Researchers have explored the role of a master gene that controls the functioning of other genes involved in heart development. Variations in this gene – NR2F2 – are responsible for the development of severe forms of congenital heart disease.
Approximately one per cent of all babies are born with congenital heart disease, where the normal workings of the heart are affected. Because the damage to the heart is structural, most babies will need surgery to correct the problem. Although genetic causes are known to underlie the disease, these causes are not very well understood.
Scientists have previously shown that mice with a less active NR2F2 gene had abnormal heart development. To see if the gene was involved in severe forms of human congenital heart disease, the team looked at DNA sequences of parents and affected children and found that variation on the NR2F2 caused the structural damage that underlies these conditions.
The team found that these genetic variants were typically only present in the child and not the parents, revealing that congenital heart disease producing variants occur in the womb.
‘What we see is that these rare variants in the NR2F2 gene interfere with the normal heart development and cause severe forms of congenital heart disease during human development,’ says Saeed Al Turki, first author from the Wellcome Trust Sanger Institute.
NR2F2 is a master regulator for other genes involved in the development of a healthy functioning heart – once the activity of NR2F2 is affected it has a knock-on effect on these other genes affecting the healthy development of the heart.
The team found that different types of damage in the NR2F2 gene cause different types of heart defects. Genetic variants that completely deactivate the NR2F2 gene tended to cause damage to the left side of the heart. In contrast, genetic variants that alter activity of the gene but do not deactivate it more commonly caused a specific sub-type of holes in the hearts of patients. Wellcome Trust Sanger Institute

Extreme and traumatic events can change a person – and often, years later, even affect their children. Researchers of the University of Zurich and ETH Zurich have now unmasked a piece in the puzzle of how the inheritance of traumas may be mediated.
The phenomenon has long been known in psychology: traumatic experiences can induce behavioural disorders that are passed down from one generation to the next. It is only recently that scientists have begun to understand the physiological processes underlying hereditary trauma. ‘There are diseases such as bipolar disorder, that run in families but can’t be traced back to a particular gene’, explains Isabelle Mansuy, professor at ETH Zurich and the University of Zurich. With her research group at the Brain Research Institute of the University of Zurich, she has been studying the molecular processes involved in non-genetic inheritance of behavioural symptoms induced by traumatic experiences in early life.

Mansuy and her team have succeeded in identifying a key component of these processes: short RNA molecules. These RNAs are synthesised from genetic information (DNA) by enzymes that read specific sections of the DNA (genes) and use them as template to produce corresponding RNAs. Other enzymes then trim these RNAs into mature forms. Cells naturally contain a large number of different short RNA molecules called microRNAs. They have regulatory functions, such as controlling how many copies of a particular protein are made.

The researchers studied the number and kind of microRNAs expressed by adult mice exposed to traumatic conditions in early life and compared them with non-traumatised mice. They discovered that traumatic stress alters the amount of several microRNAs in the blood, brain and sperm – while some microRNAs were produced in excess, others were lower than in the corresponding tissues or cells of control animals. These alterations resulted in misregulation of cellular processes normally controlled by these microRNAs.

After traumatic experiences, the mice behaved markedly differently: they partly lost their natural aversion to open spaces and bright light and had depressive-like behaviours. These behavioural symptoms were also transferred to the next generation via sperm, even though the offspring were not exposed to any traumatic stress themselves.

The metabolism of the offspring of stressed mice was also impaired: their insulin and blood-sugar levels were lower than in the offspring of non-traumatised parents. ‘We were able to demonstrate for the first time that traumatic experiences affect metabolism in the long-term and that these changes are hereditary’, says Mansuy. The effects on metabolism and behaviour even persisted in the third generation.

‘With the imbalance in microRNAs in sperm, we have discovered a key factor through which trauma can be passed on,’ explains Mansuy. However, certain questions remain open, such as how the dysregulation in short RNAs comes about. ‘Most likely, it is part of a chain of events that begins with the body producing too much stress hormones.’

Importantly, acquired traits other than those induced by trauma could also be inherited through similar mechanisms, the researcher suspects. ‘The environment leaves traces on the brain, on organs and also on gametes. Through gametes, these traces can be passed to the next generation.’

Mansuy and her team are currently studying the role of short RNAs in trauma inheritance in humans. As they were also able to demonstrate the microRNAs imbalance in the blood of traumatized mice and their offspring, the scientists hope that their results may be useful to develop a blood test for diagnostics. ETH Zurich

Johns Hopkins Kimmel Cancer Center investigators report they have designed a blood test that accurately detects the presence of advanced breast cancer and also holds promise for precisely monitoring response to cancer treatment.
The test, called the cMethDNA assay, accurately detected the presence of cancer DNA in the blood of patients with metastatic breast cancers up to 95 percent of the time in laboratory studies.
Currently, there is no useful laboratory test to monitor patients with early stage breast cancer who are doing well, but could have an asymptomatic recurrence, says Saraswati Sukumar, Ph.D., who is the Barbara B. Rubenstein Professor of Oncology and co-director of the Breast Cancer Program at the Johns Hopkins Kimmel Cancer Center. Generally, radiologic scans and standard blood tests are indicated only if a woman complains of symptoms, such as bone aches, shortness of breath, pain, or worrisome clinical exam findings. Otherwise, routine blood tests or scans in asymptomatic patients often produce false positives, leading to additional unnecessary tests and biopsies, and have not been shown to improve survival outcomes in patients with early stage breast cancer who develop a recurrence.
Sukumar, also a professor of pathology at Johns Hopkins, says that the current approach to monitoring for recurrence is not ideal, and that ‘the goal is to develop a test that could be administered routinely to alert the physician and patient as soon as possible of a return of the original cancer in a distant spot. With the development of cMethDNA, we’ve taken a first big step toward achieving this goal.’
To design the test, Sukumar and her team scanned the genomes of primary breast cancer patients, as well as DNA from the blood of metastatic cancer patients. They selected 10 genes specifically altered in breast cancers, including newly identified genetic markers AKR1B1, COL6A2, GPX7, HIST1H3C, HOX B4, RASGRF2, as well as TM6SF1, RASSF1, ARHGEF7, and TMEFF2, which Sukumar’s team had previously linked to primary breast cancer.
The test, developed by Sukumar, collaborator Mary Jo Fackler, Ph.D., and other scientists, detects so-called hypermethyation, a type of chemical tag in one or more of the breast cancer-specific genes present in tumour DNA and detectable in cancer patients’ blood samples. Hypermethylation often silences genes that keep runaway cell growth in check, and its appearance in the DNA of breast cancer-related genes shed into the blood indicates that cancer has returned or spread.
In one set of experiments, the researchers tested the assay’s ability to detect methylated tumor DNA in 52 blood samples – 24 from patients with recurrent stage IV breast cancer and 28 from healthy women without breast cancer, and again in blood samples from 60 individuals – 33 from women with all stages of breast cancer and 27 from healthy women. In each case, the blood test was up to 95 percent accurate in distinguishing patients with metastatic breast cancer from healthy women.
The investigators also studied the assay’s potential to monitor response to chemotherapy. They evaluated 58 blood samples from 29 patients with metastatic breast cancer, some taken before the initiation of therapy and some taken 18 to 49 days after starting a new chemotherapy regimen. In as little as two weeks, they report, the test detected a significant decrease in DNA methylation in patients with stable disease or in those who responded to treatment; this decrease was not found in patients whose disease progressed or who did not respond to treatment.
‘Our assay shows great potential for development as a clinical laboratory test for monitoring therapy and disease progression and recurrence,’ Sukumar says. If it’s determined early that a treatment is not working, clinicians can save time and switch to a different therapy, she says.
In addition, the researchers tested the gene panel used in the cMethDNA assay against samples from The Cancer Genome Atlas, a catalog of genes in various cancer types, finding that the gene panel may also be useful in detecting recurrent lung or colorectal cancers but not as accurate in detecting recurrent ovarian, kidney or stomach cancers. Johns Hopkins Kimmel Cancer Center

Researchers from Yale School of Medicine and Celera Diagnostics have confirmed and extended the significance of a genetic variant that substantially increases the risk of a frequently fatal thoracic aortic dissection or full rupture.
Thoracic aortic aneurysms, or bulges in the artery wall, can develop without pain or other symptoms. If they lead to a tear — dissection — or full rupture, the patient will often die without immediate treatment. Therefore, better identification of patients at risk for aortic aneurysm and dissection is considered essential.
The research team, following up on a previous genome-wide association study by researchers at Baylor College of Medicine, investigated genetic variations in a protein called FBN-1, which is essential for a strong arterial wall. After studying hundreds of patients at Yale, they confirmed what was found in the Baylor study: that one variation, known as rs2118181, put patients at significantly increased risk of aortic tear and rupture. In addition, the Yale team was able to show that this increased risk of tear was powerful enough to be significant even independently of aortic size.
‘Although surgical therapy is remarkable and effective, it is incumbent on us to move to a higher genetic level of understanding of these diseases,’ said senior author Dr. John Elefteriades, the William W. L. Glenn Professor of Surgery (Section of Cardiac Surgery) at Yale School of Medicine, and director of the Aortic Institute at Yale-New Haven Hospital. ‘Such studies represent important steps along that path.’
The researchers hope their confirmation of the earlier study may help lead to better clinical care of patients who may be at high risk of this fatal condition. ‘Patients with this mutation may merit earlier surgical therapy, before aortic dissection has a chance to occur,’ Elefteriades says. Yale cardiothoracic surgeons will now begin assessing this gene in clinical patients with aneurysm disease. Yale University

Large sections of the genome that were once referred to as ‘junk’ DNA have been linked to human heart failure, according to research from Washington University School of Medicine in St. Louis.
Molecules now associated with these sections of the genome are called non-coding RNAs. They come in a variety of forms, some more widely studied than others. Of these, about 90 percent are called long non-coding RNAs, and exploration of their roles in health and disease is just beginning.
Washington University investigators report results from the first comprehensive analysis of all RNA molecules expressed in the human heart. The researchers studied non-failing hearts and failing hearts before and after patients received pump support from left ventricular assist devices (LVAD). The LVADs increased each heart’s pumping capacity while patients waited for heart transplants.
‘We took an unbiased approach to investigating which types of RNA might be linked to heart failure,’ said senior author Jeanne M. Nerbonne, PhD, the Alumni Endowed Professor of Molecular Biology and Pharmacology. ‘We were surprised to find that long non-coding RNAs stood out. In fact, the field is evolving so rapidly that when we did a slightly earlier, similar investigation in mice, we didn’t even think to include long non-coding RNAs in the analysis.’
Heart failure refers to a gradual loss of heart function. The left ventricle, the heart’s main pumping chamber, becomes less efficient. Blood flow diminishes, and the body no longer receives the oxygen needed to go about daily tasks. Sometimes the condition develops after an obvious trigger such as a heart attack or infection, but other times the causes are less clear.
In the new study, the investigators found that unlike other RNA molecules, expression patterns of long non-coding RNAs could distinguish between two major types of heart failure and between failing hearts before and after they received LVAD support.
‘We don’t know whether these changes in long non-coding RNAs are a cause or an effect of heart failure,’ Nerbonne said. ‘But it seems likely they play some role in co-ordinating the regulation of multiple genes involved in heart function.’
Nerbonne pointed out that all types of RNA molecules they examined could make the obvious distinction: telling the difference between failing and non-failing hearts. But only expression of the long non-coding RNAs was measurably different between heart failure associated with a heart attack (ischemic) and heart failure without the obvious trigger of blocked arteries (non-ischemic). Similarly, only long non-coding RNAs significantly changed expression patterns after implantation of left ventricular assist devices.
Because of the difficulty in obtaining human heart tissue, the study’s sample size was relatively small, Nerbonne said. Her team analysed eight non-failing hearts, eight hearts in ischemic heart failure and eight hearts in non-ischemic heart failure. Though small, the study is unique because each of the 16 failing hearts was sampled twice, once before and once after LVAD support.
According to Nerbonne, this before-and-after sampling of heart tissue is an unusual feature of this study and one of its strengths. Cardiac surgeons first removed a sample of heart tissue while implanting the LVAD. Then, months later, transplant surgeons sampled the same failing hearts when each patient received a new donor organ. Previous studies comparing heart function before and after implanting a pump used samples taken from different patients.
This double sampling of the same organ is important for understanding what is happening on a molecular level to failing heart tissue when a pump literally takes some of the load off.
‘It’s clear that some patients experience a change in the structure and physiology of the heart tissue following pump support, and in some patients that change results in improved heart function,’ Nerbonne said. ‘One interesting question is whether these long non-coding RNAs could be a measure of whether the failing heart is getting better with an LVAD.’
Indeed, using the non-failing heart samples for comparison, about 10 percent of the long non-coding RNA expression that was disturbed in the failing hearts improved or returned to normal following LVAD support. While 10 percent may seem modest, only about 3 percent, at best, of other types of RNA expression returned to normal after pump support.
Nerbonne also is interested in exploring whether measures of long non-coding RNAs could be an early predictor of the disease, ideally before symptoms of heart failure even develop. Washington University School of Medicine in St. Louis