A consortium led by the Royal College of Surgeons in Ireland (RCSI) has secured €11.5 million (US$15.4 million) in funding from the European Commission (EC) to build a comprehensive picture of microRNA (miRNA) biology in patients with epilepsy.

The group hopes to identify new miRNA drug targets that could form the basis of future therapies and to develop miRNA-based diagnostic methods for identifying molecular signatures of the condition and for monitoring patient responses to therapy.

The EpimiRNA consortium, which is funded under the EC’s 7th Framework Program (FP7), involves 11 academic institutes across eight countries, including the U.S. and Brazil, plus another six European biotechnology firms.

The partners will build on early observations indicating that miRNA species may have a causal role in the development of epilepsy, with a particular focus on temporal lobe epilepsy. “It’s designed to be a fresh, almost unbiased look,” project coordinator David Henshall, of the Dublin-based RCSI, told BioWorld Today.

The group will sequence the miRNA genome – encoding some 1,500 individual miRNA species, plus associated proteins – of about 1,000 patients to determine whether they exhibit any unique features. The consortium will also study tissue samples taken from severely drug-resistant patients undergoing surgery, in order to identify all functional miRNA species, using a method called high-throughput sequencing of RNA isolated by crosslinking immunoprecipitation (HITS-CLIP).

Many studies at present involve a global view of all miRNA molecules present within a given cell or tissue sample. The HITS-CLIP technique will enable the research consortium to identify only those species that are bound to argonaut proteins, which are required to mediate miRNA-based gene silencing.

The consortium also will conduct clinical studies with patients in order to identify possible blood-based miRNA signatures of the disease. “MicroRNAs seem to circulate in the bloodstream in a stable form,” said Henshall. Any such molecular correlates of the disease could be a useful guide to monitoring responses to therapy. “There’s a lot of trial and error with finding the right drug for an epileptic patient,” he said. Moreover, many patients are not well served by present anti-convulsant therapies. “There’s a significant drug-resistance problem in epilepsy,” Henshall said.

As well as screening for new molecules implicated in epilepsy, the partners will also study early leads in parallel. For example, Henshall has obtained preliminary evidence which suggests that miRNA-134 may contribute to the pathogenesis of the condition. Blocking it with an antagomir elicited a pronounced effect in experimental mice. “It really reduced seizures in our animal models,” he said.

Consortium member Gerhard Schratt, of Philipps University Marburg, in Germany, recently published a paper indicating that miRNA-134, under the control of a DEAH-box helicase enzyme called DHX36, localizes to the dendrites of hippocampal neurons, where it influences the size of dendritic spines, the dynamic, bulbous projections that play a key role in synaptic plasticity. The study, titled “The DEAH-box helicase DHX36 mediates dendritic localization of the neuronal precursor-microRNA-134,” appeared in the May 1, 2013, issue of Genes & Development.

Henshall and colleagues have also previously reported that tissue samples from drug-resistant patients with hippocampal sclerosis, a common feature of temporal lobe epilepsy, have major reductions in levels of mature miRNAs compared with tissue samples from autopsy controls. They proposed that this effect is due to loss of Dicer, the RNAse III enzyme involved in miRNA processing. The findings are reported in a paper, titled “Reduced Mature MicroRNA Levels in Association with Dicer Loss in Human Temporal Lobe Epilepsy with Hippocampal Sclerosis,” which was published online in PLOS One on May 15, 2012.

Felix Rosenow, also of Philipps University Marburg, another early European leader in studying the role of miRNA in epilepsy, is co-coordinator of the consortium. The influential population geneticist David Goldstein, of Duke University, in Durham, N.C., also is involved.