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RESEARCH PRODUCT

Genomic characterization of mosaic cutaneous pigmentary disorders

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description

Ntroduction: Mosaic cutaneous dyschromia is strongly evocative of an underlying genetic mosaicism. These post-zygotic events are challenging for conventional diagnostic tools. Thus, genetic basis of mosaic cutaneous dyschromia still remained poorly understood. Materials and Methods: The M.U.S.T.A.R.D. cohort gathers DNA from skin biopsies of patients with mosaic cutaneous dyschromia. After a specialised phenotype analysis, they are referred to either trio exome sequencing (ES) at 200X, or targeted ultra-deep sequencing (60,000X) of candidate genes. Data are analysed with a tailored pipeline, allowing detection of both low-rate nucleotidic variations or chromosomal events. Results: From 2013 to 2019, 101 patients were included. ES was performed for 56, with identification of mosaic SNV in 12 patients in 7 new genes, including 4 new genes (RHOA, DOCK1, GNA13, TFE3), and mosaic chromosomal anomalies in 17 patients. A targeted sequencing of these genes was performed for 40 more patients, with a confirmed mosaic SNV in 17, and a global diagnostic yield of 55% (46/84). Conclusion: This work highlights the importance of a versatile bioinformatic approach combined to a clinical expertise, to decipher the chromosomal and molecular aetiologies of developmental anomalies with mosaic cutaneous dyschromia. It also pinpoints the role of the Rho GTPase pathway, which will help enhancing our understanding of mosaic cutaneous dyschromia, and may ultimately result in better patients’ care.