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RRM2B gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

RRM2B gene

The RRM2B gene provides instructions for a protein subunit that helps produce DNA building blocks, particularly within mitochondria.

Normal Function

The RRM2B gene provides instructions for making one piece, called the p53 inducible small subunit (p53R2), of a protein called ribonucleotide reductase (RNR). Two copies of the p53R2 subunit attach to two copies of another protein called R1 to form RNR. RNR helps produce DNA building blocks (nucleotides), which are joined to one another to form DNA.

RNRs containing p53R2 make nucleotides used for the formation of DNA in specialized cell structures called mitochondria. Mitochondria are the energy-producing centers in cells, and the DNA in these structures (mtDNA) contains genes essential for energy production (oxidative phosphorylation). The production of nucleotides by p53R2 helps maintain a normal amount of mtDNA in cells.

Health Conditions Related to Genetic Changes

Progressive external ophthalmoplegia

At least 17 mutations in the RRM2B gene have been identified in people with progressive external ophthalmoplegia. This disorder weakens the muscles that control eye movement and causes the eyelids to droop (ptosis). Some affected individuals have additional signs and symptoms, such as weakness of other muscles, extreme tiredness (fatigue), hearing loss, and digestive problems.

These mutations lead to impaired RNR activity, resulting in large deletions of genetic material from mtDNA in muscle tissue. It has been suggested that eye muscles are commonly affected by mitochondrial defects because they are especially dependent on oxidative phosphorylation for energy.

RRM2B-related mitochondrial DNA depletion syndrome

More than a dozen mutations in the RRM2B gene can cause RRM2B-related mitochondrial DNA depletion syndrome (RRM2B-MDS), a severe condition that affects multiple body systems. It typically leads to brain dysfunction combined with muscle weakness (encephalomyopathy) and a problem with kidney function known as renal tubulopathy.

The mutations that cause this disorder occur in both copies of the RRM2B gene. They reduce the activity or amount of RNR, which impairs the production of mtDNA nucleotides. A shortage of these nucleotides leads to a reduction in the amount of mtDNA (mtDNA depletion) and impairs mitochondrial function in many different types of cells.

Other Names for This Gene

  • MTDPS8A
  • MTDPS8B
  • p53-inducible ribonucleotide reductase small subunit 2 homolog
  • p53-inducible ribonucleotide reductase small subunit 2 short form beta
  • p53-inducible ribonucleotide reductase small subunit 2-like protein
  • P53R2
  • ribonucleoside-diphosphate reductase subunit M2 B isoform 1
  • ribonucleoside-diphosphate reductase subunit M2 B isoform 2
  • ribonucleoside-diphosphate reductase subunit M2 B isoform 3
  • ribonucleotide reductase M2 B (TP53 inducible)
  • TP53-inducible ribonucleotide reductase M2 B

Frequently Asked Questions

For progressive external ophthalmoplegia (PEO), early signs often include drooping eyelids (ptosis) and weakness of the muscles controlling eye movement. In RRM2B-related mitochondrial DNA depletion syndrome (MDS), which is more severe, symptoms typically appear early in life and can affect multiple body systems, potentially including muscle weakness, developmental delays, and organ dysfunction, though specific initial symptoms can vary.
Eye muscles are commonly affected in RRM2B-related progressive external ophthalmoplegia because they have a high energy demand and are particularly sensitive to defects in mitochondrial function. The RRM2B gene is crucial for maintaining
There is currently no cure for RRM2B-related mitochondrial disorders. Treatment focuses on managing symptoms and providing supportive care. This can include physical therapy for muscle weakness, surgical correction for ptosis, hearing aids for hearing loss, and nutritional support for digestive issues. For severe cases like RRM2B-MDS, comprehensive multidisciplinary care is essential to address the various affected body systems.
Diagnosis involves a combination of clinical evaluation of symptoms, muscle biopsies to look for mitochondrial abnormalities and mtDNA deletions, and genetic testing to identify specific mutations in the RRM2B gene. Blood tests and neuroimaging may also be used to assess the extent of the disorder.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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