A case of a Tunisian Rett patient with a novel double-mutation of the MECP2 gene

► Sequencing of the MECP2 gene, modeling and comparison of the two variants were performed in a Tunisian classical Rett patient. ► A double-mutation: a new and de novo mutation c.535C > T and the common one c.763C > T of the MECP2 gene was identified. ► The P179S transition may change local electrostatic properties which may affect the function and stability of the protein MeCP2. Rett syndrome is an X-linked dominant disorder caused frequently by mutations in the methyl-CpG-binding protein 2 gene ( MECP2). Rett patients present an apparently normal psychomotor development during the first 6–18 months of life. Thereafter, they show a short period of developmental stagnation followed by a rapid regression in language and motor development. The aim of this study was to perform a mutational analysis of the MECP2 gene in a classical Rett patient by sequencing the corresponding gene and modeling the found variants. The results showed the presence of a double-mutation: a new and de novo mutation c.535C > T (p.P179S) and the common c.763C > T (p.R255X) transition of the MECP2 gene. The p.P179S mutation was located in a conserved amino acid in CRIR domain (corepressor interacting region). Modeling results showed that the P179S transition could change local electrostatic properties by adding a negative charge due to serine hydroxyl group of this region of MeCP2 which may affect the function and stability of the protein. The p.R255X mutation is located in TRD-NLS domain (transcription repression domain-nuclear localization signal) of MeCP2 protein.