
  • Dermatology

Background:

  • Disabling pansclerotic morphea (DPM) is a rare, severe systemic inflammatory disorder with high mortality.
  • Characterized by poor wound healing, fibrosis, cytopenias, hypogammaglobulinemia, and squamous-cell carcinoma.
  • The underlying cause of DPM remains unknown.

Purpose of the Study:

  • Investigate the genetic basis of DPM in families with an autosomal dominant inheritance pattern.
  • Define the functional consequences of identified genetic variants.
  • Identify potential therapeutic targets for DPM.

Main Methods:

  • Genomic sequencing of patients from three unrelated families.
  • In vitro assays using primary skin fibroblasts and cell lines.
  • Single-cell RNA sequencing of peripheral-blood mononuclear cells.
  • Inhibition of Janus kinase (JAK)-STAT signaling pathway.

Main Results:

  • Identified three novel heterozygous gain-of-function variants in the signal transducer and activator of transcription 4 (STAT4) gene.
  • In vitro studies showed enhanced interleukin-6 secretion and impaired wound healing in fibroblasts.
  • Ruxolitinib treatment improved the hyperinflammatory fibroblast phenotype in vitro and resolved clinical symptoms in patients.
  • Single-cell RNA sequencing confirmed an immunodysregulatory phenotype modified by JAK inhibition.

Conclusions:

  • Gain-of-function STAT4 variants are causative for DPM in the studied families.
  • Ruxolitinib effectively targets the JAK-STAT pathway, attenuating the dermatologic and inflammatory phenotype of DPM.
  • This study provides a potential therapeutic strategy for DPM.

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