The most severe form of schizophrenia – chronic schizophrenia – is hereditary. Descendants in the male line can have genetic disposition to this disease. Russian scientists from the Centre of Mental Health of Russian Academy of Medical Sciences found out the genotype, which was common for men, suffering from a chronic form of schizophrenia. Results of this study can become the basis for development of a test system for early diagnostics of schizophrenia, which is especially important in case of such a terrible disease.

Latest studies showed that a certain protein called “brain-derived neurotrophic factor” (BDNF) can be related to pathophysiologic mechanisms of schizophrenia. Brain-derived neurotrophic factor regulates growth, differentiation and development processes of neurons. Moreover, BDNF is involved into processes, linked with brain’s synaptic flexibility. Researchers showed that replacing only one amino acid valine, located at certain position on protein’s molecule, with methionine was enough to disturb cellular distribution of the protein. The result is low concentration of mature protein in respective parts of brain, and as a consequence neurons of frontal cortex stop functioning properly, which leads to schizophrenia development.

 

 

How does “wrong” protein form? A gene, responsible for BDNF synthesis, is located on the 11^th chromosome and exists in two forms or alleles – valine variant and methionine variant. Every human being has two copies of the mentioned gene, since we get one chromosome from our mother, and another – from our father. Knowing this, scientists supposed that three variants of gene combination could exist: first is when people have valine in both copies of BDNF-coding gene (Val/Val); second is having two methionines (Met/Met) in this gene; and the third is when people receive one valine and one methionine (Val/Met) copy of the gene.

Fellows of the laboratory of clinical genetics (the Centre of Mental Health of Russian Academy of Medical Sciences) were the first to perform a massive study of allele frequencies for BDNF-coding gene on Moscow dwellers. The study involved 783 patients with schizophrenia and 633 healthy volunteers. Chronic form of schizophrenia is much more severe than episodic form, during which symptoms disappear from time to time. Experiments revealed that chronic schizophrenia in men was linked with Val/Val allelic variant – male patients with this disease had Val/Val gene type 1.3 times oftener than healthy men did. As for women, all allelic variants occurred with the same frequency despite the fact of being ill or healthy.

Of course, scientists know that schizophrenia is a polymorphous disease, and its development depends on many genes. However, their study allows building a test-system for detection of high-risk group. Early diagnostics provides starting immediate therapy, which is a very important factor for such disease as schizophrenia.

Source: Living Systems

Kizilova Anna