4.7 Article

First Genotype-Phenotype Study in TBX4 Syndrome Gain-of-Function Mutations Causative for Lung Disease

Journal

Publisher

AMER THORACIC SOC
DOI: 10.1164/rccm.202203-0485OC

Keywords

pulmonary arterial hypertension; TBX4; interstitial lung disease; lung developmental disease; gain-of-function

Funding

  1. NIHR Great Ormond Street Hospital Biomedical Research Centre
  2. Great Ormond Street Hospital Charity
  3. Medical Research Council [MR/K020919/1]
  4. Dinosaur Trust
  5. Fundacion Contra la Hipertension Pulmonar
  6. NIHR Cambridge Biomedical Research Centre
  7. Dutch Heart Foundation [CVON2017-4 DOLPHIN-GENESIS]
  8. British Heart Foundation [FS/18/13/3328]
  9. Instituto de Salud Carlos III [PI18/01233]
  10. Conselleria de Cultura, Educacion e Ordenacion Universitaria, Xunta de Galicia [ED431G/02]
  11. Xunta de Galicia predoctoral fellowship [ED481A-2018/304]
  12. Wellcome Trust fellowship [205188/Z/16/Z]

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This study analyzed TBX4-associated pulmonary arterial hypertension and found that TBX4 variants can cause both loss-of-function and gain-of-function effects. The differential impact of pathogenic mutations located in critical protein domains may explain the pleiotropic effects of TBX4 in lung disease.
Rationale: Despite the increased recognition of TBX4 (T-BOX transcription factor 4)-associated pulmonary arterial hypertension (PAH), genotype-phenotype associations are lacking and may provide important insights. Objectives: To compile and functionally characterize all TBX4 variants reported to date and undertake a comprehensive genotype-phenotype analysis. Methods: We assembled a multicenter cohort of 137 patients harboring monoallelic TBX4 variants and assessed the pathogenicity of missense variation (n = 42) using a novel luciferase reporter assay containing T-BOX binding motifs. We sought genotype-phenotype correlations and undertook a comparative analysis with patients with PAH with BMPR2 (Bone Morphogenetic Protein Receptor type 2) causal variants (n = 162) or no identified variants in PAH-associated genes (n = 741) genotyped via the National Institute for Health Research BioResource-Rare Diseases. Measurements and Main Results: Functional assessment of TBX4 missense variants led to the novel finding of gain-of-function effects associated with older age at diagnosis of lung disease compared with loss-of-function effects (P = 0.038). Variants located in the T-BOX and nuclear localization domains were associated with earlier presentation (P = 0.005) and increased incidence of interstitial lung disease (P = 0.003). Event-free survival (death or transplantation) was shorter in the T-BOX group (P = 0.022), although age had a significant effect in the hazard model (P = 0.0461). Carriers of TBX4 variants were diagnosed at a younger age (P, 0.001) and had worse baseline lung function (FEV1, FVC) (P = 0.009) than the BMPR2 and no identified causal variant groups. Conclusions: We demonstrated that TBX4 syndrome is not strictly the result of haploinsufficiency but can also be caused by gain of function. The pleiotropic effects of TBX4 in lung disease may be in part explained by the differential effect of pathogenic mutations located in critical protein domains.

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