2026-07-04 | The SNRPN Bipartite Imprinting Centre in Region 15q11–q13 and Its Epigenetic Role in the Pursuit of a Cure for Angelman Syndrome

Angelman syndrome is a severe neurodevelopmental disorder arising from functional loss of the maternal allele of UBE3A, a gene that sits within a cluster of imprinted loci on the long arm of chromosome 15. Expression across this region is governed by a bipartite imprinting centre associated with the SNRPN gene, made up of two physically separated but functionally interdependent elements: the Prader–Willi syndrome smallest region of deletion overlap and the Angelman syndrome smallest region of deletion overlap. Together these elements establish, in the germline, and maintain, throughout somatic life, the parent-of-origin-specific expression pattern that distinguishes Angelman syndrome from its reciprocal disorder, Prader–Willi syndrome. Because the paternal copy of UBE3A remains structurally intact in most patients with Angelman syndrome, merely silenced by a long non-coding antisense transcript whose own expression is dictated by the imprinting centre, this locus has become the focal point of an unusually concentrated translational effort: rather than replacing a missing gene, contemporary therapeutic strategies aim to reverse an epigenetic mark and thereby unmask a dormant but functional allele. This review draws together the structural biology of the bipartite imprinting centre, the molecular events that establish and maintain its parent-specific epigenotype, the diagnostic and clinical consequences of its disruption, and the rapidly maturing pipeline of antisense oligonucleotides, small molecules, and genome- or epigenome-editing tools designed to exploit this biology therapeutically. Recent clinical trial data, including electroencephalographic and behavioural endpoints from antisense oligonucleotide programmes, are critically appraised alongside preclinical work on CRISPR-based epigenetic editing of the imprinting centre itself, an approach with the conceptual elegance of intervening at the very switch that imprinting biology depends upon. The review concludes that while no disease-modifying therapy is yet approved, the convergence of detailed mechanistic understanding of the SNRPN bipartite imprinting centre with scalable epigenetic editing technologies represents the most plausible route towards a transformative, rather than purely symptomatic, treatment for Angelman syndrome, while candidly addressing the developmental, safety and translational obstacles that remain.

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2026-07-01 | Pseudohypoaldosteronism associated with mitochondrial dysfunction in Angelman syndrome

Pseudohypoaldosteronism (PHA) is an uncommon cause of hyperkalemic metabolic acidosis in infancy, typically secondary to structural, infectious, or genetic etiologies. Because renal tubular transport is adenosine triphosphate dependent, mitochondrial dysfunction may also produce a PHA-like phenotype. We report a 14-month-old girl with hyperkalemic metabolic acidosis and growth failure. Laboratory evaluation showed hyperkalemic metabolic acidosis with markedly elevated renin and aldosterone, consistent with a PHA-like phenotype. Bicarbonate and potassium-binding treatment provided suboptimal control. Organic acid abnormalities and an elevated lactate-to-pyruvate ratio raised suspicion of mitochondrial dysfunction, and vitamin supplementation (vitamin B, vitamin C, biotin, L-carnitine, and idebenone) promptly normalized acid-base status and potassium. Continued oral vitamin supplementation was associated with catch-up growth and allowed gradual tapering and eventual discontinuation of bicarbonate and potassium-binding agent at 1.8 and 3.4 years, respectively. The oxygen consumption rate in the fibroblasts was markedly reduced in galactose medium. For genetic analyses, targeted PHA/renal tubular acidosis-related gene panel testing, mitochondrial DNA sequencing and exome sequencing identified no pathogenic variants, whereas chromosomal microarray analysis identified a 5.76 Mb deletion in 15q (arr[hg19] 15q11.2q13.1(22,765,628-28,525,460) × 1), establishing the diagnosis of Angelman syndrome. This case links a PHA-like presentation, growth failure, and mitochondrial dysfunction to Angelman syndrome, supporting bioenergetic failure as a potentially treatable mechanism for refractory PHA.

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2026-06-30 | Waking the Silent Gene in Angelman Syndrome

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.

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