Scientists publish first complete record of genetic mutations behind rare vascular disease

Human anatomy - heart

The genetic architecture of a debilitating and potentially fatal vascular disease has for the first time been detailed in its entirety, providing clinicians with the comprehensive data needed to improve diagnosis and deliver more personalised patient care.

Scientists investigating Pulmonary Arterial Hypertension (PAH) have compiled the most up to date and complete record of all the defective variations found in the genes that cause the disease.

The new study, led by Dr Rajiv Machado from the University of Lincoln, UK, draws together the complete genetic information of hundreds of individuals affected by PAH. This advance will not only offer new opportunities to identify the mutation which causes PAH in individual patients but will also provide an important tool to correlate genetic data, allowing for more tailored approaches to the clinical management of the disease. It has been published in the online academic journal Human Mutation.

PAH is an often fatal disorder resulting from several causes, including an assortment of genetic defects. It is a progressive disease characterised by abnormally high blood pressure (hypertension) in the pulmonary artery, the blood vessel that carries blood from the heart to the lungs. Symptoms are shortness of breath, dizziness, swelling (oedema) of the ankles or legs, chest pain and a racing pulse.

Heritable PAH leads to a chronic elevation of pulmonary arterial pressure, which can result in heart failure.

While mutations in a gene called BMPR2 are the single most common cause for hereditary cases, mutations capable of causing disease have been observed in approximately 25 per cent of patients without a prior family history of disease.

The new study, which brings together data from specialist PAH centres based in Germany, France, North America and the UK,  describes molecular genetic analyses of the 10 functionally characterised genes that cause PAH and provides a compilation of all mutations identified to date.

It also describes an additional 370 independent mutations of BMPR2 in patients, either previously excluded from or identified since the last comprehensive mutation update by Dr Machado and colleagues in 2009. Of these, 81 are new variations.

Dr Machado, from the University of Lincoln’s School of Life Sciences, said: “This is the most comprehensive and complete compilation of all defective variations in the genetic risk factors for PAH. This will allow the clinical geneticists, with a greater degree of certainty, to conclude that the gene variations present in a patient are either disease causing or of unknown significance. This could inform a patient’s decisions about starting a family or undertaking pre-natal testing. Prior to this a clinician would have to try and understand genetic data received for a single patient by trawling through historic manuscripts to make a diagnosis. This report has the potential to be of great importance to the diagnostic centres around the world.

“The continuing identification of genetic factors, as explored in this paper, provides unique insight to the genetic mechanisms driving disorders of pulmonary vascular function. These data provide a key resource in data interpretation and how these genetic insights may lead to the potential discovery and delivery of novel targeted therapeutic options in PAH.”

This important resource of clinical and scientific data has now been posted on a freely available public repository, namely ClinVar, and will be accessible through Dr Machado’s Lincoln profile page.

The emergence of next-generation sequencing (NGS) allows scientists to sequence much more quickly and cheaply, and as such has revolutionised the study of genomics and molecular biology. NGS has allowed researchers to identify novel, rare genetic variations in the PAH disease spectrum, detailed in this study. It is likely that future avenues will include the use of more NGS technologies, the pinnacle of which is whole-genome sequencing – a process that determines the complete DNA sequence of an organism’s genome at a single time.

Breakthrough for debilitating heart and lung disease

British Heart Foundation logo British Heart Foundation logo A protein that targets the effects of a faulty gene could offer the first treatment targeting the major genetic cause of Pulmonary Arterial Hypertension (PAH), according to research funded by the British Heart Foundation (BHF).

Genetic evidence dating back to 2000, from research the BHF helped to fund, indicated that the absence or reduced activity of a particular protein, bone morophogenetic protein type II receptor (BMPR-II), leads to PAH. BMPR-II is important to the normal function of the blood vessels of the lungs. PAH is thought to affect around 6,500 people in the UK.

This new study led by BHF Professor of Cardiopulmonary Medicine Nick Morrell and including expertise from Dr Rajiv Machado at the University of Lincoln, UK, is the first to use a protein, called BMP9, to reverse the effects of reduced activity of BMPR-II and to reverse the disease itself. The study was conducted in mice and rats, but also using cells from patients with PAH. It is published today in Nature Medicine.

PAH is a chronic and debilitating disease that affects the blood vessels in the lungs, leading to heart failure, and leaves sufferers feeling breathless and exhausted. Current treatments only target the symptoms and prognosis remains poor. The only effective cure is a lung, or heart and lung, transplant, which has associated risks and complications.

Once diagnosed with PAH, a person has a 30 per cent chance of dying within three years and the condition affects more women than men. Researchers speculate that this gender disparity is caused by pregnancy triggering the disease in genetically susceptible women or that oestrogen can affect the function of BMPR-II.

A team at the University of Cambridge, with contributions from researchers at the University of Lincoln, Switzerland and the US, searched for a BMP protein that could enhance the function of BMPR-II to target the condition. The researchers firstly trialled different BMP proteins on lung blood vessel cells grown in a dish. This process showed BMP9 to be most selective, and therefore less likely to have negative effects on other cells.

This study used the first animal model, a mouse, which closely mimics the human genetic form of the disease. The University of Lincoln’s Dr Machado was instrumental in designing the strategy for development of this experimental model employed in the study.

Using a specific set of molecular tools, Dr Machado replicated a mutation frequently observed in human PAH patients which, subsequently, was introduced into the mouse genome. This facilitated the generation of a mouse model that naturally mirrored the human disease state critical for the assessment of therapeutic options.

Ultimately, the team showed that BMP9 treatment reversed PAH in three separate mouse and rat models. They found that the treatment works in mice with both the genetic from of the disease, and in acquired forms of PAH, where the cause is unknown.

BHF Professor Nick Morrell, who led the research, from the Department of Medicine at the University of Cambridge School of Clinical Medicine, and Director of the BHF Cambridge Centre for Cardiovascular Research Excellence, said: “The next step for our research is studies in people with pulmonary arterial hypertension – first, safety testing to ensure the compound can be given to people. But we’re confident of passing this phase because BMP9 exists naturally in the body. We’re just giving patients more of it.”

Professor Jeremy Pearson, Associated Medical Director of the British Heart Foundation, which funded the research, said: “We’re very excited by these results. This condition is horrible and an effective treatment that prevents the need for a transplant would be a game-changer. Clinical trials of the treatment in patients are still needed but these findings, from years of research supported by the BHF, offer real promise of a cure.”

​Student awarded specialist equipment

 

A Biomedical and Medical Sciences student has won more than £3,000 worth of specialist equipment and training

PhD Student Anastasios Karountzos, who was nominated by supervisor Dr Rajiv Machado, was one of just 20 winners chosen for the 2014 Gold Sponsored Student programme by Primerdesign Ltd.

He will receive qPCR kits (quantitative polymerase chain reaction), which is a laboratory technique used to amplify and simultaneously quantify a targeted DNA molecule.

Dr Machado, from the School of Life Sciences, University of Lincoln, UK, said: “In the context of disease this is important to understand the effect of identified mutations and, also, the potential deregulation of gene/protein networks affected by the initial mutational defect. In our work, three independent projects will benefit greatly from this award based around pulmonary vascular disease.”

Overall 20 ‘Gold’ level sponsorships were awarded this year to research students in various institutions across the UK.

On receiving the award, Anastasios said: “I feel honoured that our research group has been selected for this generous sponsorship from Primerdesign, which will provide us with professional support and training in qPCR based experiments from experts in the field.”

Primerdesign will also be offering to present two seminars which will be available to the whole institution.

These seminars, given by qPCR experts, will demonstrate ways for life scientists at the University of Lincoln to improve standards in their real-time PCR experiments and generate better quality data.

Dr Jim Wicks, Managing Director Primer said: “We aim to help qPCR students obtain the best possible data from their experiments and publish in accordance with the MIQE guidelines. Being former researchers ourselves we want to make qPCR as painless as possible and give something back to fellow students.”

Primerdesign is a successful spin-out from the University of Southampton. They specialise in the supply of assays, kits and reagents for use in real-time PCR.​

Step forward in understanding arterial disease

Further strides have been made into isolating the origin of cells that could lead to a greater understanding of what goes into the development of our blood circulating systems.

University of Lincoln Life Sciences academic Dr Rajiv Machado, with colleagues from the University of Cambridge, King’s College London and Papworth Hospital, has revealed the recent findings in a research letter to The American Journal of Respiratory and Critical Care Medicine.

Dr Machado’s main research area is in Pulmonary Arterial Hypertension (PAH) which is a progressive disorder characterised by abnormally high blood pressure (hypertension) in the pulmonary artery, the blood vessel that carries blood from the heart to the lungs. Symptoms are shortness of breath, dizziness, swelling (oedema) of the ankles or legs, chest pain and a racing pulse.

In this latest study, researchers investigated genetically identical twins, both of which had the genetic marker responsible for PAH. However, only one had the disorder which resulted in both a heart and lung transplant.

From this starting block, the team were able to investigate the origin of blood outgrowth endothelial cells (BOEC), which are stem cells and good candidates for vascular (re-) generating cell therapy. However, uncertainty remains as to the specific origin of these cells.

The researchers study of the twins and the mutation they both harboured enabled them to identify a marker to show that those stem cells, the BOECs, were very unlikely to have come from the heart or lungs.

Dr Machado said: “When the circulating BOECs were cultured from the new heart and lungs they still showed the mutation. Hence, they must have been produced in a different organ/s. The importance of this is that scientists are keen to know the origin of these cells both as a proxy for basic science and to provide an understanding of what goes into the development of our blood circulating systems. If we can in one fell swoop remove two organs as being contributory then we are another step closer to knowing where these cells come from.”