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Mutation analysis of MECP2 and determination of the X‐inactivation pattern in Hungarian Rett syndrome patients

Mutations in the gene encoding methyl-CpG-binding protein 2 (MeCP2) have been associated with the causation of Rett syndrome [Buyse et al., 2000], an X-linked dominant neurodevelopmental disorder with characteristic, although variable phenotype. Since no consistent correlation is known yet between the type of mutation and the clinical manifestation or outcome, other modulating effects have been investigated to understand genotype–phenotype correlation [Amir et al., 2000]. Recently, Weaving et al. [2003] reported in this Journal a higher rate of skewed X-inactivation than would be expected. They also suggested that the type or domain location of the mutation, and X-inactivation might influence the phenotype through complex interactions. This finding prompted us to report on our similar observation. We performed mutation analysis of MECP2 in 27 Hungarian Rett syndrome patients and found mutation in 19 cases (70%). This percentage is similar to that reported by other authors [Nielsen et al., 2001]. Nine previously described mutations were detected in 16 patients (R294X in three patients, R106W, R133C, R168X, T158M, and R270X in two patients each, P152R, R255X, and 1157del41 once each) and three novel mutations in three patients (276insG; 1160del7; 1121del191, 1332del9) (a detailed report is in preparation). Of the 19, 15 patients have the classical and four the atypical form of the disease. X-inactivation analysis was performed in 15 patients with mutation (in four cases, we could not obtain blood samples from both parents). In three patients X-inactivation pattern was not informative, in five patients random, and in seven patients non-random X-inactivation was found. The incidence of skewed X-inactivation (7/15) is similar to that in Weaving et al. [2003] study (43%). Although the number of patients in our study is much less than theirs, this result supports the suggestion of Weaving et al. that in Rett syndrome patients with confirmed mutation skewed X-inactivation is a significant modulating factor in about half of the cases.