The Genetic of Autism

July 17, 2015

By Medical Discovery News

The Genetics of Autism

In the past decade, autism has garnered a lot of media attention. Lately much of the focus has been on finding the cause. Much is still a mystery, despite confirming that vaccines and parenting are not responsible. Now a new study of twins has given us another clue, revealing that the influence of genetics on the development of autism may be between 56 and 95 percent.

According to the Centers for Disease Control, one in 68 children have autism, a neurodegenerative disorder that exists on a spectrum, meaning its symptoms and their severity varies tremendously. A hallmark feature of autism is impaired social interaction, noticeable even in babies. Those with autism find it difficult to interpret what others are thinking or feeling because they miss the social clues most take for granted. Other symptoms can include repetitive movements such as spinning or rocking, speech delays, and self-destructive behaviors. Children with autism can also have a variety of other conditions including epilepsy, Tourette’s syndrome, learning disabilities, and attention deficit disorder (ADD).

The cause of autism is probably rooted in genetics and environment. Comparing sets of twins is a well-established way of clarifying the extent of both these influences. Scientists in London studied over 6,400 pairs of twins in England and Wales between 1994 and 1996, all raised by their parents in the same environments. The data they collected revealed that the chance of identical twins having autism was 77-99 percent, whereas the chance of non-identical twins having autism was 22-65 percent. This suggests that additive genetic factors contribute to 56-95 percent of autism cases. This is far higher than previous estimates, which assumed environmental influences were more of a factor.

While no one gene has been attributed to autism, the majority of the genes that are associated seem to be linked to one specific symptom. For example, the gene EN2 is often studied for its role in autism because it is critical to midbrain and cerebellum development. Reelin, a protein found mainly in the brain, also plays an important role in autism development. In adults, reelin is important to learning and memory and is critical to inducing and maintaining long-term neuronal connections. Autistic individuals consistently show elevated levels of serotonin, otherwise known as the feel-good hormone. This has led researchers to examine the role of genes involved in serotonin regulation as potential causes of autism. Another hormone system called arginine-vasopressin affects social behavior, so one of the genes that regulates it is a candidate for autism as well. These are just a few of the many genes being studied.

As more people become aware of autism and more children are diagnosed, the pressure is building to further understand this disorder. Discovering the causes might translate to better diagnostics and treatment for autism.

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Vaginal or C-section: Does it matter?

Feb. 20, 2015

An infant

In the climax of William Shakespeare’s “Macbeth,” the title character is sword fighting and believes himself invincible because he was given a prophesy that said “no man born of woman shall harm thee.” Yet, that is how he was tricked, for his rival, Macduff, was “from his mother’s womb untimely ripped.” This and other historical references show that cesarean sections have been used for centuries, but today the high success rate has made them more common than ever.

The origin of the term Cesarean is popularly and probably falsely attributed to the birth of Julius Caesar. This is unlikely, since C-sections at this time almost always resulted in the death of the mother, and historical records mention Caesar’s mother later in his life. However, the origin may still be linked to Caesar as a law enacted during Caesar’s reign stated that a dead or dying pregnant woman was to be cut open and the child removed from her womb to save the child. Widespread use of this procedure began after anesthetics and antimicrobial therapies became available in the 20th century.

In 1965, 4.5 percent of America’s babies were delivered via C-section. Today that figure has risen to almost one in three, and is on the rise worldwide as well. There are plenty of medical and nonmedical reasons for this shift from vaginal childbirth. Both come with side effects and consequences, some lasting longer than others. For example, C-sections have been linked to increased rates of diabetes and obesity, although we’re not sure why. In a recent study, birth by C-section lead to epigenetic changes in the child’s DNA.

Epigenetics are changes in our DNA that don’t result from changes in our genetic code. These changes can come from environmental factors, such as smoking, that alter the ability of a gene to be seen or expressed. What we didn’t understand until relatively recently is that epigenetic changes can be transmitted to offspring. So you are the product of your parents’ DNA and the environmental factors that affected your DNA in your lifetime and their lifetime before you were born. Then your DNA and epigenetic information is passed on to new generations. These changes accrue and could affect your children or grandchildren. So the descendants of a smoker may inherit more than their name, but epigenetic changes in DNA as well.

New research suggests certain epigenetic changes in a baby’s DNA called methylation are different depending on the type of birth. When DNA becomes methylated, it changes whether a gene is used to make a protein and this can then alter the properties of specific cells. In this study, researchers compared the DNA methylation patterns in stem cells of 25 vaginally delivered babies and 18 delivered by C-section. Distinct methylation changes were seen in more than 300 different regions of the genome between the two groups. Interestingly, many of these regions are associated with genes that control the immune system. We don’t know how these epigenetic changes affect the immune system and ability to fight disease, and don’t have sufficient information to link these differences to later health issues. But this remains an intriguing possibility and awaits more research.

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