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Writer's pictureAlexis Billings

Genetics Could Control Aggression: The Warrior Gene

What is the "Warrior Gene"?


The Warrior Gene is the common name for the MAO-A gene, monoamine oxidase A, which is part of the MAO family of enzymes. This gene is found on the X chromosome. Wild-type expression of the gene causes dopamine, serotonin, and norepinephrine to be catabolized by the enzyme gene product. Due to the mutation in this MAO-A gene, there is an accumulation of serotonin. Normally, one would think this sounds like a good thing since serotonin is usually associated with happiness and emotions. However, too much of this neurotransmitter will cause highly aggressive and impulsive behaviors.


What is Brunner Syndrome?


Brunner Syndrome is caused by a deficiency of the MAO-A gene product. The syndrome was first discovered by H. G. Brunner while he was observing the behavior of members of a Dutch family. In this family he noticed that these aggressive and impulsive behaviors occurred exclusively in the male members, and they all lacked a functional monoamine oxidase A enzyme due to a point mutation. Since the gene is found on the X chromosome, this would explain why the syndrome is almost never seen in females: the syndrome follows an X-linked recessive inheritance pattern, meaning males only need one copy of this mutation to express the abnormal behaviors, while females require two copies to express the aggression and impulsivity associated with the deficiency.


It has been noted that with this syndrome, there are also other side effects possible. These side effects include other mental disorders, such as autism or ADHD, while also having more obvious physical symptoms. These physical symptoms include skin flushing and diarrhea, along with other integumentary or gastric issues. Females who have had this MAO-A deficiency experienced the physical symptoms, but did not show the other mental symptoms of having this disorder. These symptoms are mainly expressed in males.


How does environment affect the gene?


While genetics does handle a lot of how the body and mind function, it cannot be denied that environment influences these aspects too. Studies looking into the exact function of this gene and how it changes behavior started in mice. Mice with the MAO-A gene knocked out had more aggressive tendencies than mice with the wild-type. Later studies were done to possibly relate the mutant gene to childhood development. Maltreated and abused children with the mutant MAO-A gene had more intense behavioral problems during adulthood. Early trauma and parenting could potentially have mediating roles in the abnormal behavior caused by this gene. These factors could be related to epigenetic regulation of serotonin, especially in females due to the lack of data for expression in them.


Is the "Warrior Gene" a concern?


While having a deficiency of the MAO-A gene product causes aggressive and antisocial behaviors, the changes in behavior are not uncontrollable for the affected individual. The mutant MAO-A gene simply makes those with the deficiency more susceptible to forming these aggressive and impulsive behaviors. Environmental factors, such as abuse and maltreatment, will cause an individual with this deficiency to be more likely to develop these abnormal behaviors. It is not immediately set in stone that they will develop the intense aggressive behaviors associated with the disorder. However, research on this gene needs to increase to establish how it affects a multitude of people. Specifically, more research is necessary to determine how this gene is expressed in females and individuals of different ethnicities. If more research is done on this gene and early childhood care improves, the expression of this gene should be diminished significantly.



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