DGUOK-Related Hepatocerebral Form of Mitochondrial DNA Depletion Syndrome via the DGUOK Gene

  • Summary and Pricing
  • Clinical Features and Genetics
  • Citations
  • Methods
  • Ordering/Specimens
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Test Code Test Copy GenesIndividual Gene PriceCPT Code Copy CPT Codes
1243 DGUOK$650.00 81405 Add to Order
Targeted Testing

For ordering targeted known variants, please proceed to our Targeted Variants landing page.

Turnaround Time

The great majority of tests are completed within 18 days.

Clinical Sensitivity

Clinical sensitivity is difficult to predict accurately for DGUOK-related hepatocerebral mtDNA depletion syndrome, as cases are rare. However, several small cohorts have been studied. Al-Hussaini et al. reported that four of 20 infants (20%) with a suspected diagnosis of hepatocerebral mtDNA depletion syndrome carried pathogenic variants in DGUOK (Al-Hussaini et al. 2014). Additionally, in a cohort of 20 Japanese patients with the more general diagnosis of mtDNA depletion syndrome, Yamazaki et al. identified three patients (15%) with DGUOK defects (Yamazaki et al. 2014).

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Deletion/Duplication Testing via aCGH

Test Code Test Copy GenesIndividual Gene PriceCPT Code Copy CPT Codes
600 DGUOK$690.00 81479 Add to Order
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Turnaround Time

The great majority of tests are completed within 28 days.

Clinical Features

Mitochondrial DNA Depletion Syndromes (MDSs) are a group of clinically and genetically heterogeneous diseases characterized by a quantitative abnormality of the mitochondrial genome in specific tissues (Suomalainen and Isohanni 2010; El-Hattab and Scaglia 2013). Patients with the hepatocerebral form of MDS commonly develop severe hepatopathy, hypotonia, and psychomotor delay.

The DGUOK-related hepatocerebral form of MDS can be classified into two subgroups depending on age of onset and organ involvement. The majority of patients present with the neonatal-onset, multi-organ form of disease, while the remaining patients present with an isolated hepatic disease later in infancy or childhood (El-Hattab and Scaglia 2013; Scaglia et al. 2009). Progressive hepatic dysfunction is the most common cause of death for this disorder regardless of age at onset.

Individuals with the neonatal-onset, multi-organ form of DGUOK-associated MDS present with lactic acidosis and hypoglycemia in the first week of life, rapidly followed by the development of hepatic disease and neurologic dysfunction (Scaglia et al. 2009). Other clinical features include typical rotary nystagmus, developmental regression, severe myopathy and cholestasis. Liver failure occurs at the neonatal or infantile stage, in combination with ascites, edema, and coagulopathy.

In contrast, the isolated hepatic form of disease results in mild hypotonia and renal involvement, which may manifest as proteinuria and aminoaciduria (Dimmock et al. 2008). Less frequently reported characteristics include neonatal hemochromatosis and adult-onset mitochondrial myopathy occasionally accompanied by progressive external ophthalmoplegia (PEO) (Hanchard et al. 2011; Ronchi et al. 2012).


The DGUOK -related hepatocerebral form of MDS is an autosomal recessive disorder caused by pathogenic variants in the DGUOK gene (Mandel et al. 2001). DGUOK spans 7 coding exons and encodes for a mitochondrial deoxyguanosine kinase that plays an essential role in the purine nucleoside salvage pathway. Missense, nonsense, and splicing variants, in addition to small deletion and insertions, have been found across the entire coding region of DGUOK. Several large deletions have also been reported (Wang et al. 2012; Mudd et al. 2012; Lee et al. 2009; Yamazaki et al. 2014).

The hepatocerebral form of MDS can also be caused by defects in POLG, MPV17 and C10orf2 (El-Hattab and Scaglia 2013).

Testing Strategy

Full gene sequencing of DGUOK is performed, with bidirectional sequencing of exons 1-7. The full coding region of each exon plus ~20 bp of flanking non-coding DNA on either side are sequenced. We also sequence the documented splicing variant c.444-62C>A, which was reported as a founder mutation in a North African population (Brahimi et al. 2009). We will also sequence any single exon (Test #100) or pair of exons (Test #200) in family members of patients with a known pathogenic variant or to confirm research results.

Indications for Test

Candidates for this test are patients with the hepatocerebral form of MDS. Testing is also indicated for family members of patients who have known DGUOK mutations.


Official Gene Symbol OMIM ID
DGUOK 601465
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Related Test

Mitochondrial Genome Maintenance/Integrity Nuclear Genes Sequencing Panel


Genetic Counselors
  • Al-Hussaini A. et al. 2014. The Journal of Pediatrics. 164: 553-9.e1-2. PubMed ID: 24321534
  • Brahimi N. et al. 2009. Molecular Genetics and Metabolism. 97:221-6. PubMed ID: 19394258
  • Dimmock D.P. et al. 2008. Liver Transplantation : Official Publication of the American Association For the Study of Liver Diseases and the International Liver Transplantation Society. 14: 1480-5. PubMed ID: 18825706
  • El-Hattab A. and Scaglia F. 2013. Neurotherapeutics. 10:186-98.  PubMed ID: 23385875
  • Hanchard N.A. et al. 2011. Molecular Genetics and Metabolism. 103: 262-7. PubMed ID: 21478040
  • Lee N.C. et al. 2009. Archives of Disease in Childhood. 94:55-8. PubMed ID: 19103789
  • Mandel H. et al. 2001. Nature Genetics. 29:337-41. PubMed ID: 11687800
  • Mudd S.H. et al. 2012. Molecular Genetics and Metabolism. 105:228-36. PubMed ID: 22137549
  • Ronchi D. et al. 2012. Brain : a Journal of Neurology. 135: 3404-15. PubMed ID: 23043144
  • Scaglia F. et al. 2009. DGUOK-related mitochondrial DNA depletion syndrome, hepatocerebral form. In: Pagon RA, Adam MP, Bird TD, Dolan CR, Fong C-T, Smith RJ, and Stephens K, editors. GeneReviews(®), Seattle (WA): University of Washington, Seattle. PubMed ID: 20301766
  • Suomalainen A. and Isohanni P. 2010. Neuromuscular Disorders. 20:429-37. PubMed ID: 20444604
  • Wang J. et al. 2012. Molecular Genetics and Metabolism. 106:221-30. PubMed ID: 22494545
  • Yamazaki T. et al. 2014. Pediatrics International : Official Journal of the Japan Pediatric Society. 56: 180-7. PubMed ID: 24266892
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Bi-Directional Sanger Sequencing

Test Procedure

Nomenclature for sequence variants was from the Human Genome Variation Society (  As required, DNA is extracted from the patient specimen.  PCR is used to amplify the indicated exons plus additional flanking non-coding sequence.  After cleaning of the PCR products, cycle sequencing is carried out using the ABI Big Dye Terminator v.3.0 kit.  Products are resolved by electrophoresis on an ABI 3730xl capillary sequencer.  In most cases, sequencing is performed in both forward and reverse directions; in some cases, sequencing is performed twice in either the forward or reverse directions.  In nearly all cases, the full coding region of each exon as well as 20 bases of non-coding DNA flanking the exon are sequenced.

Analytical Validity

As of March 2016, we compared 17.37 Mb of Sanger DNA sequence generated at PreventionGenetics to NextGen sequence generated in other labs. We detected only 4 errors in our Sanger sequences, and these were all due to allele dropout during PCR. For Proficiency Testing, both external and internal, in the 12 years of our lab operation we have Sanger sequenced roughly 8,800 PCR amplicons. Only one error has been identified, and this was due to sequence analysis error.

Our Sanger sequencing is capable of detecting virtually all nucleotide substitutions within the PCR amplicons. Similarly, we detect essentially all heterozygous or homozygous deletions within the amplicons. Homozygous deletions which overlap one or more PCR primer annealing sites are detectable as PCR failure. Heterozygous deletions which overlap one or more PCR primer annealing sites are usually not detected (see Analytical Limitations). All heterozygous insertions within the amplicons up to about 100 nucleotides in length appear to be detectable. Larger heterozygous insertions may not be detected. All homozygous insertions within the amplicons up to about 300 nucleotides in length appear to be detectable. Larger homozygous insertions may masquerade as homozygous deletions (PCR failure).

Analytical Limitations

In exons where our sequencing did not reveal any variation between the two alleles, we cannot be certain that we were able to PCR amplify both of the patient’s alleles. Occasionally, a patient may carry an allele which does not amplify, due for example to a deletion or a large insertion. In these cases, the report contains no information about the second allele.

Similarly, our sequencing tests have almost no power to detect duplications, triplications, etc. of the gene sequences.

In most cases, only the indicated exons and roughly 20 bp of flanking non-coding sequence on each side are analyzed. Test reports contain little or no information about other portions of the gene, including many regulatory regions.

In nearly all cases, we are unable to determine the phase of sequence variants. In particular, when we find two likely causative mutations for recessive disorders, we cannot be certain that the mutations are on different alleles.

Our ability to detect minor sequence variants, due for example to somatic mosaicism is limited. Sequence variants that are present in less than 50% of the patient’s nucleated cells may not be detected.

Runs of mononucleotide repeats (eg (A)n or (T)n) with n >8 in the reference sequence are generally not analyzed because of strand slippage during PCR and cycle sequencing.

Unless otherwise indicated, the sequence data that we report are based on DNA isolated from a specific tissue (usually leukocytes). Test reports contain no information about gene sequences in other tissues.

Deletion/Duplication Testing via Array Comparative Genomic Hybridization

Test Procedure

Equal amounts of genomic DNA from the patient and a gender matched reference sample are amplified and labeled with Cy3 and Cy5 dyes, respectively. To prevent any sample cross contamination, a unique sample tracking control is added into each patient sample. Each labeled patient product is then purified, quantified, and combined with the same amount of reference product. The combined sample is loaded onto the designed array and hybridized for at least 22-42 hours at 65°C. Arrays are then washed and scanned immediately with 2.5 µM resolution. Only data for the gene(s) of interest for each patient are extracted and analyzed.

Analytical Validity

PreventionGenetics' high density gene-centric custom designed aCGH enables the detection of relatively small deletions and duplications within a single exon of a given gene or deletions and duplications encompassing the entire gene. PreventionGenetics has established and verified this test's accuracy and precision.

Analytical Limitations

Our dense probe coverage may allow detection of deletions/duplications down to 100 bp; however due to limitations and probe spacing this cannot be guaranteed across all exons of all genes. Therefore, some copy number changes smaller than 100-300 bp within a targeted large exon may not be detected by our array.

This array may not detect deletions and duplications present at low levels of mosaicism or those present in genes that have pseudogene copies or repeats elsewhere in the genome.

aCGH will not detect balanced translocations, inversions, or point mutations that may be responsible for the clinical phenotype.

Breakpoints, if occurring outside the targeted gene, may be hard to define.

The sensitivity of this assay may be reduced when DNA is extracted by an outside laboratory.

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Ordering Options

myPrevent - Online Ordering
  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.


(Delivery accepted Monday - Saturday)

  • Collect 3 ml -5 ml (5 ml preferred) of whole blood in EDTA (purple top tube) or ACD (yellow top tube). For Test #500-DNA Banking only, collect 10 ml -20 ml of whole blood.
  • For small babies, we require a minimum of 1 ml of blood.
  • Only one blood tube is required for multiple tests.
  • Ship blood tubes at room temperature in an insulated container. Do not freeze blood.
  • During hot weather, include a frozen ice pack in the shipping container. Place a paper towel or other thin material between the ice pack and the blood tube.
  • In cold weather, include an unfrozen ice pack in the shipping container as insulation.
  • At room temperature, blood specimen is stable for up to 48 hours.
  • If refrigerated, blood specimen is stable for up to one week.
  • Label the tube with the patient name, date of birth and/or ID number.


(Delivery accepted Monday - Saturday)

  • Send in screw cap tube at least 5 µg -10 µg of purified DNA at a concentration of at least 20 µg/ml for NGS and Sanger tests and at least 5 µg of purified DNA at a concentration of at least 100 µg/ml for gene-centric aCGH, MLPA, and CMA tests, minimum 2 µg for limited specimens.
  • For requests requiring more than one test, send an additional 5 µg DNA per test ordered when possible.
  • DNA may be shipped at room temperature.
  • Label the tube with the composition of the solute, DNA concentration as well as the patient’s name, date of birth, and/or ID number.
  • We only accept genomic DNA for testing. We do NOT accept products of whole genome amplification reactions or other amplification reactions.


(Delivery preferred Monday - Thursday)

  • PreventionGenetics should be notified in advance of arrival of a cell culture.
  • Culture and send at least two T25 flasks of confluent cells.
  • Some panels may require additional flasks (dependent on size of genes, amount of Sanger sequencing required, etc.). Multiple test requests may also require additional flasks. Please contact us for details.
  • Send specimens in insulated, shatterproof container overnight.
  • Cell cultures may be shipped at room temperature or refrigerated.
  • Label the flasks with the patient name, date of birth, and/or ID number.
  • We strongly recommend maintaining a local back-up culture. We do not culture cells.
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