What are the genetic changes related to childhood myocerebrohepatopathy spectrum ?
MCHS is caused by mutations in the POLG gene. This gene provides instructions for making one part, the alpha subunit, of a protein called polymerase gamma (pol ). Pol  functions in mitochondria, which are structures within cells that use oxygen to convert the energy from food into a form cells can use. Mitochondria each contain a small amount of DNA, known as mitochondrial DNA (mtDNA), which is essential for the normal function of these structures. Pol  "reads" sequences of mtDNA and uses them as templates to produce new copies of mtDNA in a process called DNA replication.  Most POLG gene mutations change single protein building blocks (amino acids) in the alpha subunit of pol . These changes result in a mutated pol  that has a reduced ability to replicate DNA. Although the mechanism is unknown, mutations in the POLG gene often result in fewer copies of mtDNA (mtDNA depletion), particularly in muscle, brain, or liver cells. MtDNA depletion causes a decrease in cellular energy, which could account for the signs and symptoms of MCHS.