ADHD Gene #3: Dopamine Transporter Gene (DAT, SLC6A3), Human Chromosome #5
There have been a number of recent postings on genes thought to be connected with ADHD. Previous ones discussed include the ADHD form of the Dopamine D4 receptor Gene (DRD4), the ADHD form of the Dopamine D5 Receptor Gene (DRD5), and, to a lesser degree, the DRD2 ADHD gene. However, one of the most intriguing ADHD genes is a gene called the Dopamine Transporter Gene, abbreviated as DAT. An ADHD form (also called allele), of this gene, which is located on the 5th chromosome in humans, has been tabbed. The ADHD gene DAT has been discussed in another recent post, where it has been tied to a mutated form of a protein called the dopamine transporter protein that "shuttles" an important brain chemical, called dopamine, in and out of neuron cells. While the regular form of this protein functions, normally, the mutated form causes it to run in the opposite direction at high speed, significantly changing the distribution of the dopamine chemical throughout the brain. This balance can result in extreme ADHD symptoms, and has also been seen in bipolar individuals.
Statistically speaking, there is a weaker correlation between the above form of the gene and ADHD behavior than the previous two genes. Nevertheless, this gene serves as an important target for stimulant medications (such as Ritalin) for both rats and humans. A number of studies have been done on an analogous gene in mice has shown that altering this gene function resulted in a noticeable increase in hyperactivity and decrease in behavioral inhibition and control.
Remember, two ADHD genes mentioned in previous posts, the DRD4 ADHD gene, and the DRD5 ADHD gene are both thought to be more affiliated with the inattentive component of ADHD. In contrast, individuals with the DAT gene mentioned in this posting, above are more prone to hyperactivity and behavioral inhibition problems associated with ADHD. We will soon discuss the various components and subtypes of ADD and ADHD in later posts, but for now, please keep in mind that a number of different genes may be at work within and ADHD individual.
There is still a fair amount of research to be done on this gene, but for now, we can cautiously assume that there is a correlation between forms of this DAT gene, located on the 5th human chromosome, and ADHD.
Friday, September 5, 2008