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BACKGROUND: PTEN hamartoma tumour syndrome (PHTS) encompasses distinct syndromes, including Cowden syndrome resulting from PTEN pathogenic variants. Missense variants account for 30% of PHTS cases, but their classification remains challenging. To address these difficulties, guidelines were published by the Clinical Genome Resource PTEN Variant Curation Expert Panel. METHODS: Between 2010 and 2020, the Bergonie Institute reference laboratory identified 76 different non-truncating PTEN variants in 166 patients, 17 of which have not previously been reported. Variants were initially classified following the current guidelines. Subsequently, a new classification method was developed based on four main criteria: functional exploration, phenotypic features and familial segregation, in silico modelling, and allelic frequency. RESULTS: This new method of classification is more discriminative and reclassifies 25 variants, including 8 variants of unknown significance. CONCLUSION: This report proposes a revision of the current PTEN variant classification criteria which at present rely on functional tests evaluating only the phosphatase activity of PTEN and apply a particularly stringent clinical PHTS score.The classification of non-truncating variants of PTEN is facilitated by taking into consideration protein stability for variants with intact phosphatase activity, clinical and segregation criteria adapted to the phenotypic variability of PHTS and by specifying the allelic frequency of variants in the general population. This novel method of classification remains to be validated in a prospective cohort.
RESUMEN
BACKGROUND: The development of whole-exome sequencing (WES) and whole-genome sequencing (WGS) for clinical purposes now allows the identification of multiple pathogenic variants in patients with a rare disease. This occurs even when a single causative gene was initially suspected. We report the case of an 8-year-old patient with global developmental delays and dysmorphic features, with a possibly pathogenic variant in three distinct genes. METHODS: Trio-based exome sequencing was performed by IntegraGen SA (Evry, France), on an Illumina HiSeq4000 (Illumina, San Diego, CA, USA). Sanger sequencing was performed to confirm the variants that were found. RESULTS: WES showed the presence of three possibly deleterious variants: KMT2A: c.9068delA;p.Gln3023Argfs*3 de novo, PAX3: c.530C>G;p.Ala177Gly de novo and DLG3: c.127delG;p.Asp43Metfs*22 hemizygous inherited from the mother. KMT2A pathogenic variants are involved in Wiedemann-Steiner syndrome, and PAX3 is the gene responsible for Waardenburg syndrome. DLG3 variants have been described in a non-syndromic X-related intellectual disability. CONCLUSIONS: Considering the dysmorphic features and intellectual disability presented by this patient, these three variants were imputed as pathogenic and their association was considered responsible for his phenotype. Dual molecular diagnoses have already been found by WES in several cohorts with an average of diagnostic yield of 7%. This case demonstrates and reminds us of the importance of analyzing exomes rigorously and exhaustively because, in some cases (< 10%), it can explain superimposed traits or blended phenotypes.
Asunto(s)
Anomalías Múltiples/diagnóstico , Anomalías Múltiples/genética , Discapacidad Intelectual/diagnóstico , Discapacidad Intelectual/genética , Síndrome de Waardenburg/diagnóstico , Síndrome de Waardenburg/genética , Síndrome de Beckwith-Wiedemann , Niño , Predisposición Genética a la Enfermedad , N-Metiltransferasa de Histona-Lisina/genética , Humanos , Masculino , Técnicas de Diagnóstico Molecular , Mutación , Proteína de la Leucemia Mieloide-Linfoide/genética , Proteínas Nucleares/genética , Factor de Transcripción PAX3/genética , Factores de Transcripción/genética , Secuenciación del ExomaRESUMEN
It was hypothesized that variants in underexplored homologous recombination repair (HR) genes could explain unsolved multiple-case breast cancer (BC) families. We investigated HR deficiency (HRD)-associated mutational signatures and second hits in tumor DNA from familial BC cases. No candidates genes were associated with HRD in 38 probands previously tested negative with gene panels. We conclude it is unlikely that unknown HRD-associated genes explain a large fraction of unsolved familial BC.