Heterozygous mutations in the C-terminal domain of COPA underlie a complex autoinflammatory syndrome

Mutations in the N-terminal WD40 domain of coatomer protein complex subunit α (COPA) cause a type I interferonopathy, typically characterized by alveolar hemorrhage, arthritis, and nephritis. We described 3 heterozygous mutations in the C-terminal domain (CTD) of COPA (p.C1013S, p.R1058C, and p.R1142X) in 6 children from 3 unrelated families with a similar syndrome of autoinflammation and autoimmunity. We showed that these CTD COPA mutations disrupt the integrity and the function of coat protein complex I (COPI). In COPAR1142X and COPAR1058C fibroblasts, we demonstrated that COPI dysfunction causes both an anterograde ER-to-Golgi and a retrograde Golgi-to-ER trafficking defect. The disturbed intracellular trafficking resulted in a cGAS/STING-dependent upregulation of the type I IFN signaling in patients and patient-derived cell lines, albeit through a distinct molecular mechanism in comparison with mutations in the WD40 domain of COPA. We showed that CTD COPA mutations induce an activation of ER stress and NF-κB signaling in patient-derived primary cell lines. These results demonstrate the importance of the integrity of the CTD of COPA for COPI function and homeostatic intracellular trafficking, essential to ER homeostasis. CTD COPA mutations result in disease by increased ER stress, disturbed intracellular transport, and increased proinflammatory signaling.

COPA Syndrome from Diagnosis to Treatment: A Clinician's Guide

COPA syndrome is a recently described autosomal dominant inborn error of immunity characterized by high titer autoantibodies and interstitial lung disease, with many individuals also having arthritis and nephritis. Onset is usually in early childhood, with unique disease features including alveolar hemorrhage, which can be insidious, pulmonary cyst formation, and progressive pulmonary fibrosis in nonspecific interstitial pneumonia or lymphocytic interstitial pneumonia patterns. This review explores the clinical presentation, genetics, molecular mechanisms, organ manifestations, and treatment approaches for COPA syndrome, and presents a diagnostic framework of suggested indications for patient testing.

COPA silences STING

Two studies published in this issue of JEM, by Lepelley et al. (https://doi.org/10.1084/jem.20200600) and Deng et al. (https://doi.org/10.1084/jem.20201045), and two additional manuscripts by Mukai et al. (https://doi.org/10.1101/2020.05.20.107664 Preprint v1) and Steiner et al. (https://doi.org/10.1101/2020.07.09.194399 Preprint v1) demonstrate that COPA syndrome-associated high interferon titers are linked to mutations in COPA preventing STING's retrieval from the Golgi back to the ER and thereby causing chronic immune activation.

An unprecedented COPA gene mutation in two patients in the same family: comparative clinical analysis of newly reported patients with other known COPA gene mutations

INTRODUCTION

The COPA syndrome is a newly recognized monogenic, autosomal dominant autoimmune disease presenting mostly presenting in childhood. Clinical features include inflammation of the lungs, kidneys, and joints. Approximately twenty-six patients with COPA syndrome worldwide have been investigated all originating from eight families. Patients with this syndrome exhibit heterozygous monogenic missense mutations in the WD40 domain. This domain is a functionally-significant area of the alpha subunit of coatomer-associated protein (COPα) which encodes the coat protein complex I (COPI). The COPI dysfunction is also associated with autoantibody expansion. We report two patients with COPA syndrome.

METHODS

All testing and molecular genetic analysis were performed after obtaining the informed consent of both the patient and parents. A retrospective chart review was carried out on both the patients. Demographic, clinical and laboratory findings were abstracted from outpatient and inpatient encounters. Pulmonary function tests (PFTs), chest computed tomography (CT) scans, and lung biopsy histopathology reports were also reviewed and summarized.

RESULTS

The index case and the father of the child both demonstrated a unique inflammatory pulmonary, arthritis, and renal disease triad starting in early childhood including pulmonary hemorrhage. The two patients had a novel COPA mutation previously undescribed.

CONCLUSIONS

To date, only four pathological, genetic mutations have been reported that are compatible with COPA syndrome. We here report two patients with COPA syndrome within the same family with a novel COPA gene mutation different than the heterozygous monogenic missense mutations in the WD40 domain and distinct from the clinical phenotypes reported in the literature so far.

Expanding the phenotype of COPA syndrome: a kindred with typical and atypical features

Background

Copa syndrome is a rare autosomal dominant disorder with abnormal intracellular vesicle trafficking. The objective of this work is to expand the knowledge about this disorder by delineating phenotypic features of an unreported COPA family.

Methods and results

A heterozygous missense variant (c.698 G>A, p.Arg233His) in COPA was identified in four members of a three-generation kindred with lung, autoimmune and malignant disease of unknown aetiology. Ages of onset were 56, 26, 16 and 1 year, with earlier age of onset in successive generations. Presenting symptoms were cough and dyspnoea. Findings included small lung cysts, follicular bronchiolitis, interstitial lung disease, neuroendocrine cell hyperplasia, rheumatoid arthritis, avascular necrosis and select abnormal autoimmune serologies. Neither alveolar haemorrhage nor glomerular disease were present. Features not previously associated with Copa syndrome included neuromyelitis optica, pulmonary carcinoid tumour, clear cell renal carcinoma, renal cysts, hepatic cysts, nephrolithiasis, pyelonephritis and meningitis. Longitudinal evaluations demonstrated slow progression of lung disease and extrapulmonary cysts.

Conclusions

Worsening severity with successive generations may be observed in Copa syndrome. Extrapulmonary cysts, malignancies, autoimmune neurological disorders and infections are clinical features that may be associated with Copa syndrome. Further studies are indicated to fully define the phenotypic spectrum of this disorder.