Professionals

Angelman Syndrome an overview

75% Deletion

The majority of AS cases are caused by deletions on the maternal copy of Chromosome 15. This deletion prevents the normal expression of a gene called UBE3A in individuals with AS.

10%  UBE3A mutation

Mutations in the UBE3A gene either prevent its expression or function. Thus these individuals do not have the appropriate levels of functional UBE3A in the brain.

7 % Uniparental Disomy

In UPD, the individual has two copies of paternal Chromosome 15. Because UBE3A is not expressed from the paternal copy, these individuals lack normal levels of UBE3A in the brain.

5% Clinical/Other

In these individuals, all testing for Angelman Syndrome is normal, but they still meet the diagnostic criteria for AS. Please note that there are several other syndromes that present like AS that can be tested for

3%  Imprinting defect These individuals may have a deletion of the imprinting centre an Chromosome 15. Loss of imprinting will prevent expression of the maternal UBE3A gene in the brain.

NOTE: The National  Centre for Medical Genetics  Ireland also provides a comprehensive explanation of the current testing methods for this  chromosome disorder

http://www.genetics.ie/molecular/angelman-syndrome/

Timeline of Angelman Syndrome

1965 –   Dr Harry Angelman publishes a report entitled “Puppet Children” about 3 children he observed.

1980’s – Research into AS begins in University of Florida under the direction of Dr Charles Williams

1982 Name changed from ‘Happy Puppet’ to Angelman Syndrome

1987 Discovery that absent genetic code on maternal Chromosome 15 is the genetic marker for AS

1997 The cause of AS discovered by Dr. Joseph Wagstaff & Dr. Arthur Beaudet  mutation or deletion of UBE3A gene

2007   Neurological deficits can be reversed in a mouse model with AS

2011 Dr Ben Philpot discovers how to “switch on” the silent paternal genetic code on

Chromosome 15 in a mouse

2012  Dr Ed Weeber begins clinical trials with 24 children using Minocycline to treat cognition and motor function

The Future Hope Is in our Genes.

Summary report from the 6th International Scientific Conference, Hamburg, Germany by Annette Kent Bsc PhD, on behalf of Angelman Syndrome Ireland

Molecular mechanisms underlying Angelman Syndrome (AS) and investigating treatment options
Rosella Avagliano Trezza, Centre for Neurodevelopmental Disorders, Dept of Neurosciences, Erasmus MC, Netherlands
This work aimed to understand the key proteins in the cytoplasm and nucleus of the cell, exploring the circumstances under which the various forms of Ube3a move or are retained in either location. This work showed that 80% of the ube3a is the short form and 20% is the long form.
Removing the AZUL domain changed the location of the short form from nucleus to the cytoplasm and it is thought that the AZUL domain is necessary but not sufficient for Ube3a nuclear localization.
Doing experiments using leptomycin (inhibitor of movement from the nucleus) showed that the short form starts and stays nuclear however the short form without the Azul domain stays in the cytoplasm.
*AZUL domain is a specific location on Uba3e gene.
*Individual cells are comprised of a nucleus (the part of the cell that contains the genetic material) and the cytoplasm. The cytoplasm describes all the material in the cells outside of the nucleus.

A behavioural test battery for mouse models for AS: a powerful tool for testing drugs and novel Ube3a mutants:
Monica Sonzogoni, Centre for Neurodevelopmental Disorders, Dept of Neurosciences, Erasmus MC, Netherlands
This group previously described the characteristics/phenotypes of AS, and their work now focused on testing the robustness of these characteristics using a battery of behaviour tests. It was pointed out that there are important clinical questions to focus on including: information on meaningful outcome measures, assessment of the characteristics and various interventions.
A conclusion from this work was that the AS mouse model can be used to assess the majority of the shared AS characteristics except the absence of speech, providing confirmation that AS characteristics can be identified, can be put into a mouse model and can be used for drug testing.

Cellular phenotypes of human AS iPSC derived neurons
Stormy Chamberlain, Dept of Genetics and Genome Sciences, UConn Health, USA
This work focused on stem cell derived human neurons and characterisation of neurons generated from people with AS. It aimed to understand neuronal maturation and seeing whether specific phenotypes could be made from human AS neurons. One of the key reasons for doing this work was to help develop future therapies.
The generated neurons facilitated various studies, used to assess whether specific mutations/changes in Ube3a are likely to cause AS and whether therapeutic approaches can successfully restore neuronal function.
*iPSC – induced Pluripotent Stem cell culture are those generated from adult cells. Pluripotent stem cell are master cells. They can potentially produce any cell or tissue the body needs to repair itself. This “master” property is called pluripotency.
*Phenotype is the set of observable characteristics of an individual resulting from the interactions of its genes or genotype with the environment.

Potential therapeutic approach for synaptic deficit in AS – the JNK inhibitor peptide (human in vitro model)
Tiziano Borsello, IRCCS Cytogenetics and Molecular Genetics Lab, Istito Auxologico Italiano, Milano, Italy
This work focused on the role of JNK at the nerve synapse. It is known that Ube3a loss impairs synaptic transmission but the mechanism involved needs to be further understood. Early data from this work shows that differences exist between samples from people with AS and controls (i.e. non-AS). JNK plays a significant role and works by controlling a number of cellular processes including proliferation, embryonic development and apoptosis. It is thought that differences observed in AS group between the males and females may be due to hormonal differences.
*Apoptosis is the death of cells as a normal and controlled part of development and growth.
*JNK, c-jun N terminal kinase, a group of enzymes which play an important an important role in the regulation of neuronal functions. *
*Synapses is a structure that allows a nerve cell to pass an electrical or chemical signal to another nerve.

AS treatment opportunities and clinical biomarkers
Ben Philpot, University of North Carolina, USA
This work focused on ‘Epiloptogenesis’ which is the serialisation of seizures i.e. the gradual process of becoming more susceptible to seizures. Using mice, they showed that the loss of Ube3a from GABAergic neurons (inhibitory neurons) increased seizure sensitivity which was not observed in glutamerigic neurons (excitatory neurons).
Tests carried out using mice showed similar susceptibility in early stages of the experiments, with larger differences observed in the later stages in the normal vs the AS mice (greater susceptibility in AS neurons). They also used a hyperthermia induced seizure model where it was observed that seizures occur at much lower temperatures in the AS mice than in normal mice.
A very interesting piece of work gave the results of deleting ube3a in excitatory and inhibitory neurons followed by their reinstatement, helping to understand the reversibility of the epiloptogenesis. Reinstatement of ube3a reduced susceptibility in juvenile mice which was not seen in adult AS.

GABA mediated inhibitory dysfunction and its pathophysiological contribution in AS
Kiyoshi Egawa, Pediatric Dept., Hokkaido University Graduate School of Medicine, Japan
Analysis of the somatosensory evoked response using magnetoencephalography was performed and shown to be modified by GABAa receptor agonists. The total amount of GABAa receptor is not decreased in people AS. Tonic inhibition is different in different parts of the brain and maybe due to the GAT1 (GABA transporter 1). Dysregulation of tonic inhibition is a potential target for developing pharmacological strategy for AS.

*Tonic inhibition is a constant, long-lasting inhibition which is in contrast with phasic inhibition describing short intermittent bursts of inhibition. Recently, gain, rather than loss, of tonic inhibition has been shown to underlie the pathophysiology of epilepsy.
*Somatosensory is a part of the sensory nervous system which is made up a sensory neurons and pathways.
Cannabidiol extract as a new approach in the anticonvulsive treatment of the Angelman Syndrome – based on neurotransmitter profile, particularly in consideration of GABA and glutamate

Christel KannegieBer-Leitner, Research Group Angelman e.V., Germany
This presentation focused on the use cannabidiol extract (CBD) in AS a potential new approach.

Details of experience with a young man, the son of Christel, with AS and NCSE (Non-Convulsive Status Epilepticus) who had immediate freedom from seizures for 8 months after treatment with CBD.
A stronger glutamate was found in Magnesium (Osborn et al., The Journal of Clinical Pharmacology, 2016, 56(3) 260-265). The experience was that irregular use of Magnesium could be useful. However, questions remain on both these approaches and research is needed to understand long- and short-term side and also the role that genetics may play.

Imprinting defects and differential diagnosis
Bernhard Horsthemke, Jasmin Beygo and Karin Buiting Universitatsklinikum, Essen, Germany
This presentation focused on the imprinting defects and differential diagnoses within the family of AS syndromes.
Adeno Associated Virus Mediated Ube3a gene or protein replacement strategies
Ed Weber, Molecular Pharmacology and Physiology, CSO Byrd Alzheimer’s Institute, USA and also for AGILIS Biotherapeutics, USA
This talk focused on a gene therapy shown to restore learning and memory in a mouse model. This group previously showed a recovery in spatial and associated memory defects as well as the underlying alteration in hippocampal synaptic plasticity following the use of “Adeno Associated Virus” also known as AAV to deliver either the ube3a protein or gene.
This work is advancing and the current focus is on bioavailability. The phase I clinical trial protocol is being worked on however it needs good outcome measures but plans to be active for late 2020.
*Bioavailability is the proportion of a drug or other substance which enters the circulation when given to an individual and able to have effect.
Potential therapeutic approach for synaptic deficit in AS: the JUNK peptide (mouse model in vivo)

Silvia Russo, Neuronal Death and Neuroprotection Lab, Dept of Pharmacological and Biomolecular Sciences, CEND, Milano, Italy
Potential therapeutic approach for synaptic deficit in AS with the aim of creating a patient specific model to detect biomarkers (morphological biochemical ad functional biomarkers).
Natural history study efforts in the AS and the scientific rationale for therapy with antisense oligonucleotides

Rebecca Crean, Director, Clinical Development, IONIS, USA
IONIS are working on anitsense oligonucleotide (ASO) therapy as a platform and focused on AS to unsilence a protein. IONIS are working on a large number of ASOs for activity in multiple tissues. ASOs do not cross the blood brain brain so administration is via bolus intra-thecal injections. In AS paternal ube3a is silenced, using an ASO this could be unsilenced and therefore could be a novel approach to treat AS.
Foundational science needs to enable feasible efficient drug development and assist in the understanding the impact on the individual patient measures including patient reported outcomes will be very important.
IONIS is focused on developing natural history studies which will facilitate drug development. Natural history studies are studies on individuals over time who have or are at risk of developing a specific medical condition. They allow door greater understanding of the disease and help guide clinical trials. The main gaps in knowledge are longitudinal changes, biomarkers, correlation between ube3a levels and clinical features. A number of international registries exist which assist including the following, Backpackhealth.com, AS registry, China Angelman registry, and Angelman Biomarkers and Outcomes Measures (ABOM).

*Anti-sense oligonucleotides are short, synthetic, single-stranded DNA (that can alter protein production.
*Intra-thecal is a route of administration for drugs via an injection into spinal cord

OVID Therapeutics: Update on the AS STARS: Topline results from a phase 2 adults and adolescent AS clinical trial. A randomised, double blind, safety and efficacy study of Gaboxadol (OV101)
Amit Rakhit, Chief Medical and Portfolio Officer, OVID Therapeutics, USA.
This presentation focused on the development work that OVID are focused on in particular the STARS clinical trial using OV101. OV101 is a selective GABAa receptor agonists which was tested in this phase II study in 3 groups I.e. placebo, once daily dosing and twice daily dosing (10mg, 15mg).
A total of 88 peope with AS were recruited to the study and assessments completed included were adverse events, global symptoms, behaviour scales and sleep diaries.
The primary endpoint of the study was met in that the agent was safe and tolerable as measured by the adverse events. Some exploratory end points were assessed at 12 weeks with global functioning AS assessed by a Clinician Global Impression-improvement (CGI-I) was statistically different between placebo and the treatment groups, with a 27.4% difference being reported.
It is recognised in their studies that behaviour scales need to be altered to consider non-verbal nature of AS. Additional data is presented in 2 weeks at the international conference for American Academy of Child and Adolescent Psychiatry.