Gene-Gene Interactions

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Genes are always operating within the micro-environment of the cell, which is influenced by the expression of other genes.  In addition, an environmental exposure could trigger the expression of a gene that in turn modifies other genes. The underlying DNA sequence is not usually altered, but molecular changes occur that affect transcription or translation.

For example, new research suggests one gene-gene interaction model for the increased risk of depression among heavy alcohol users.

  • What typically happens is that a gene called TACE activates a second gene, called MTHFR, which produces an enzyme involved in metabolism of folate, which helps determine the level of folate in the body.
  • If MTHFR is not producing the enzyme at the typical level, folate levels are reduced.  Reduced folate levels are associated with depression.
  • Excessive alcohol exposure has been shown to suppress the TACE gene, which then activates less MTHFR, which then makes less enzyme.  This cascade results in less folate being metabolized, which has been associated with increased incidence of depression.
There are many other examples of gene-gene interactions.  In many cases, there are initiating environmental factors that start the cascade.

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