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Test Code POLG1 SEQ POLG1 Sequencing

Clinical System Name

Polymerase Gamma 1 Sequencing Analysis Request

Description

Mutations in the gene encoding polymerase gamma, POLG1, cause mtDNA depletion or multiple mtDNA deletions resulting in a highly heterogeneous group of mitochondrial diseases.

 

POLG1 DNA sequencing is appropriate for individuals with any of the following:

  • Progressive external opthalmoplegia
  • Cerebellar ataxia ± seizures
  • Acute liver failure
  • Multiple mtDNA deletions or mtDNA depletion in affected tissues
  • Cytochrome oxidase (COX)-deficient muscle fibers

Sample Requirements

Specimen: Whole blood, cord blood

Container(s): Lavender/EDTA, Yellow/ACD A or B

Preferred Vol: 3 mL

Minimum Vol: 1 mL

 

Note: Heparin samples (Green tops) are unacceptable.

 

Specimen: Extracted DNA

Minimum: 10µg

Note: DNA concentration minimum 50 µg/mL; 260/280 ratio 1.70-2.00

  

Specimen: Cultured cells

Acceptable:  Fibroblasts

Container(s): T-25 flasks

Preferred Vol: 2 flasks

Processing Instructions

Reject due to: Heparin

Spin: No

Aliquot: No

Temp: Refrigerate

Storage location: Molecular Genetics box in CPA refrigerator #2

 

Off-site collection: Refrigerate blood samples until ready to ship.  Transport all sample types at room temperature via overnight shipping.

Stability

Specimen Type Temperature Time
Cultured cells Room temp 3 days
Whole blood, extracted DNA Room temp 3-5 days
Whole blood, extracted DNA Refrigerated 7 days
Extracted DNA Frozen ok

 

Note: Whole blood samples > 7days may be submitted to be assessed by our lab for acceptability for testing.

Availability

STAT Performed TAT
Contact lab Monday - Friday 2-3 weeks

 

Performing Laboratory

Seattle Children's Laboratory

Department

Department:  Molecular Genetics Laboratory

Phone: 206-987-3872

 

Lab Client Services: 206-987-2617

 

Lab Genetic Counselor: LabGC@seattlechildrens.org

Reference Range

Interpretive report will be provided

Methodology

Method: Bi-directional sequencing of all exons and exon-intron boundaries

 

Limitations: Mutations in the promoter region, large deletions, large duplications, or rare recombinant mutations may not be detected by this method.

CPT Codes

81406 (updated 1/20/16 by jconta)

Special Instructions

Links to: POLG-Related Disorders GeneReview

Requisition

Molecular Genetics

Clinical Utility

DNA polymerase gamma is the only DNA polymerase found in the mitochondria and is responsible for mtDNA replication and repair. Mutations in the gene encoding polymerase gamma, POLG1, cause mtDNA depletion or multiple mtDNA deletions resulting in a highly heterogeneous group of mitochondrial diseases. POLG1 mutations may account for up to 25% of all adult onset mitochondrial disease. POLG1 mutations have been described in Progressive External Ophthalmoplegia both autosomal dominant and recessive forms, parkinsonism and premature menopause, adult onset cerebellar ataxia, Sensory Ataxia Neuropathy with Opthalmoparesis (SANDO), Alpers Syndrome (childhood onset progressive spastic quadriparesis, progressive cerebral degeneration and liver failure) and other childhood or adulthood onset ataxia syndromes with and without seizures.