Schizophrenia, autism and genetics

Scientists have found the birthplace of schizophrenia
Alexey Timoshenko, GZT.RUScientists have found a rare mutation that increases the risk of developing schizophrenia.

By comparing the genes of several thousand healthy people with patients, researchers were able to detect "extra" genes that can lead to the development of schizophrenia.

Psychiatrists and geneticists from the UK, USA and Finland conducted an extensive study, which involved more than sixty specialists and slightly less than 11 thousand both healthy and schizophrenic people. Scientists, whose results are presented in the journal Nature Genetics, have found that doubling one small section in the 16th chromosome can increase the risk of developing schizophrenia by eight times.

Schizophrenia and chromosomes

Schizophrenia, as psychiatrists and neuroscientists recognize, remains one of the most difficult diseases. Diagnostic manuals list several dozen conditions that somehow fall into the general category of "schizophrenia". Disorders of consciousness and speech, hallucinations, delirium, apathy, sudden mood changes – many of these symptoms can be characteristic of other disorders, so even making a diagnosis is far from an easy task.

Tomograms of the brain of a schizophrenic patient (left) and a healthy person.
The colors indicate the activity level – the maximum is encoded in red.

And understanding why the brain begins to function in such a strange and unusual mode is even more difficult. Scientists have not yet been able to unambiguously list all the reasons that can provoke the development of the disease – for example, not everything is clear with the heredity and genetics of schizophrenia.

For example, it is known that if one of the identical twins is sick with schizophrenia, then the chances of the second one getting sick with this disease are very high, but not equal to 100%. People whose genes are exactly the same (identical twins develop from the same egg) get something by inheritance, but here's what?

The analysis conducted by an international group of researchers, apparently, will partially solve the mystery of one of the darkest diseases. The DNA of sick people, as scientists have been able to demonstrate, often contains "extra" genes.

Thanks, no more supplements

This is not the first mental illness that is caused by excess genetic material. Three copies of the 21st chromosome instead of two, for example, lead to the development of a severe congenital disease, trisomy 21. This disorder, which leads, among other things, to loss of intelligence, is known to most people by the name of the English doctor George Down – Down syndrome, along with idiocy, cretinism and imbecility, is known not only to doctors.

However, in the case of schizophrenia, the genetic differences were not so striking. Instead of repeating the entire chromosome as a whole (recall that DNA is distributed between 23 chromosomes and each cell carries two sets), we are talking about repeating a small section with the code designation 16p11.2. Judging by its length, there may not be many genes there, and now the task of scientists is to find out what exactly 16p11.2 is responsible for.

Autism or schizophrenia?

It should be noted that some assumptions about the role of 16p11.2 have already been put forward. In particular, the researchers draw attention to the fact that medical genetics has already encountered this site. However, then it was not about schizophrenia, but about autism, and not about repetition, but about the removal of this fragment.

Shane McCarthy, one of the participants in the study, says that the 16p11.2 site may carry some genes important for brain development, and both an excess and a lack of these genes adversely affects the developing brain. If we take into account the fact that a gene has recently been found, the level of activity of which directly determined the structure of the cerebral cortex, then this assumption looks quite plausible.

And an excess of genes in some cases is no better than their lack. Scientists do not yet have answers to the questions, the violation of which genes, how exactly and at what point lead to an increase in the risk of schizophrenia. However, researchers now know where to look for answers to their questions – along with 16p11.2, scientists have indicated three more suspicious sections of the chromosome.

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27.10.2009