Genetics

Genetics play a bigger role than environmental causes for autism

Genetics plays more of a role in the development of autism than environmental causes, according to new research published Sunday in Nature Genetics.

The study found that 52% of autism risk comes from common genes, while only 2.6% are attributed to spontaneous mutations caused by, among other things, environmental factors.

Genetics play a bigger role than environmental causes for autism

“These genetic variations are common enough that most people are likely to have some,” said Joseph Buxbaum, a researcher at the Mount Sinai School of Medicine and one of the lead authors on the study. “Each one has a tiny effect on autism risk, and many hundreds or thousands together make a significant risk.”

Using Sweden’s health registry, the researchers compared 3,000 people with autism to 3,000 people without autism to determine the degrees that common and rare genes, as well as spontaneous mutations, contribute to autism risk. The study authors also compared the study’s results with a parallel study of 1.6 million Swedish families that identified specific genetic risk factors.

Buxbaum says the presence of these common genes can only determine the risk of autism, not whether or not the condition will develop. And even though spontaneous mutations only account for a small percentage of autism risk, their effect is significant. “[Individuals] might have all the common variants there as part of their background risk, but it took this initial hit to push them over the edge,” Buxbaum said.

Chris Gunter, an autism researcher at the Marcus Autism Center and professor at the Emory University School of Medicine, says the findings of this study are similar to those reported in other studies.

“There is no one gene for autism,” Gunter said. “Instead there are many different genetic variations which each contribute a little bit to the risk of developing the group of symptoms we diagnose as autism.” She added that we still don’t know exactly how much these different factors contribute to the development of autism.

Once scientists accumulate more data on the autism population, Buxbaum says this new research could help develop a “risk score” – such as the one that exists for heart attacks – that would help patients determine the likelihood of family members developing autism.  “The autism field has changed dramatically,” Buxbaum said. “We now have immense power to find both common and rare and spontaneous mutations in autism. That’s really the exciting part.”

Source: cnn

Gene Study Offers Clues to Why Autism Strikes More Males

why girls are less likely than boys to have an autism spectrum disorder.

It turns out that girls tend not to develop autism when only mild genetic abnormalities exist, the researchers said. But when they are diagnosed with the disorder, they are more likely to have more extreme genetic mutations than boys who show the same symptoms.

“Girls tolerate neurodevelopmental mutations more than boys do. This is really what the study shows,” said study author Sebastien Jacquemont, an assistant professor of genetic medicine at the University Hospital of Lausanne, in Switzerland.

“To push a girl over the threshold for autism or any of these neurodevelopmental disorders, it takes more of these mutations,” Jacquemont added. “It’s about resilience to genetic insult.”

The dilemma is that the researchers don’t really know why this is so. “It’s more of an observation at a molecular level,” Jacquemont noted.

In the study, the Swiss researchers collaborated with scientists from the University of Washington School of Medicine to analyze about 16,000 DNA samples and sequencing data sets from people with neurodevelopmental disorders, including autism spectrum disorders.

The investigators also analyzed genetic data from almost 800 families affected by autism for the study, which was released online Feb. 27 in the American Journal of Human Genetics.

The researchers analyzed copy-number variants (CNVs), which are individual variations in the number of copies of a particular gene. They also looked at single-nucleotide variants (SNVs), which are DNA sequence variations affecting a single nucleotide. Nucleotides are the basic building blocks of DNA.

The study found that females diagnosed with any neurodevelopmental disorder, including attention-deficit/hyperactivity disorder and intellectual disability, had more harmful CNVs than males who were diagnosed with the same disorder. Females with autism also had more harmful SNVs than males with the condition.

“There’s a well-known disparity when it comes to developmental disorders between boys and girls, and it’s been puzzling,” Jacquemont said. “And there have been quite a bit of papers trying to investigate this bias that we’ve seen in the clinic.”

The study authors pointed out that autism affects four boys for every one girl. The ratio increases to seven-to-one when looking at high-functioning autism cases.

It’s an interesting study, said Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at the Steven & Alexandra Cohen Children’s Medical Center of New York.

“It’s not an easy study to read, but certainly the take-away suggests it tries to lend further support to the assumption that the ratio of males to females [who have autism] is affected by genetic vulnerabilities — that it has a genetic underpinning,” Adesman said.

What do the findings mean for parents and patients?

Adesman said there are no immediate benefits, but the knowledge can help direct future research.

“This isn’t going to lead to a breakthrough in treatment, but from a clinical standpoint it may help researchers and academics understand why it is that developmental disorders seem to be more common in boys than girls,” he noted.

The new research also reinforces that genetic differences — or vulnerabilities — aren’t limited to sex chromosomes, Adesman added.

“The presumption has been, ‘Well gee, boys have a Y chromosome and girls don’t, so are there problems with the Y chromosome that explain it?'” Adesman noted.

“The bottom line is that there are a lot of different genetic abnormalities and atypicalities that result in developmental disorders in children and adults,” Adesman explained. “Women seem to be a little more resilient in terms of being able to have minor abnormalities without having a developmental problem.”

Source: health

33 new genes behind onset of cancer uncovered

A research team has found many new cancer genes – expanding the list of known genes tied to these cancers by 25 percent.

Moreover, the study shows that many key cancer genes still remain to be discovered. The Broad Institute-led research team’s work, which lays a critical foundation for future cancer drug development, also shows that creating a comprehensive catalog of cancer genes for scores of cancer types is feasible with as few as 100,000 patient samples.

Broad Institute founding director Eric Lander, senior co-author, said that the knowledge of genes and their pathways will highlight new, potential drug targets and help lead the way to effective combination therapy.

Over the past 30 years, scientists had found evidence for about 135 genes that play causal roles in one or more of the 21 tumor types analyzed in the study. The new report not only confirms these genes, but, in one fell swoop, increases the catalog of cancer genes by one-quarter.

It uncovers 33 genes with biological roles in cell death, cell growth, genome stability, immune evasion, as well as other processes.

The result has been published in the journal Nature.

Source: Zee news

Smoking during pregnancy could make your baby gay

Smoking and drinking during pregnancy could make your baby gay and stupid, if the claims of a neuroscientist are to be believed.

A controversial study has found that a pregnant woman’s lifestyle could influence their child’s IQ or sexuality.

Dr Dick Swaab – professor of neurobiology at Amsterdam University – claims that drinking, taking drugs or living in a area with high pollution levels have an impact on the development of foetuses and could affect children later in life.

Taking synthetic hormones and smoking while pregnant can increase the chances of girls becoming lesbian or bisexual, while drinking and drug-taking could lower a child’s IQ, Dr Swaab suggests.

And the more older brothers a boy has, the more it is thought to increase his chance of being gay, it is reported. The study claims this could be because the mother’s immune system develops stronger responses to male hormones with each son that is born.

Dr Swaab also believes living in an area of high pollution is linked with an increased risk of autism.

He told the Sunday Times: ‘Pre-birth exposure to both nicotine and amphetamines increases the chance of lesbian daughters.

‘Pregnant women suffering from stress are also more likely to have homosexual children of both genders because their raised level of the stress hormone cortisol affects the production of foetal sex hormones.’

He added: ‘In women who drink a lot, cells that were meant to migrate across the foetal brain can end up leaving the brain altogether.’

However, Dr Swaab recognised lifestyle factors were a small influence and added that genetics play the most important role in child development.

Source: Metro News

New method could help in early detection of colon cancer

Bettina Scholtka, said that tumour cells are released into stool from the surface of precancers and early-stage colon cancers

Scientists have found a new method to detect genetic variations that initiate colon cancer could be readily used for non-invasive colon cancer screening.

Bettina Scholtka, Ph.D., assistant professor in the Department of Nutritional Toxicology at the University of Potsdam in Nuthetal, Germany, said that tumour cells are released into stool from the surface of precancers and early-stage colon cancers, but detecting a cancer-initiating genetic mutation among a large quantity of normal DNA from a patient’s stool is like looking for a needle in a haystack.

Scholtka said that by combining for the first time locked nucleic acid-based, wild-type blocking polymerase chain reaction and high-resolution melting, we were able to achieve the desired sensitivity.

Scholtka and colleagues used 80 human colon tissue samples representing cancers and precancers to detect genetic variations using a combination of two techniques: The first technique — locked nucleic acid (LNA)-based, wild-type blocking (WTB) polymerase chain reaction — suppressed normal DNA present in large quantities in the sample; and the second technique — high-resolution melting (HRM) — enhanced the detection of genetic variations.

The researchers were able to detect APC variations in 41 of the 80 samples. They were also able to detect previously unknown variations in APC. In contrast, the routinely used technique called direct sequencing could detect variations only in 28 samples.

They then analyzed 22 stool samples from patients whose colon tissues had APC variations, and nine stool samples from patients whose colon tissues did not have APC variations, as controls. They were able to detect APC variations in 21 out of 22 samples.

The study has been published in Cancer Prevention Research.

Genetic cause of childhood leukemia revealed

Scientists have uncovered a genetic link specific to the risk of childhood leukaemia.

Study author Kenneth Offit, MD, MPH, Chief of the Clinical Genetics Service at Memorial Sloan-Kettering Cancer Center, said that at the very least the discovery gives us a new window into inherited causes of childhood leukemia.

Offit said that more immediately, testing for this mutation may allow affected families to prevent leukemia in future generations.

The mutation was first observed in a family treated at Memorial Sloan-Kettering of which several family members of different generations had been diagnosed with childhood acute lymphoblastic leukemia (ALL).

A second, non-related, leukemia-prone family cared for at a different hospital was later found to have the same mutation. A series of experiments were conducted confirming that the observed mutation compromised the normal function of the gene, which may increase the risk of developing ALL.

The inherited genetic mutation is located in a gene called PAX5, which is known to play a role in the development of some B cell cancers, including ALL.

The findings have been published in the journal Nature Genetics.