For years, researchers have searched for the cause of autism. In recent years, with the development of technology, the claim that autism is a genetic factor has been established
The autistic syndrome has been known to the medical world for nearly seventy years. In 1943, Leo Kenner first described it as a syndrome that demonstrates deficits in language, non-verbal communication and mental and behavioral flexibility. Over the years, additional and different characteristics were discovered among the patients and today they refer to the autistic spectrum, which includes different levels of those deficits.
For years, researchers have searched for the cause of autism. In recent years, with the development of technology, the claim that autism is a genetic factor has been established. First they checked the incidence of the disease in twins. This study showed that if autism was discovered in one twin, there is a 90% probability that the other twin will also develop the syndrome. Later, families were studied in which many cases of autism were seen and several genes were linked to the disease. Although the genetic basis for autism is well established, it does not appear to be simply inherited like other diseases. Since those with autism (forgive me people at the end of the spectrum) rarely produce offspring, the likelihood that the mutations will become established in the population is very low. Thus, even after this partial success, the mystery of the origin of autism remains since most autism patients are single cases in their families. On June 8, 2011, three articles were published in Neuron magazine that examined the genetics of those individual cases.
The researchers tested DNA samples from a thousand families with healthy parents, an autistic child and healthy siblings. These samples allowed the researchers to look for unique changes in the genome of the sick individual. The study examined changes in a genomic factor called CMV (copy number variations). There are regions in the genome where the sequence of letters is repeated a variable number of times. A higher or lower than normal number of repeats may cause a disruption in the level of gene expression. Although different autistic children showed a slightly different number of repeats, the trend was similar: new CMVs (deletions or insertions not present in either parent) are more common in affected children than in their healthy siblings. One study showed a frequency 3.4 times higher in autistic children compared to their siblings, while another study showed a frequency 3.9 times higher. That is, there were much more changes in the amount of genes in the autistic children. The observed changes are rare and some are unique to the individual who presented them. In light of these findings, the authors of the article believe that there are hundreds of potential sites in the genome that can be linked to autism.
Finding the genetic factors is done in stages. The most direct method would be to sequence the complete genomes of autistic children and compare them to their healthy parents and siblings, but this approach is expensive and wasteful. There are more general methods that are the first steps to finding a gene that affects a particular trait. First you find the general area on a certain chromosome and then slowly you find the exact place. It's kind of like finding a book in the library. First you find the closet, then the shelf, then the author you want and finally you find the book.
The new mutations led the researchers to areas already known from previous autism research, but they occurred in mostly new sites. For example, one of the rare mutations that appeared in some of the autistic children in the study was extra copies of 7q11.23 (code for the location of a region or gene on a chromosome, in this case the long arm of chromosome 7). Deletion of this area has been linked to Williams-Bjorn syndrome (WBS), a disease that makes people especially sociable and empathetic. This region is estimated to contain about 25 genes related to social behavior. But even mutations in the same region did not necessarily translate to similar levels of IQ or developmental ability in different patients. Hence factors other than changes at this site in the genome also play a role in autism.
Although the mutations are rare, patterns of disrupted intracellular signaling pathways and networks could be found in them. One of the studies looked at what the genes found do. This information is available online if you know what you are looking for. The genes in which the mutations were found are involved in the formation of synapses (the transition between nerve cells), the internal structure of the nerve cells and the formation of the axon (transmits the nerve message to the synapse) and the dendrites (receive the nerve message from the synapse). In other words, the findings strengthen the argument that the phase that goes wrong in autism is the wiring of the brain, the phase of creating connections between nerve cells, and not, for example, the phase of creating nerve cells or how they function.
At the protein level, hundreds of proteins that are produced incorrectly, too often or not at all, involved in autism have already been identified. Understanding the signaling pathways of the proteins may lead to medical intervention possibilities if you find a way to balance a disturbed pathway. But it sounds easier than it really is, in reality it is an equation with hundreds of variables.
The study offers an explanation why autism is 4 times more common in boys than in girls. It seems that girls are more resistant to the development of the signs of autism - a greater genetic disorder is needed to cause autism in girls than in boys. It may be because the social side of girls is more developed. This finding suggests the possibility that women will become carriers of problematic mutations, but the analysis performed in the study showed an equal chance of passing the mutation between fathers and mothers.
Although the new studies find a genetic explanation for a large part of the autism cases, an influence of the environment cannot be dismissed. The environment can affect both the level of expression of various genes, directly or through epigenetics, but also the rate of mutations itself. Many environmental factors can promote damage to the genome (carcinogenic substances for example), and these damages may lead to the creation of the new mutations discovered in these studies.
To this day, the attempt to find an environmental factor related to autism, has resulted in the rejection of more factors (vaccines for example) than their approval. A recently published study suggests a connection to taking vitamins intended for pregnant women in the months before becoming pregnant and in the first month of pregnancy. These vitamins contain factors such as vitamin B and folic acid which are essential for the development of the nervous system and the children of the women who took those vitamins were at a lower risk of developing autism.
Currently, the treatment of autism is based on behavior or accidental discoveries. Although the genetic discovery cannot yet help with the treatment itself, it can allow a review of the population to identify autism before it develops and an early start of behavioral therapy may improve the child's level of functioning.
The articles:
Neuron, 2011. DOI: 10.1016/j.neuron.2011.05.015, 10.1016/j.neuron.2011.05.002, 10.1016/j.neuron.2011.05.021
11 תגובות
As far as I know, sequencing a person's genome costs about $100. That doesn't sound like a lot of money to me in terms of a biological experiment.
Hi, the CNV is a name for a specific chromosome or a name for changes in which there is a repetition of sequences? In addition, are they born with the disruption in sequence and are they in coded areas. Thanks:)
Israel
I read the "research" in question and it is extremely bad:
First of all, it is not a scientific study at all, its authors are not scientists and it was not published in any scientific journal. In terms of conflicts of interest, two of the authors are lawyers who deal with vaccine damage claims and all of them have connections with anti-vaccination organizations.
And for the "research" itself:
1. Trying to present the decisions of a compensation court as if it were scientific proof is wrong. The level of proof required to obtain compensation in court is much lower than that required for scientific proof. In order to win compensation at trial all that is required is for the judge (who is not a scientist) to think that there is a 50 percent or greater chance that the vaccine in some way caused the plaintiff's problems. On the other hand, in science this way will have to go through a series of tests and tests before it is accepted as proven by science. That is why court rulings do not disprove science.
2. Contrary to the claims, in none of the cases (perhaps except for one case where the information is unclear) was it not established that the vaccine caused autism. All they found was that among the children who received compensation there were some with autism which was to be expected anyway since autistic children are also vaccinated.
3. Of the 83 children, most were not diagnosed with autism at all, but the researchers inflated the numbers by considering children who suffer from problems that have symptoms that are also common to autism as autistic.
In fact, in a large part of the article, they perform logical flip-flops to try to explain how it is that children who do not have autism and did not receive compensation for autism actually do have autism and were compensated for it.
4. The authors, on the other hand, tried to reduce the importance of the fact that the court rejected thousands of cases of claims of a connection between autism and vaccines and also determined that the main ideas that were proposed to explain this connection (mercury in vaccines, Wakefield's proposal) are not reasonable.
5. Throughout the article, they distort the state of knowledge regarding the connection between vaccines and autism by giving excessive emphasis to the claims of the opponents of vaccines.
6. The great majority of the judgments given were given until the mid-90s, that is, before the idea of the connection between vaccines and autism began to gain popularity and before the main studies in the field were carried out. So it is not clear how these judgments contradict the scientific knowledge that was created after they were given.
And that's just the tip of the iceberg. In short, this is a very poor "research" that mainly shows how desperate the opponents of vaccines are that the science does not support them.
The magic number 90%, a number often quoted by members of the skeptic cult, is similar to the ethics of networks
Marketing that advertises a 90% discount in large and "up to" in small.
There have been some twin studies limited in scope with numbers ranging from 60% to 90% concordance between identical twins.
But on July 4th of this year (yes while most people in the US are busy with Independence Day matters) a study was published
Twins, the most extensive in scope to date (192 pairs of twins compared to dozens of singles in the previous studies):
Genetic Heritability and Shared Environmental Factors Among Twin Pairs With Autism.
http://www.ncbi.nlm.nih.gov/pubmed/21727249
CONCLUSION:
Susceptibility to ASD has moderate genetic heritability and a substantial shared twin environmental component.
In addition, in the recent CNV studies, most of the cases were de-novo - new mutations, this can also indicate high parental age, but also environmental factors that affect the stability of the genetic material.
The weight given to genetics will probably decrease again if a study is carried out in identical twins that takes into account cases of shared and separated placentas like the one conducted on identical twins and schizophrenia, which probably has a common etiology with some of the autism cases:
Prenatal development of monozygotic twins and concordance for schizophrenia
http://www.ncbi.nlm.nih.gov/pubmed/7481567
Another new study shows that the chance of another case in the family is 2-3 times higher than previously thought
Recurrence Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study
http://pediatrics.aappublications.org/content/early/2011/08/11/peds.2010-2825
Autism in most cases involves inflammation (search words il-6 TNF-alpa NF-kappa-B "microglia activation), which can start in the womb and be exacerbated by environmental factors...
The article is indeed interesting, especially to everyone who is close to the subject - like me - but it does not innovate anything.
In conclusion, the article raises the bar of expectations for some innovation in the field, but the results of the research show that no discovery was found. Readers' knowledge does not increase.
In the same way, the topic of the article could have been "about a nearby black hole" and to point out that a long and comprehensive research done by such and such did not discover any such black hole.
Israel:
You should know that it is possible to establish the existence of a genetic basis without knowing the genes that share it.
All that is needed, for this, is to show that autism has a connection to any genes - even if these are unknown.
The idea is well demonstrated in the twin tests described in the article.
This is what the author was talking about when she said that "the genetic basis for autism is well established"
The article also has no direct connection to the question of vaccinations because even if someone believes in this conspiracy, he must refer to the heredity tests and change his claim to something like this: "The tendency to develop autism as a result of receiving the vaccine is genetic."
Of course, on the topic of the vaccine conspiracy, if I have to choose between the opinion of the majority of scientists specializing in the subject and your opinion, I choose the opinion of the scientists, but what I wanted to emphasize is that the current research does not help to decide the vaccine controversy and neither side in that controversy should use it.
h first
How is this an excuse that was refuted, when 83 families received compensation from the administration quietly in US courts,
Due to the vaccine damage that caused their children autism?
Read the peer-reviewed study that revealed it
http://digitalcommons.pace.edu/pelr/vol28/iss2/6/
Israel, there are many genetic markers that we still do not understand when and how they are expressed.
The thing with the vaccines is an excuse that has been refuted.
Believe what you want, but the word "vaccines" can be replaced by "malnutrition" or a thousand other reasons.
This is not proof of anything, even if it is tempting to believe that vaccines are harmful.
The example of the Somali children is a classic example to see what causes autism:
Dr. Peter Fletcher, former Chief Scientist at the British Ministry of Health:
"I have always thought since I first heard about the Somali children that this really proves the causal role of vaccines. The Amish children who have no vaccines have no autistic-like disorders and the Somali children who are newly exposed to aggressive vaccine programs have exceptionally high levels!
What more evidence is needed?"
http://www.huffingtonpost.com/david-kirby/former-uk-science-chief_b_146717.html
"Although the genetic basis for autism is well established"
This is clearly not true
Taken together, these genetic changes could explain up to 20% of cases of autism
But much about autism remains a mystery, including the cause of the other 80% of cases
http://www.usatoday.com/news/health/2010-06-10-autism10_st_N.htm
Another interesting article in genetics!
I noticed that the author brings quality articles on the subject, please continue 🙂
It is clear that autism is indeed a broad spectrum, but the progress is impressive