Mutation in the SLC9A6 gene is not a frequent cause of sporadic Angelman-like syndrome

Angelman syndrome (AS) (MIM #105530) is a neurodevelopmental disorder characterized by a broad range of clinical features, such as profound mental retardation, impairment of verbal language, usually ataxia, subtle dysmorphic facial features, a peculiar behavioral profile, with a happy disposition and outbursts of laughter, and a seizure disorder associated with a characteristic electroencephalographic pattern.1 It affects between 1:15 000 and 1:40 000 newborn children depending on ethnical and geographical areas.2, 3, 4, 5 Most cases of AS are sporadic, although several familial cases have been reported. A variety of different genetic mechanisms involving chromosome 15q11.2-13 (deletion, paternal uniparental disomy, imprinting center abnormality, and UBE3A (MIM #601623; 15q11.2) mutations) have been described in association with AS, all resulting in a deficiency of the ubiquitin-protein ligase E3A, which is involved in the process of ubiquitination.6 In some cases, patients with AS share common features with patients affected by Rett syndrome (MIM #312750).7 After extensive cytogenetic and molecular analysis of chromosome 15q11-13, there remains a small group of about 10–15% of AS patients, in whom no abnormality can be identified.