A COMPARATIVE-STUDY OF X-INACTIVATION IN RETT-SYNDROME PROBANDS AND CONTROL SUBJECTS

X-inactivation has been studied in a series of monozygotic female twin s and their female relatives by a PCR method which detects methylation at the androgen receptor locus (HUMARA). The results obtained are com pared to those from an earlier study employing probe M27 beta which de tects locus DXS255. Analysis of X-inactivation in girls with Rett synd rome and their mothers by four different methods did not indicate a di rect relationship between non-random inactivation of the X-chromosome and the presence of the disease with the exception that any skewing de tected in the probands tended to favour the preferential inactivation of the paternally inherited X-chromosome. No evidence for the involvem ent of uniparental disomy in the etiology of the disease was found.