Antagomir-134 as a Novel Therapeutic for Angelman Syndrome

Angelman syndrome is characterised by cognitive impairment with profound speech delay, motor impairments and ataxic-like symptoms, EEG abnormalities and drug-resistant epilepsy. It is caused by the loss of function of the ubiquitin ligase 3A (UBE3A) gene. UBE3A contains three transcripts, two of which are translated to protein, and the third transcript, Ube3a1 is untranslated and contains 3’ untranslated regions. Ube3a1 contains a binding site for a large microRNA (miRNA) cluster, miR-379~410 cluster. The miR-379~410 cluster contains multiple miRNAs that are involved in neuronal morphology and brain development, including miR-134, thus miRNA dysregulation could be involved in the pathophysiology of AS. We have hypothesised that loss of UBE3A in AS, results in loss of the miRNA sponge, which leads to an increase of miR-134 and a downregulation of its targets.

Here, we sought for the first time functionally assess miR-134 role in a model of paediatric status epilepticus (SE) by using antagomir-134 (Ant-134). Then, we characterised a mouse model of AS using the Ube3a ^(m-/p+) model. Finally, we attempted to use Ant-134 to treat the most relevant AS-like phenotypes.

The first results chapter investigates the role of miR-134 in a paediatric model of SE. Seizures were induced in 21 day old mice (P21) using a systemic injection of kainic acid. We then demonstrate that Ant-134 has seizure suppressive effects in this model. In addition, Ant-134 blocked the initiation of SE in a number of mice, in comparison to SE induced in all mice that received the scramble-control compound. We also found neuroprotective effects of Ant-134 in the CA3 region of the hippocampus.

In results chapter two, we characterised a mouse model of AS using the Ube3a ^(m-/p+) model. This model recapitulated multiple symptoms associated with AS including an abnormal EEG, motor impairments in the open field and rotarod, deficits in marble burying and increased seizure susceptibility using chemoconvulsant agents and the induction of audiogenic seizures. This was done using two generations of mice, F1 for EEG analysis and behaviour and N4 for the induction of audiogenic seizures.

The final results chapter aimed to use Ant-134 to treat the above phenotypes. Ant-134 significantly reduced audiogenic seizures in both P21 and in adult mice. Furthermore, Ant-134 restored motor phenotypes in the open field. Due to the complexity of the syndrome, we believe a disease-modifying therapy would highly benefit from a “multi-target combined approach”. Thus, we used small RNA sequencing and identified a number of miRNAs from the miR-379~410 cluster that were differentially expressed in these mice, and potentially could be used as an adjuvant to Ant-134.

In summary, these data provide strong evidence for miRNA dysregulation in AS. Ant-134 can be used to treat multiple symptoms of AS.