Waking the Silent Gene in Angelman Syndrome

Abstract

Angelman syndrome is a severe neurogenetic disorder characterised by developmental delay, motor impairment, absent or markedly limited speech, epilepsy and a characteristic happy demeanour with frequent laughter. It results from loss of function of the maternally inherited UBE3A gene located in the 15q11-q13 chromosomal region, while the paternal allele is normally epigenetically silenced in neurons by the long non-coding antisense transcript UBE3A-ATS. The estimated prevalence is approximately 1 in 15,000 to 1 in 20,000 individuals. Maternal chromosome 15 deletion accounts for approximately 70-75% of cases, whereas paternal uniparental disomy, imprinting defects and UBE3A sequence variants represent additional mechanisms. Diagnosis is generally established between 1 and 4 years of age through DNA methylation analysis and complementary molecular testing, when developmental delay, impaired balance and other clinical features become apparent. Current treatment remains supportive and multidisciplinary, including physiotherapy, occupational therapy, speech and augmentative communication support, seizure management, sleep regulation and assistive devices. This minireview summarises the genetic background of Angelman syndrome, present symptomatic therapy and emerging approaches designed to restore neuronal UBE3A activity. Particular attention is given to antisense oligonucleotides, including ION582, GTX-102 and rugonersen, as well as AAV-mediated gene replacement and CRISPR-Cas9-based gene-reactivation strategies. These approaches seek either to unsilence the paternal UBE3A allele or to deliver functional UBE3A to the nervous system. Although early clinical and preclinical findings are encouraging, none of the investigational strategies discussed here can yet be considered curative. Long-term evidence regarding efficacy, dosing, delivery, tolerability and safety remains essential before routine use in children with Angelman syndrome can be justified.