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TIMM8A gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

TIMM8A gene

The TIMM8A gene provides instructions for creating a protein vital for mitochondrial function, with mutations linked to deafness-dystonia-optic neuronopathy syndrome.

Normal Function

The TIMM8A gene provides instructions for making a protein that is found inside mitochondria, which are structures within cells that convert the energy from food into a form that cells can use. Mitochondria have two membranes, an outer membrane and an inner membrane, which are separated by a fluid-filled area called the intermembrane space. The TIMM8A protein is found in the intermembrane space, where it forms a complex (a group of proteins that work together) with a very similar protein called TIMM13. This complex transports other proteins across the intermembrane space to the mitochondrial inner membrane.

Health Conditions Related to Genetic Changes

Deafness-dystonia-optic neuronopathy syndrome

At least 20 mutations in the TIMM8A gene have been found to cause deafness-dystonia-optic neuronopathy (DDON) syndrome. Most of these mutations result in the absence of functional TIMM8A protein inside the mitochondria, which prevents the formation of the TIMM8A/TIMM13 complex. Researchers believe that the lack of this complex leads to abnormal transport of proteins across the intermembrane space, although it is unclear how abnormal protein transport affects the function of the mitochondria and causes the signs and symptoms of DDON syndrome.

Some people with DDON syndrome have large DNA deletions that remove the entire TIMM8A gene and one end of a neighboring gene known as BTK. Mutations in the BTK gene cause X-linked agammaglobulinemia (XLA), which is characterized by an increased susceptibility to infections. Individuals with large DNA deletions that include the TIMM8A gene and the BTK gene have the signs and symptoms of both DDON syndrome and XLA.

Other Names for This Gene

  • DDP
  • DDP1
  • deafness/dystonia peptide
  • DFN1
  • MGC12262
  • TIM8A_HUMAN
  • translocase of inner mitochondrial membrane 8 homolog A
  • translocase of inner mitochondrial membrane 8 homolog A (yeast)

Frequently Asked Questions

Diagnosis begins with clinical features: progressive sensorineural hearing loss, movement‑disorder (dystonia), and optic nerve atrophy. Genetic confirmation is essential; sequencing of the TIMM8A gene (or a targeted panel for mitochondrial disorders) identifies pathogenic variants or deletions. In cases where a large deletion also removes the neighboring BTK gene, additional immunologic testing for X‑linked agammaglobulinemia is performed. Genetic confirmation guides counseling and eligibility for clinical trials.
Currently, there is no disease‑modifying therapy for DDON. Management is symptomatic: hearing aids or cochlear implants for deafness, physical therapy and medications (e.g., baclofen, trihexyphenidyl) for dystonia, and low‑vision aids for optic neuropathy. Early intervention with multidisciplinary rehabilitation can preserve function and quality of life. Research into mitochondrial‑targeted antioxidants and gene‑replacement strategies is ongoing but not yet clinically available.
Yes. Because TIMM8A mutations are X‑linked, carrier testing for female relatives and prenatal or pre‑implantation testing for at‑risk pregnancies are options. Counseling explains inheritance patterns (males are typically affected, females can be carriers), variability of disease severity, and reproductive choices. A certified genetic counselor can also discuss the possibility of testing for the adjacent BTK gene if a large deletion is present.
When the BTK gene is also deleted, the child is at risk for X‑linked agammaglobulinemia, which leads to very low B‑cell numbers and recurrent bacterial infections. Regular immunologic evaluation (quantitative immunoglobulins, vaccine response testing) is recommended. Prophylactic antibiotics or immunoglobulin replacement therapy may be needed. Coordination between neurology, immunology, and genetics is essential to address both DDON and immune deficiency.
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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