{
  "abstract": "Background Hereditary haemorrhagic telangiectasia (HHT) and juvenile polyposis syndrome (JPS) can be caused by SMAD4 pathogenic variants. SMAD4 is a common transcription factor of the BMP/TGFβ signalling pathway. In this study, we developed a cell-based functional assay to address the pathogenicity of SMAD4 variants identified in the French HHT cohort.Methods SMAD4 variants were generated by site-directed mutagenesis. A functional assay was developed in a cell line that does not express SMAD4, and the different SMAD4 variants were tested for their capacity to activate the BMP and TGFβ response using luciferase reporter assays.Results Twelve SMAD4 variants were identified and studied. We were able to develop a robust functional assay for these variants. All the expressed variants resulted in loss of function (LOF) in response to BMP9 or TGFβ1 stimulation. SMAD4 variants within the MH2 domain expressed SMAD4 mutated proteins that were unable to hetero-oligomerise with other SMADs, which could explain their LOF. Finally, we tested primary human endothelial cells isolated from patients with HHT carrying SMAD4 heterozygous pathogenic variants and observed that they behaved like the control cells at rest or when stimulated with BMP9.Conclusion We developed a SMAD4 functional assay that allows discrimination between benign and pathogenic SMAD4 variants. We demonstrated that the underlying molecular mechanism of this pathogenicity is due mostly to a loss of hetero-oligomerisation. This assay will be transferable to clinical genetic laboratories and will improve the diagnosis of patients with HHT–JPS.",
  "authors": [
    {
      "affiliations": [
        "Biosanté unit U1292, Grenoble Alpes University, INSERM, CEA, INSERM, Grenoble, France"
      ],
      "name": "Louane Despas"
    },
    {
      "affiliations": [
        "Biosanté unit U1292, Grenoble Alpes University, INSERM, CEA, INSERM, Grenoble, France"
      ],
      "name": "Lea Vialet"
    },
    {
      "affiliations": [
        "Hospices Civils de Lyon, National HHT Reference Center and Genetics Department, Hospices Civils de Lyon, Bron, France"
      ],
      "name": "Maud Tusseau"
    },
    {
      "affiliations": [
        "Biosanté unit U1292, Grenoble Alpes University, INSERM, CEA, INSERM, Grenoble, France"
      ],
      "name": "Valentin Azemard"
    },
    {
      "affiliations": [
        "Biosanté unit U1292, Grenoble Alpes University, INSERM, CEA, INSERM, Grenoble, France"
      ],
      "name": "Lea Beurier-Soulat"
    },
    {
      "affiliations": [
        "Biosanté unit U1292, Grenoble Alpes University, INSERM, CEA, INSERM, Grenoble, France"
      ],
      "name": "Tala Al Tabosh"
    },
    {
      "affiliations": [
        "Hospices Civils de Lyon, National HHT Reference Center and Genetics Department, Hospices Civils de Lyon, Bron, France"
      ],
      "name": "Celine Auboiroux"
    },
    {
      "affiliations": [
        "Paris Competence Center for HHT, Hôpital Tenon, Paris, France"
      ],
      "name": "Antoine Parrot"
    },
    {
      "affiliations": [
        "Boulogne-Billancourt Competence Center for HHT, AP-HP, Boulogne-Billancourt, France"
      ],
      "name": "Sandra Blivet"
    },
    {
      "affiliations": [
        "Poitiers Competence Center for HHT, Centre Hospitalier Universitaire de Poitiers, Poitiers, France"
      ],
      "name": "Xavier Maximin Le Guillou Horn"
    },
    {
      "affiliations": [
        "Hospices Civils de Lyon, National HHT Reference Center and Genetics Department, Hospices Civils de Lyon, Bron, France"
      ],
      "name": "Gaetan Lesca"
    },
    {
      "affiliations": [
        "CHU de Poitiers, Service de Génétique, Centre Hospitalier Universitaire de Poitiers, Poitiers, France"
      ],
      "name": "Fabienne Dufernez"
    },
    {
      "affiliations": [
        "Inserm, Team ‘Microsatellite Instability and Cancer’, UMRS 938, AP-HP, Paris, France"
      ],
      "name": "Florence Coulet"
    },
    {
      "affiliations": [
        "Hospices Civils de Lyon, National HHT Reference Center and Genetics Department, Hospices Civils de Lyon, Bron, France"
      ],
      "name": "Charlotte Richardot"
    },
    {
      "affiliations": [
        "Institute for Research in Biomedicine (IRB Barcelona), Baldiri Reixac 10, Institute for Research in Biomedicine, Barcelona, Spain",
        "ICREA, Passeig Lluís Companys 23, 08010-Barcelona, Spain, Genetics Department, ICREA, Barcelona, Spain"
      ],
      "name": "Maria Macias"
    },
    {
      "affiliations": [
        "Hospices Civils de Lyon, National HHT Reference Center and Genetics Department, Hospices Civils de Lyon, Bron, France",
        "Institut Bergonié, Centre Hospitalier de la Cote Basque, Bayonne, France"
      ],
      "name": "Sophie Giraud"
    },
    {
      "affiliations": [
        "Hospices Civils de Lyon, National HHT Reference Center and Genetics Department, Hospices Civils de Lyon, Bron, France"
      ],
      "name": "Alexandre Guilhem"
    },
    {
      "affiliations": [
        "Biosanté unit U1292, Grenoble Alpes University, INSERM, CEA, INSERM, Grenoble, France",
        "Hospices Civils de Lyon, National HHT Reference Center and Genetics Department, Hospices Civils de Lyon, Bron, France"
      ],
      "name": "Sophie Dupuis-Girod"
    },
    {
      "affiliations": [
        "Biosanté unit U1292, Grenoble Alpes University, INSERM, CEA, INSERM, Grenoble, France"
      ],
      "name": "Sabine Bailly"
    },
    {
      "affiliations": [
        "Biosanté unit U1292, Grenoble Alpes University, INSERM, CEA, INSERM, Grenoble, France"
      ],
      "name": "Agnes Desroches-Castan"
    }
  ],
  "title": "Development of a functional assay for the characterisation of SMAD4 variants from the French haemorrhagic hereditary telangiectasia cohort",
  "uid": "49b681ef-fca4-5bd7-a48e-72c1def07a57"
}