What are the genetic changes related to 2-hydroxyglutaric aciduria ?
The different types of 2-hydroxyglutaric aciduria result from mutations in several genes. D-2-HGA type I is caused by mutations in the D2HGDH gene; type II is caused by mutations in the IDH2 gene. L-2-HGA results from mutations in the L2HGDH gene. Combined D,L-2-HGA is caused by mutations in the SLC25A1 gene.  The D2HGDH and L2HGDH genes provide instructions for making enzymes that are found in mitochondria, which are the energy-producing centers within cells. The enzymes break down compounds called D-2-hydroxyglutarate and L-2-hydroxyglutarate, respectively, as part of a series of reactions that produce energy for cell activities. Mutations in either of these genes lead to a shortage of functional enzyme, which allows D-2-hydroxyglutarate or L-2-hydroxyglutarate to build up in cells. At high levels, these compounds can damage cells and lead to cell death. Brain cells appear to be the most vulnerable to the toxic effects of these compounds, which may explain why the signs and symptoms of D-2-HGA type I and L-2-HGA primarily involve the brain.  The IDH2 gene provides instructions for making an enzyme in mitochondria that normally produces a different compound. When the enzyme is altered by mutations, it takes on a new, abnormal function: production of the potentially toxic compound D-2-hydroxyglutarate. The resulting excess of this compound damages brain cells, leading to the signs and symptoms of D-2-HGA type II. It is unclear why an accumulation of D-2-hydroxyglutarate may be associated with cardiomyopathy in some people with this form of the condition.  The SLC25A1 gene provides instructions for making a protein that transports certain molecules, such as citrate, in and out of mitochondria. Mutations in the SLC25A1 gene reduce the protein's function, which prevents it from carrying out this transport. Through processes that are not fully understood, a loss of this transport allows both D-2-hydroxyglutarate and L-2-hydroxyglutarate to build up, which damages brain cells. Researchers suspect that an imbalance of other molecules, particularly citrate, also contributes to the severe signs and symptoms of combined D,L-2-HGA.