A word about the genetics of behavior

Anton Chugunov, "Biomolecule"From time immemorial, the study of human behavior has been considered a territory where molecular scientists, geneticists and other adherents of the "mechanistic" view of life have absolutely nothing to do: it's all so complicated, spiritual and generally far from the banal interaction of molecules.

However, gradually such a taboo remains in the past, and many studies are already beginning to snatch out of the darkness of the unknown individual details linking genetics and behavior. This note, based on a small review published in the journal Science, will successfully complement the material "Genes control behavior, and behavior — genes", which appeared on the website "Elements" and is based on articles and reviews published in the same issue of Science.

It's hard to believe that human behavior and other aspects of higher nervous activity can be somehow related to genes. You can often hear in response to a statement about, for example, a sexual (and therefore genetically predetermined) difference in mathematical abilities, an irritated statement like "well, then show me the mathematical gene!". Of course, there is no "mathematical gene", but this does not mean that mathematical abilities (as well as more general abilities to concentrate attention, perceive abstract logical constructions, etc.) are not "encoded" at the DNA level in any way. The fact is that all complex phenomena, one way or another connected with higher nervous activity and not directly caused by some severe hereditary disease, are based on the most complex effects of the interaction of many genes, only creating the possibility of the formation of certain neural structures and personal characteristics, but certainly not determining them 100%. If a person possessed at least a thousand copies of the "mathematical gene" (if it existed), without systematic development of abilities, of course, nothing would work, and dreamers should remember this carefully. It's just that, probably, for many newspaper headlines like "The gene of cruelty has been discovered" or "Divorces are genetically predetermined" can create the impression that both successes and failures of people in all spheres of life can already be explained at the level of genes (but do readers of such newspapers know what genes are?), and, consequently, and it's not worth straining too much.

And what, it would be convenient to explain the poor social adaptation by heredity, and the behavior of everyone pruning and rushing from lane to lane of a "private citizen" by the gene of militancy. Oh, by the way, are Hemingway's famous depressions caused by problems with the dopamine receptor? Or maybe adultery is a direct consequence of the structural features of the vasopressin receptor gene? Studies indicate a certain connection between these phenomena, although it is not necessary, of course, to explain your mistakes and other people's successes solely by this.

Decades of research involving families and relatives, twins and foster children have shown that a certain (and sometimes quite significant!) the relationship between the genotype and predisposition to a certain type of behavior in model situations is present, but that compared to the search for the most complex patterns that determine this relationship, the identification of mutations that cause the development of, for example, Huntington's disease [1] looks like just child's play. It is now quite obvious that the ability to speak fluently and learn languages, responsiveness and willingness to help others, and other mental qualities cannot be determined by any one gene, but are formed under the influence of many factors (of which education is probably the main one so far). In addition, the same gene is likely to be involved in many processes at once — for example, predisposition to depression, overeating and impulsive behavior, making the task of establishing unambiguous connections almost impossible. The study of these factors is undoubtedly the most difficult task ever faced by geneticists, behaviorists and psychologists.

What follows is a small review of the genes that "lit up" in the headlines: what exactly is known about them and how their variability can affect personal qualities.

Likes — does not like...Genetic scanning for the strength of marriage bonds?

What? Isn't it too similar to the slogan of one of the magic salons? Despite the solid shade of yellowness of such a statement, one Canadian firm really offers for $ 99 to analyze the vasopressin 1a receptor gene (AVPR1a), which has become infamous as the gene of cruelty or the gene of divorce, in the couple who applied. However, how can such a test be more informative than the long-established fortune-telling by chamomile?

In addition to regulating water-salt metabolism, the peptide hormone vasopressin has recently been credited with the function of biochemical mediation in the formation of attachment to a sexual partner or offspring. A study on voles — and prairie voles, unlike meadow and mountain voles, are strictly monogamous and faithful to their partners — showed that there are significant differences in the sequence of the vasopressin receptor gene promoter in monogamous and polygamous mice. In prairie voles, this region is several bases longer, which leads to an increase in receptor expression [2]. The endgame of the study devoted to the relationship between the vasopressin receptor and "correct" behavior was the demonstration of the fact that the increased expression of the receptor in the brain of male meadow vole (more precisely, Pennsylvania vole, Microtus pennsylvanicus — VM) makes them, like prairie "colleagues", less "rampant" and more committed to the family hearth and caring for offspring. (You can read more about this in the article "Genes control behavior, and behavior is controlled by genes" [3].)

Genes cannot explain everything, but in Sweden, a study was conducted with the participation of 500 same-sex twins, each (or each) of whom was in a civil or de facto marriage for at least five years [4]. The subject of the study was the relationship of the structure of the promoter of the AVPR1a receptor gene with the results of a questionnaire that included questions like "how often do you kiss your partner" or "how often do your interests and your partner's interests intersect outside the family circle". (This questionnaire was supposed to assess the "temperature" of family relationships.) It turned out that for men whose AVPR1a gene promoter sequence was shorter (and several variants were found), less strong attachment to wives was characteristic than for the rest. These men are less likely to get married, and in marriage they are more likely to suffer a crisis of family relations. So, has the "divorce gene" been found after all? Perhaps you should not hurry: reality may be more complicated than this scheme convenient for revelers.

In the work of a group of Israeli scientists, another effect of variations in the promoter of the vasopressin gene affecting social relations was studied — however, this time not on love and family "decency", but rather on altruism [5]. The measure and scrap of altruism was the "dictator game", often used in research on economics and sociology, which in this case consisted in the fact that a group of 200 volunteers was divided equally into subgroups "A" and "B", giving them different "powers". Each "A-shka" was given $ 14 and offered to share the money at his discretion with the "B-shka", who, according to the rules of the game, was not familiar to him. About 18% did not give anything to the "Be-shkam", 6% gave all the money, and the rest shared part of the money. So it turned out that the "egoists" identified in this game have the same variant of the AVPR1a gene promoter as people who tend to have less strong family relationships (which have already been discussed). Scientists argue that the distribution of vasopressin receptors in the brain characteristic of these people leads to the fact that the act of giving (both material goods and their love or friendship) turns out to be less significant for them on the internal scale of values (which, it turns out, is "regulated" biochemically!). In addition, it has been suggested that the short version of the promoter may be associated with autism, a disease whose main feature is the inability to establish contacts with other people.

However, neither in family life nor in friendship are there such unambiguous connections as in pathophysiological conditions (although ...), and, therefore, it is probably not worth hoping for "genetic fortune-tellers".

I will surviveSome people are called weak-willed because they are not able to resist the circumstances surrounding them, and even a minor incident can upset them, while others steadfastly overcome all adversities and inevitably move towards the intended.

However, it seems that this kind of resistance has not been without genetics: emotional ups and downs are associated with the neurotransmitter serotonin, the transporter of which (SERT) will be discussed further.

In the now classic 1996 paper by Klaus-Peter Lesch, it was revealed that the length of regulatory sequences preceding the SERT gene is also associated with human behavior [6]. In those of the 505 volunteers who were classified according to the questionnaire as susceptible to neuroses (depression, anxiety, etc.), a short regulatory sequence was detected, present in one or two copies, while in more "calm" subjects, a long version of the promoter was found. The "short" form of the promoter causes a more active secretion of serotonin into synapses, which, as has been shown in both animals and humans, causes anxiety and anxiety. However, one should not delude oneself with the idea of absolutely accurately predicting a person's character based on the results of genotyping: according to statistical processing, the short form of the SERT promoter is responsible for only 4% of depressions and negative emotions. However, psychologists note that 4% in the case of personal qualities is already a lot, since scientists have not been able to detect a single gene before, variations in which gave at least such a level of causality.

Another paper, published in 2003, analyzed the relationship between stressful life events and related experiences in a group of 847 people who were surveyed for depression between the ages of 20 and 26. Among the subjects who did not have to experience "blows of fate" during this period (such as the death of loved ones, dismissal from work, personal failures, etc.), there was no significant relationship between the SERT gene and the likelihood of depression (and this probability itself was low). The most interesting thing was in the group of people who had experienced four or more stressful episodes: 43% of carriers of the "short" isoform of the SERT promoter reported a depressive period associated with troubles, while among the owners of the "long" variant, the number of depressions was almost two times lower. In addition, it was found that people with a "short" SERT promoter are more likely to experience depression in adulthood if they experienced abuse in childhood; in the other part of the studied group, such a pattern was not observed.

But even here, of course, it is premature to say something concrete. Many scientists with numbers in their hands prove that for such weak effects, the size of the samples used is clearly insufficient, and the influence of serotonin and its transporter on physiology is so widespread — these are sleep disorders, cardiovascular activity, schizophrenia, autism, and the state of search for thrills - that to judge their effect on behavior is possible only in the most general terms.

The gene of militancyIn 2006, it was discovered that a special form of the monoamine oxidase-A gene responsible for the cleavage of neurotransmitters in the brain may be responsible for the "famous" belligerent behavior of the New Zealand Maori tribe.

According to the New Zealand researcher Rod Lea, 60% of Asians (the anthropological type of Polynesians, including Maori, was formed as a result of the mixing of ancient southern
Mongoloids and negro-Australoids) are carriers of a special, "militant" variant of the MAO-A gene, while in Caucasians this indicator does not exceed 40%. However, Lee himself admits that blaming all social problems — such as aggressiveness, gambling addiction and various addictions — on a single gene would be an oversimplification.

In another study, using magnetic resonance imaging of the brain, it was demonstrated that carriers of the "militant" MAO-A allele are significantly more excited by a special part of the brain - the amygdala — in response to the presentation of emotional stimuli, such as images of scary or disgusting faces. (The amygdala, or amygdala, is the part of the brain that processes socially significant information related to emotions such as fear and distrust.) The detected activity obviously proves that it is more difficult for such people to control their emotions, and that they are more likely to respond with aggression to any emotional stimuli.

In the case of the MAO-A gene, as well as for the serotonin transporter, it was shown that the owners of the "militant" allele are more likely to have "behavior problems" if they experienced abuse in childhood (and if not, the probability of "antisociality" is almost three times lower) [7]. How events from the sphere of human relationships — even such unpleasant ones as child abuse — are able to influence gene expression — still seems to remain a mystery.

Testosterone acts similarly to the "fly in the ointment" in the case of "antisocial" behavior: when comparing 45 male alcoholics, and even with a criminal past, with a control group "without aggravating factors", it turned out that the "brawlers" not only have reduced expression of MAO-A (i.e. there is a "militant" allele), but also the testosterone content is increased. And although the "militant gene" is hardly responsible for the entire spectrum of social problems, it definitely has some influence on behavior (especially in a "cocktail" with testosterone).

Live fast, die youngWhat unites Janis Joplin, Jimi Hendrix and Kurt Cobain besides the fact that they are all members of the mystically famous club 27?

The world of rock musicians is, perhaps, a good place to find people with a broken (and sometimes completely moved out) a system of positive reinforcements that forms the traditional scale of human values. In the case of such a violation, a person ceases to receive positive emotions from everyday things that are pleasant to most people, and goes all out in search of unhealthy forms of new sensations like addiction to alcohol, tobacco, drugs or gambling. However, is the dopamine receptor responsible for this, reacting to the neurotransmitter dopamine, the lack of which leads to a violation of the system of positive reinforcements?

The allele form A1 of the dopamine receptor D2 does not "feel" dopamine very well, which may lead to a "blunting" of sensations accompanying everyday actions. Some scientists believe that it is the polymorphism of the D2 receptor that causes harmful habits and a clearly expressed constant search for thrills, as well as antisocial behavior, including problems in relationships with other people.

A study involving 195 students from one of the universities of New York State showed that carriers of the A1 allele begin sexual life earlier, but at the same time are less capable of starting long-term relationships. In another work, it was shown that boys — carriers of one A1 allele — have a greater tendency to marginal and criminal behavior than owners of two A2 alleles. However, heterozygous A1/A2 "test subjects" demonstrated an even greater propensity of this kind, somewhat confusing the situation. One scientist even expressed about this gene that "there is still more smoke than fire."

By the way, in the latest issue of Science, there was even a paper in which links are made between variants of the DRD2 gene and adherence to a certain political party, arguing that people with two "highly effective" A2 alleles are more trusting and easier to join any party [8].

It is clear that practically nothing is yet clear in the genetics of behavior. However, it is also clear that psychologists will soon have to arm themselves with modern tools to analyze the genetic characteristics of the participants in their research, in addition to outdated Eysenck tests and other questionnaires.

Prepared based on the materials of Science news [9] with abbreviations.Literature

Biomolecule: "Proteins that "stick together" in Huntington's disease have been identified";

2. Donaldson Z.R., Young L.J. (2008). Oxytocin, vasopressin, and the neurogenetics of sociality. Science 322, 900–904;
3. Elements: "Genes control behavior, and behavior — genes";
4. Walum H. et al. (2008). Genetic variation in the vasopressin receptor 1a gene (AVPR1A) associates with pair-bonding behavior in humans. Proc. Natl. Acad. Sci. U.S.A. 105, 14153–14156;
5. Knafo A. et al. (2008). Individual differences in allocation of funds in the dictator game associated with length of the arginine vasopressin 1a receptor RS3 promoter region and correlation between RS3 length and hippocampal mRNA. Genes Brain Behav. 7, 266–275;
6. Lesch K.P. et al. (1996). Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region. Science 274, 1527–1531;
7. Caspi A. et al. (2002). Role of genotype in the cycle of violence in maltreated children. Science 297, 851–854;
8. Fowler J.H., Schreiber D. (2008). Biology, politics, and the emerging science of human nature. Science 322, 912–914;
9. Holden C. (2008). Parsing the Genetics of Behavior. Science 322, 892–295.

Portal "Eternal youth" www.vechnayamolodost.ru13.11.2008