Some of the dramatic differences seen among patients with schizophrenia may be explained by a single gene that regulates a group of other schizophrenia risk genes.
The study revealed that people with schizophrenia who had a particular version of the microRNA-137 gene (or MIR137), tended to develop the illness at a younger age and had distinct brain features – both associated with poorer outcomes – compared to patients who did not have this version. This work was led by Drs. Aristotle Voineskos and James Kennedy.
Treating schizophrenia is particularly challenging as the illness can vary from patient to patient. Some individuals stay hospitalised for years, while others respond well to treatment.
‘What’s exciting about this study is that we could have a legitimate answer as to why some of these differences occur,’ explained Dr. Voineskos, a clinician-scientist in CAMH’s Campbell Family Mental Health Research Institute. ‘In the future, we might have the capability of using this gene to tell us about prognosis and how a person might respond to treatment.’
‘Drs. Voineskos and Kennedy’s findings are very important as they provide new insights into the genetic basis of this condition that affects thousands of Canadians and their families,’ says Dr. Anthony Phillips, Scientific Director at the Canadian Institutes of Health Research Institute of Neurosciences, Mental Health and Addiction.
Also, until now, sex has been the strongest predictor of the age at which schizophrenia develops in individuals. Typically, women tend to develop the illness a few years later than men, and experience a milder form of the disease.
‘We showed that this gene has a bigger effect on age-at-onset than one’s gender has,’ said Dr. Voineskos, who heads the Kimel Family Translational Imaging-Genetics Research Laboratory at CAMH. ‘This may be a paradigm shift for the field.’
The researchers studied MIR137 — a gene involved in turning on and off other schizophrenia-related genes — in 510 individuals living with schizophrenia. The scientists found that patients with a specific version of the gene tended to develop the illness at a younger age, around 20.8 years of age, compared to 23.4 years of age among those without this version.
‘Although three years of difference in age-at-onset may not seem large, those years are important in the final development of brain circuits in the young adult,’ said Dr. Kennedy, Director of CAMH’s Neuroscience Research Department. ‘This can have major impact on disease outcome.’
In a separate part of the study involving 213 people, the researchers used magnetic resonance brain imaging (MRI) and diffusion tensor-MRI (DT-MRI). They found that individuals with the particular gene version tended to have unique brain features. These features included a smaller hippocampus, which is a brain structure involved in memory, and larger lateral ventricles, which are fluid-filled structures associated with disease outcome. As well, these patients tended to have more impairment in white matter tracts, which are structures connecting brain regions, that serve as the information highways of the brain.
Developing tests that screen for versions of this gene could be helpful in treating patients earlier and more effectively.
‘We’re hoping that in the near future we can use this combination of genetics and brain imaging to predict how severe a version of illness someone might have,’ said Dr. Voineskos. ‘This would allow us to plan earlier for specific treatments and clinical service delivery and pursue more personalised treatment options right from the start.’
This research was funded by the Canadian Institutes of Health Research, the Brain & Behavior Research Foundation and the Ontario Mental Health Foundation. Centre for Addiction and Mental Health (CAMH)

A professor from Case Western Reserve University School of Medicine is one of the lead authors of a study identifying seven new regions of the human genome that are associated with increased risk of age-related macular degeneration (AMD), a leading cause of blindness among older adults.

The AMD Gene Consortium, a network of international investigators representing 18 research groups, also confirmed the existence of 12 other regions—called loci—that had been identified in previous studies..

‘This work represents a big step forward toward solving why some people get AMD, while others do not,’ said Sudha Iyengar, professor of epidemiology and biostatistics at Case Western Reserve School of Medicine and a member of the consortium’s senior executive committee. ‘This disease is not caused by a single change in the DNA, but represents many events that accumulate over the lifetime of a patient. Identification of these genes provides molecular windows into the AMD disease process.’

AMD affects the macula, a region of the retina responsible for central vision. The retina is the layer of light-sensitive tissue in the back of the eye that houses rod and cone photoreceptor cells. Compared with the rest of the retina, the macula is especially dense with cone photoreceptors; humans rely on the macula for tasks that require sharp vision, such as reading, driving, and recognising faces. As AMD progresses, such tasks become more difficult and eventually impossible. Some kinds of AMD are treatable, but no cure exists

Since the 2005 discovery that certain variations in the gene for complement factor H—a component of the immune system—are associated with major risk for AMD, research groups around the world have conducted genome-wide association studies to identify other loci that affect AMD risk. These studies were made possible by tools developed through the Human Genome Project, which mapped human genes, and related projects, such as the International HapMap Project, which identified common patterns of genetic variation within the human genome.

The consortium’s analysis included data from more than 17,100 people with the most advanced and severe forms of AMD, which were compared to data from more than 60,000 people without AMD. The 19 loci that were found to be associated with AMD implicate a variety of biological functions, including regulation of the immune system, maintenance of cellular structure, growth and permeability of blood vessels, lipid metabolism, and atherosclerosis.

As with other common diseases, such as Type 2 diabetes, an individual person’s risk for getting AMD is likely determined not by one but many genes. Further comprehensive DNA analysis of the areas around the 19 loci identified by the AMD Gene Consortium could turn up undiscovered rare genetic variants with a disproportionately large effect on AMD risk. Discovery of such genes could greatly advance scientists’ understanding of AMD pathogenesis and their quest for more effective treatments.

‘This compelling analysis by the AMD Gene Consortium demonstrates the enormous value of effective collaboration,’ said NEI director Paul A. Sieving, MD, PhD. ‘Combining data from multiple studies, this international effort provides insight into the molecular basis of AMD, which will help researchers search for causes of the disease and will inform future development of new diagnostic and treatment strategies.’ Case Western Reserve University

​Can the length of strands of DNA in patients with heart disease predict their life expectancy?
Researchers from the Intermountain Heart Institute at Intermountain Medical Center in Salt Lake City, who studied the DNA of more that 3,500 patients with heart disease, say yes it can.
In the new study, the researchers were able to predict survival rates among patients with heart disease based on the length of strands of DNA found on the ends of chromosomes known as telomeres—the longer the patient’s telomeres, the greater the chance of living a longer life.
Previous research has shown that telomere length can be used as a measure of age, but these expanded findings suggest that telomere length may also predict the life expectancy of patients with heart disease.

Telomeres protect the ends of chromosome from becoming damaged. As people get older, their telomeres get shorter until the cell is no longer able to divide. Shortened telomeres are associated with age-related diseases such as heart disease or cancer, as well as exposure to oxidative damage from stress, smoking, air pollution, or conditions that accelerate biologic ageing.

‘Chromosomes by their nature get shorter as we get older,’ said John Carlquist, PhD, director of the Intermountain Heart Institute Genetics Lab. ‘Once they become too short, they no longer function properly, signalling the end of life for the cell. And when cells reach this stage, the patient’s risk for age-associated diseases increases dramatically.’

Dr. Carlquist and his colleagues from the Intermountain Heart Institute at Intermountain Medical Center tested the DNA samples from more than 3,500 heart attack and stroke patients.

‘Our research shows that if we statistically adjust for age, patients with longer telomeres live longer, suggesting that telomere length is more than just a measure of age, but may also indicate the probability for survival. Longer telomere length directly correlate with the likelihood for a longer life—even for patients with heart disease,’ said Dr. Carlquist. Intermountain Medical Center Heart Institute

Tiny biomolecular chambers called nanopores that can be selectively heated may help doctors diagnose disease more effectively if recent research by a team at the National Institute of Standards and Technology (NIST), Wheaton College, and Virginia Commonwealth University (VCU) proves effective. Though the findings may be years away from application in the clinic, they may one day improve doctors’ ability to search the bloodstream quickly for indicators of disease—a longstanding goal of medical research.
The team has pioneered work on the use of nanopores—tiny chambers that mimic the ion channels in the membranes of cells—for the detection and identification of a wide range of molecules, including DNA. Ion channels are the gateways by which the cell admits and expels materials like proteins, ions and nucleic acids. The typical ion channel is so small that only one molecule can fit inside at a time.
Previously, team members inserted a nanopore into an artificial cell membrane, which they placed between two electrodes. With this set-up, they could drive individual molecules into the nanopore and trap them there for a few milliseconds, enough to explore some of their physical characteristics.
‘A single molecule creates a marked change in current that flows through the pore, which allows us to measure the molecule’s mass and electrical charge with high accuracy,’ says Joseph Reiner, a physicist at VCU who previously worked at NIST. ‘This enables discrimination between different molecules at high resolution. But for real-world medical work, doctors and clinicians will need even more advanced measurement capability.’
A goal of the team’s work is to differentiate among not just several types of molecules, but among the many thousands of different proteins and other biomarkers in our bloodstream. For example, changes in protein levels can indicate the onset of disease, but with so many similar molecules in the mix, it is important not to mistake one for another. So the team expanded their measurement capability by attaching gold nanoparticles to engineered nanopores, ‘which provides another means to discriminate between various molecular species via temperature control,’ Reiner says.
The team attached gold nanoparticles to the nanopore via tethers made from complementary DNA strands. Gold’s ability to absorb light and quickly convert its energy to heat that conducts into the adjacent solution allows the team to alter the temperature of the nanopore with a laser at will, dynamically changing the way individual molecules interact with it.
‘Historically, sudden temperature changes were used to determine the rates of chemical reactions that were previously inaccessible to measurement,’ says NIST biophysicist John Kasianowicz. ‘The ability to rapidly change temperatures in volumes commensurate with the size of single molecules will permit the separation of subtly different species. This will not only aid the detection and identification of biomarkers, it will also help develop a deeper understanding of thermodynamic and kinetic processes in single molecules.’ EurekAlert

Some diseases are caused by single gene mutations. Current techniques for identifying the disease-causing gene in a patient produce hundreds of potential gene candidates, making it difficult for scientists to pinpoint the single causative gene. Now, a team of researchers led by Rockefeller University scientists have created a map of gene ‘shortcuts’ to simplify the hunt for disease-causing genes.

The investigation, spearheaded by Yuval Itan, a postdoctoral fellow in the St. Giles Laboratory of Human Genetics of Infectious Diseases, has led to the creation of what he calls the human gene connectome, the full set of distances, routes (the genes on the way) and degrees of separation between any two human genes. Itan, a computational biologist, says the computer program he developed to generate the connectome uses the same principles that GPS navigation devices use to plan a trip between two locations. The research is reported in the online early edition of the journal Proceedings of the National Academy of Sciences.
‘High throughput genome sequencing technologies generate a plethora of data, which can take months to search through,’ says Itan. ‘We believe the human gene connectome will provide a shortcut in the search for disease-causing mutations in monogenic diseases.’

Itan and his colleagues, including researchers from the Necker Hospital for Sick Children and the Pasteur Institute in Paris and Ben-Gurion University in Israel, designed applications for the use of the human gene connectome. They began with a gene called TLR3, which is important for resistance to herpes simplex encephalitis, a life-threatening infection from the herpes virus that can cause significant brain damage in genetically susceptible children. Researchers in the St. Giles lab, headed by Jean-Laurent Casanova, previously showed that children with HSE have mutations in TLR3 or in genes that are closely functionally related to TLR3. In other words, these genes are located at a short biological distance from TLR3. As a result, novel herpes simplex encephalitis-causing genes are also expected to have a short biological distance from TLR3.

To test how well the human gene connectome could predict a disease-causing gene, the researchers sequenced exomes – all DNA of the genome that is coding for proteins – of two patients recently shown to carry mutations of a separate gene, TBK1.

‘Each patient’s exome contained hundreds of genes with potentially morbid mutations,’ says Itan. ‘The challenge was to detect the single disease-causing gene.’ After sorting the genes by their predicted biological proximity to TLR3, Itan and his colleagues found TBK1 at the top of the list of genes in both patients. The researchers also used the TLR3 connectome – the set of all human genes sorted by their predicted distance from TLR3 – to successfully predict two other genes, EFGR and SRC, as part of the TLR3 pathway before they were experimentally validated, and applied other gene connectomes to detect Ehlers-Danlos syndrome and sensorineural hearing loss disease causing genes.

‘The human gene connectome is, to the best of our knowledge, the only currently available prediction of the specific route and distance between any two human genes of interest, making it ideal to solve the needle in the haystack problem of detecting the single disease causing gene in a large set of potentially fatal genes,’ says Itan. ‘This can now be performed by prioritising any number of genes by their biological distance from genes that are already known to cause the disease. Rockefeller University