Objective-Angelman syndrome (AS) is a neurodevelopmental disorder caused by a deletion on chromosome 15, uniparental disomy (UPD), imprinting defect, or UBE3A mutation. It is characterized by intellectual disability with minimal speech and certain behavioral characteristics. We used standardized measures to characterize the developmental profile and to analyze genotype-phenotype correlations in AS.Method-The study population consisted of 92 children, between 5 months and 5 years of age, enrolled in a Natural History Study. Each participant was evaluated using the Bayley Scales of Infant and Toddler Development (Third Edition) (BSID-III), the Vineland Adaptive Behavior Scales (Second Edition) (VABS-II), and the Aberrant Behavior Checklist.Results-74% had a deletion and 26% had UPD, an imprinting defect or a UBE3A mutation ("non-deletion"). The mean±standard deviation (SD) BSID-III cognitive scale developmental quotient (DQ) was 40.5±15.5. Participants with deletions were more developmentally delayed than the non-deletion participants in all BSID-III domains except in expressive language skills. The ‡ Corresponding author and current affiliation: Sarika U. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript cognitive DQ was higher than the DQ in each of the other domains, and the receptive language DQ was higher than the expressive language DQ. In the VABS-II, deletion participants had weaker motor and language skills than the non-deletion participants.Conclusion-Children with AS have a distinct developmental and behavioral profile; their cognitive skills are stronger than their language and motor skills, and their receptive language skills are stronger than expressive language skills. Developmental outcomes are associated with genotype, with deletion patients having worse outcomes than non-deletion patients.

Angelman syndrome (AS) is a neurodevelopmental disorder caused by a lack of expression of the maternal copy of UBE3A. Although the “classic” features of AS are well described, few large-scale studies have delineated the clinical features in AS. We present baseline data from 92 children with a molecular diagnosis of AS between 5 and 60 months old who are enrolled in the National Institutes of Health Rare Diseases Clinical Research Network Angelman Syndrome Natural History Study from January 2006 to March 2008. Seventy-four percent of participants had deletions, 14% had either uniparental disomy (UPD) or imprinting defects, and 12% had UBE3A mutations. Participants with UPD/imprinting defects were heavier (P = 0.0002), while those with deletions were lighter, than the general population (P < 0.0001). Twenty out of 92 participants were underweight, all of whom had deletions or UBE3A mutations. Eight out of 92 participants (6/13 (46%) with UPD/imprinting defects and 2/11 (18%) with UBE3A mutations) were obese. Seventy-four out of 92 participants (80%) had absolute or relative microcephaly. No participant was macrocephalic. The most common behavioral findings were mouthing behavior (95%), short attention span (92%), ataxic or broad-based gait (88%), history of sleep difficulties (80%), and fascination with water (75%). Frequent, easily provoked laughter was observed in 60%. Clinical seizures were reported in 65% of participants but all electroencephalograms (EEGs) were abnormal. We conclude that the most characteristic feature of AS is the neurobehavioral phenotype, but specific EEG findings are highly sensitive for AS. Obesity is common among those with UPD/imprinting defects.

Despite a lack of differences in cognition or adaptive behavior, individuals with Class I deletions have greater severity in ASD features and sensory aversions that remain over time. There are four genes (NIPA 1, NIPA 2, CYFIP1, and GCP5) missing in Class I and present in Class Il deletions, one or more of which may have a role in modifying the severity of social affect impairment, and level of restricted/repetitive behaviors in AS. Our results also suggest the utility of a dimensional, longitudinal approach to the assessment of ASD features in populations of individuals who are low functioning.

Angelman syndrome (AS) is caused by reduced or absent expression of the maternally inherited ubiquitin protein ligase 3A gene (UBE3A), which maps to chromosome 15q11–q13. UBE3A is subject to genomic imprinting in neurons in most regions of the brain. Expression of UBE3A from the maternal chromosome is essential to prevent AS, because the paternally inherited gene is not expressed, probably mediated by antisense UBE3A RNA. We hypothesized that increasing methylation might reduce expression of the antisense UBE3A RNA, thereby increasing UBE3A expression from the paternal gene and ameliorating the clinical phenotype. We conducted a trial using two dietary supplements, betaine and folic acid to promote global levels of methylation and attempt to activate the paternally inherited UBE3A gene. We performed a number of investigations at regular intervals including general clinical and developmental evaluations, biochemical determinations on blood and urine, and electroencephalographic studies. We report herein the data on 48 children with AS who were enrolled in a double-blind placebo-controlled protocol using betaine and folic acid for 1 year. There were no statistically significant changes between treated and untreated children; however, in a small subset of patients we observed some positive trends.