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Liverpool Identifying Genetic Defects in Glaucoma

Forensics

Scientists from the University of Liverpool have sequenced the mitochondrial genome in glaucoma patients to help further understanding into the genetic basis for the disease.

Glaucoma is a major cause of irreversible blindness, affecting more than 60 million people worldwide, increasing to an estimated 79.6 million people by 2020. It is thought that the condition has genetic origins and many experiments have shown that new sequencing approaches could help understand how the condition develops.

Studies on primary open-angle glaucoma - the most common form of glaucoma - have shown that mutations in mitochondria, the energy generating structures in all cells, could give valuable insight into how to prevent the disease.

Using new gene sequencing techniques, called massively parallel sequencing, the Liverpool team have produced data on the mitochondrial genome taken from glaucoma patients from around the world.

The impact that mitochondrial gene change has on disease progression has been difficult to fully determine as cells in the human body can contain mixtures of healthy and mutated mitochondrial genes. Using this new technology, however, the researchers aim to support the delivery of  personalised medicines to identify drugs that will target mutated mitochondria.

Professor Colin Willoughby, from the University’s Institute of Ageing and Chronic Disease, explains: “Understanding the genetic basis of glaucoma can direct care by helping to determine the patient's clinical risk of disease progression and visual loss.

“Increasing evidence suggests that mitochondrial dysfunction results in glaucoma and drugs that target mitochondria may emerge as future therapeutic interventions.

“Further studies on larger glaucoma numbers of patients are required to firmly establish the link between genetic defects in the mitochondrial genome and glaucoma development.

“Our research, however, has demonstrated that massively parallel sequencing is a cost-effective approach to detect a wide spectrum of mitochondrial mutations and will improve our ability to understand glaucoma, identify patients at risk of the disease or visual loss and support the development of new treatments.”

The research is published in Genetics Medicine and supported by the British Council for the Prevention of Blindness.

In a separate study, the research team in Liverpool are also analysing microRNAs in glaucoma, funded by Fight for Sight and The International Glaucoma Association. The research aims to uncover what role microRNAs play in regulating the eye’s drainage system.

The eye maintains a constant pressure by continuously producing fluid (called aqueous humour) while an equal amount of the fluid drains out of the eye through what is known as the trabecular meshwork. In the most common type of glaucoma, the trabecular meshwork becomes blocked slowly over time. As pressure in the eye mounts the optic nerve becomes damaged, leading to serious, irreversible sight loss if left untreated.

It is known that complex networks of microRNAs control whether proteins are produced or destroyed in the body, both in health and disease. In the healthy trabecular network microRNAs are involved in cell death and how the tissue responds to mechanical stress and scarring. It is not known, however, which microRNAs might play a part in primary open-angle glaucoma or which proteins they control.

Professor Colin Willoughby said “We plan to assess the microRNA genes in tissue from patients undergoing surgery for glaucoma and compare this with normal trabecular meshwork tissue.

“We will use the latest microarray technologies to assess over 2000 microRNAs in a global fashion to understand which microRNAs are linked with glaucoma. From this list we will validate the best candidates and use computer models to identify the genes and proteins they control.”

Results from the project should give significant insight into some of the key molecules involved in glaucoma. They could also help advance the emerging field of microRNA therapeutics, in which microRNA mimics or blockers against specific targets could be developed to lower eye pressure as new treatments for glaucoma. In the area of microRNA therapeutics, they have funding from the National Centre for the Replacement Refinement & Reduction of Animals in Research (NC3R) to develop an organ culture system of glaucoma in which part of a human donor eye is maintained in the laboratory to test these new miRNA therapies.

In a timely follow up to the research publication, scientists and consultants from The University of Liverpool and St Paul’s Eye Unit have got together to create an exhibition exploring the human eye at Liverpool Town Hall.

Doctors and scientists from St Paul’s and the University’s Department of Eye and Vision Science will be talking to visitors about the latest technologies and techniques being used to identify and treat eye conditions and showing them how the state-of-the-art equipment at St Paul’s is used. St. Paul’s Eye Unit dates back to 1871 and is regarded globally as a centre of excellence for care, research and education. Over 100,000 patients visit St. Paul’s Eye Unit each year.

Professor Simon Harding, from the University’s Institute of Ageing and Chronic Disease and Chair of Clinical Ophthalmology at St Paul’s Eye Unit, said: “St Paul’s has always had a huge amount of support from the local community and, as part of the Freedom of the City programme, we wanted to host an event for members of the public to allow them to discover more about the eye, meet the team, and see first-hand some of the groundbreaking work performed at the University. “This is a rare opportunity for people to explore first-hand the world of ophthalmology in a unique environment.”

The official Freedom of the City ceremony for St Paul’s Eye Unit will be presented by The Lord Mayor, Cllr Erica Kemp CBE. The accolade is recognised as ‘the highest nomination that can be bestowed to an organisation that has rendered significant and valuable service to the City.