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Diagnostic Services

Genetics Lab


Progressive External Opthalmoplegia (POLG-2) Sequencing

DNA polymerase gamma is the only DNA polymerase found in the mitochondria and is responsible for maintaining the integrity of the mitochondrial genome by mtDNA replication and repair. DNA polymerase gamma is composed of a catalytic subunit (POLG1) and an accessory subunit (POLG2). POLG2 enhances the affinity of the DNA polymerase gamma to bind to DNA. Mutations in POLG2 lead to a failure to enhance the DNA-binding strength which stalls the DNA replication fork causing mtDNA deletions to arise. The progressive accumulation of the mtDNA deletions causes cytochrome c oxidase (COX) deficiency in muscle fibers, primarily external eye muscles and skeletal muscle. Autosomal dominant progressive external ophthalmoplegia with mtDNA deletions (PEO4) is characterized by adult-onset weakness of the external eye muscles (leading to ptosis), mild weakness of facial muscles and exercise intolerance.

Test Name: Polymerase Gamma 2 Sequencing Analysis
Test Code:
Test Description:
Polymerase Chain Reaction (PCR) followed by sequence analysis of the entire coding region of the POLG2 gene
Autosomal Dominant Progressive External Ophthalmoplegia with mtDNA Deletions (PEOA4)
POLG1 DNA sequencing is appropriate for individuals with progressive external opthalmoplegia with:
• Multiple mtDNA deletions in skeletal muscle and/or
• Cytochrome oxidase (COX)-deficient muscle fibers
Related Tests:
Clinical Links:
Mon - Fri
Turnaround Time:
2-3 weeks
PCR followed by sequencing
Reference Range:
Interpretive report will be provided
Consent Form:
Sample Requirements: Type
Whole blood: 1-3 mL in EDTA (purple top) or ACD (yellow top).
DNA: 5 micrograms extracted DNA

Do not spin. Keep at room temperature.

Ship overnight at ambient temperature.
Samples Received:
Monday - Friday 8am - 5pm PST
Special Considerations:
Please e-mail Lab Client Services ( or call at 206-987-2617 with any billing questions
CPT Code:
Please e-mail Lab Client Services ( or call at 206-987-2617 with any billing questions