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MPV17-Related Hepatocerebral Mitochondrial DNA Depletion Syndrome

Includes: Navajo Neurohepatopathy

, MD, FAAP, FACMG, , MD, FACMG, , MD, PhD, FACMG, and , PhD, FACMG.

Author Information
, MD, FAAP, FACMG
Assistant Professor of Child Health and Pathology & Anatomical Sciences
Director of Biochemical Genetics Laboratory
Division of Medical Genetics
Department of Child Health
University of Missouri Health Care
Columbia, Missouri
, MD, FACMG
Associate Professor, Department of Molecular and Human Genetics
Baylor College of Medicine
Houston, Texas
, MD, PhD, FACMG
Professor, Department of Molecular and Human Genetics
Professor, Department of Pediatrics
Director, Metabolic Clinic
Medical Director, Mitochondrial Diagnostic Laboratory
BCM Medical Genetics Laboratories
Baylor College of Medicine
Houston, Texas
, PhD, FACMG
Professor, Department of Molecular and Human Genetics
Director, Mitochondrial Diagnostic Laboratory
BCM Medical Genetics Laboratories
Baylor College of Medicine
Houston, Texas

Initial Posting: .

Summary

Disease characteristics. MPV17-related hepatocerebral mitochondrial DNA (mtDNA) depletion syndrome is characterized by infantile-onset liver dysfunction that typically progresses to liver failure; neurologic involvement (developmental delay, hypotonia, and muscle weakness in the majority; ataxia, seizures, and motor and sensory peripheral neuropathy in some); failure to thrive; and metabolic derangements including lactic acidosis and hypoglycemic crises. Less frequent manifestations include renal tubulopathy, hypoparathyroidism, gastrointestinal dysmotility, and corneal anesthesia. Progressive liver disease often leads to death in infancy or early childhood. Hepatocellular carcinoma has been reported.

Diagnosis/testing. MtDNA content is severely reduced in liver tissue (<20% of controls) and muscle tissue (<30% of controls). Molecular genetic testing of MPV17 detects biallelic mutations in most affected children.

Management. Treatment of manifestations: Ideally management is by a multidisciplinary team including specialists in hepatology, neurology, nutrition, medical genetics, and child development. Nutritional support should be provided by a dietitian experienced in managing children with liver diseases; prevention of hypoglycemia requires frequent feeds and uncooked cornstarch (1-2 grams/kg/dose). Although liver transplantation remains the only treatment option for liver failure, it is controversial because of the multisystem involvement in this disorder.

Prevention of secondary complications: Prevent nutritional deficiencies (e.g., of fat-soluble vitamins) by ensuring adequate intake.

Surveillance: Monitor: liver function to assess progression of liver disease; serum alpha fetoprotein (AFP) concentration and hepatic ultrasound examination for evidence of hepatocellular carcinoma; development, neurologic status, and nutritional status.

Agents/circumstances to avoid: Prolonged fasting.

Genetic counseling. MPV17-related hepatocerebral mtDNA depletion syndrome is inherited in an autosomal recessive manner. Each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if the disease-causing mutations in the family are known.

Diagnosis

Clinical Diagnosis

The diagnosis of MPV17-related hepatocerebral mitochondrial DNA (mtDNA) depletion syndrome should be suspected in infants with a combination of the following:

  • Hepatic manifestations including elevated transaminases, jaundice, cholestasis, hepatomegaly, cirrhosis, and liver failure
  • Neurologic manifestations including developmental delay, hypotonia, muscle weakness, ataxia, motor and sensory peripheral neuropathy, and leukoencephalopathy by brain MRI [Navarro-Sastre et al 2008, Spinazzola et al 2008]
  • Failure to thrive
  • Metabolic derangements including lactic acidosis and severe hypoglycemic crises in early infancy

Testing

Mitochondrial DNA (mtDNA) content (copy number) analysis

  • MtDNA content is severely and consistently reduced in liver tissue (<20% of tissue- and age-matched controls).
  • MtDNA content can also be reduced in muscle tissue (typically <30% of tissue- and age-matched controls).

Note: Mitochondrial DNA copy number values in blood cells are not a reliable indicator of mtDNA depletion [Dimmock et al 2010, El-Hattab et al 2010].

Electron transport chain (ETC) activity. ETC activity assays in liver and muscle tissue of affected individuals typically show decreased activity of multiple complexes with complex I or I+III being the most affected. Similar to the findings of mtDNA content, the liver ETC activities are usually more reduced than those of muscle tissue [El-Hattab et al 2010].

Molecular Genetic Testing

Gene. MPV17, which encodes for a mitochondrial inner membrane protein, is the only gene in which mutations cause MPV17-related hepatocerebral mitochondrial DNA depletion syndrome. (See Table A. Genes and Databases for chromosome locus and protein encoded by this gene.)

Table 1. Summary of Molecular Genetic Testing Used in MPV17-Related Hepatocerebral Mitochondrial Depletion Syndrome

Gene 1Test MethodMutations Detected 2Mutation Detection Frequency by Test Method 3
MPV17Sequence analysisSequence variants 428/31 (90%) 5
Deletion/duplication analysis 6Exonic or whole-gene deletions2/31 (6%) 7

1. See Table A. Genes and Databases for chromosome locus and protein name.

2. See Molecular Genetics for information on allelic variants.

3. The ability of the test method used to detect a mutation that is present in the indicated gene

4. Examples of mutations detected by sequence analysis may include small intragenic deletions/insertions and missense, nonsense, and splice site mutations; typically, exonic or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.

5. Sequencing of all coding exons and the flanking intronic regions identified homozygous or compound heterozygous mutations in 28 of 31 affected individuals [El-Hattab et al 2010, Merkle et al 2012].

6. Testing that identifies deletions/duplications not readily detectable by sequence analysis of the coding and flanking intronic regions of genomic DNA; included in the variety of methods that may be used are: quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and chromosomal microarray (CMA) that includes this gene/chromosome segment.

7. A 1.57-kb deletion spanning exon 8 has been reported in two affected individuals [El-Hattab et al 2010].

Testing Strategy

To confirm/establish the diagnosis in a proband. As a part of the workup of unexplained infantile liver dysfunction, the liver biopsy that is obtained for pathologic examination should also undergo mtDNA content analysis.

The identification of severely reduced mtDNA copy number should prompt further evaluation that includes molecular genetic testing of MPV17:

Carrier testing for at-risk relatives requires prior identification of the disease-causing mutations in the family.

Note: Carriers are heterozygotes for this autosomal recessive disorder and are not at risk of developing the disorder.

Prenatal diagnosis and preimplantation genetic diagnosis (PGD) for at-risk pregnancies require prior identification of the disease-causing mutations in the family.

Clinical Description

Natural History

MPV17-related hepatocerebral mtDNA depletion syndrome, an infantile-onset disorder, can present with a spectrum of combined hepatic, neurologic, and metabolic manifestations. To date, molecularly confirmed MPV17-related hepatocerebral mtDNA depletion syndrome has been reported in 31 individuals [Karadimas et al 2006, Spinazzola et al 2006, Wong et al 2007, Navarro-Sastre et al 2008, Spinazzola et al 2008, Kaji et al 2009, Parini et al 2009, El-Hattab et al 2010, Merkle et al 2012].

Of note, among the 31 confirmed cases are individuals with Navajo neurohepatopathy who were found to have homozygous p.Arg50Gln mutations in MPV17 [Karadimas et al 2006]. Navajo neurohepatopathy, a disorder prevalent in the Native American Navajo population, has the manifestations of MPV17-related hepatocerebral mtDNA depletion syndrome as well as painless fractures, acral mutilation, and corneal anesthesia, ulceration, and scarring.

The clinical manifestations of MPV17-related hepatocerebral mtDNA depletion syndrome discussed here are based on the phenotype observed in those 31 individuals and summarized in Table 2.

Table 2. Clinical Manifestations of MPV17-Related Hepatocerebral mtDNA Depletion Syndrome

Clinical ManifestationsFrequency
Hepatic
 • Liver dysfunction
 • Liver failure
 • Hepatomegaly
 • Liver cirrhosis
 • Hepatocellular cancer
31/31 (100%)
31/31 (100%)
28/31 (90%)
14/29 (48%)
7/29 (24%)
2/31 (6%)
Neurologic
 • Developmental delay
 • Hypotonia, muscle weakness
 • White matter abnormalities in brain MRI 
 • Peripheral neuropathy
 • Seizures
 • Microcephaly
 • Ataxia
26/29 (90%)
24/29 (83%)
19/29 (66%)
10/29 (34%)
8/29 (28%)
3/29 (10%)
2/29 (7%)
2/29 (7%)
Failure to thrive26/29 (90%)
Metabolic
 • Lactic acidosis
 • Hypoglycemia
23/27 (85%)
20/27 (74%)
13/27 (48%)
Other manifestations
 • Renal tubulopathy
 • Gastroesophageal reflux
 • Vomiting and/or diarrhea
 • Corneal anesthesia and ulcers
 • Hypoparathyroidism

3/29 (10%)
3/29 (10%)
3/29 (10%)
3/29 (10%)
2/29 (7%)

Liver dysfunction. All reported individuals with MPV17-related hepatocerebral mtDNA depletion syndrome came to medical attention in infancy with manifestations of liver dysfunction including jaundice, cholestasis, elevated transaminases and gamma-glutamyl transpeptidase (GGT), hyperbilirubinemia, and coagulopathy. Approximately half were reported to have hepatomegaly.

In 90% of affected individuals liver disease progressed to liver failure typically during infancy or early childhood. About a quarter were reported to have liver cirrhosis typically in early childhood; two developed hepatocellular carcinoma at ages seven and 11 years [Karadimas et al 2006, El-Hattab et al 2010].

Liver biopsy may show cholestasis and cirrhosis.

Neurologic manifestations. The vast majority of affected individuals exhibited neurologic manifestations, including developmental delay (~85%), hypotonia and muscle weakness (~65%), and motor and sensory peripheral neuropathy (~30%). Very few affected individuals were reported to have normal psychomotor development; the majority was reported to have a variable degree of developmental delay. Some affected individuals presented with psychomotor delays during early infancy while others had normal development early in life followed by loss of motor and cognitive abilities later in infancy or early childhood. Peripheral neuropathy typically manifests in early childhood with muscle weakness and wasting, decreased reflexes, and loss of sensation in the hands and feet [Karadimas et al 2006, Wong et al 2007, Navarro-Sastre et al 2008, Spinazzola et al 2008, Kaji et al 2009, Parini et al 2009].

Less frequent neurologic manifestations include epilepsy, ataxia, dystonia, microcephaly, cerebrovascular infarction, and subdural hematoma.

Brain MRI abnormalities were reported in approximately one third of affected individuals, with white matter abnormalities (leukoencephalopathy) being the most common. Two individuals have been reported with T2 hyperintensities within the reticular formation of the lower dorsal brain stem and the reticulospinal tracts of the cervicomedullary junction [Merkle et al 2012].

Failure to thrive is one of the common manifestations, although some children have normal growth, especially early in the course of the disease.

Metabolic derangements occur in the vast majority with lactic acidosis occurring in approximately 75% and early-onset hypoglycemia in approximately 50%. Hypoglycemia typically presents during the first six months of life and can be associated with lethargy, apnea, and/or seizures. Lactic acidosis is a biochemical finding with mild to moderate elevation of lactate (3-9 mmol/L) [Karadimas et al 2006, Wong et al 2007, Navarro-Sastre et al 2008, Spinazzola et al 2008, Kaji et al 2009, Parini et al 2009].

Less frequent manifestations include renal tubulopathy, hypoparathyroidism, and gastrointestinal dysmotility manifest as gastroesophageal reflux, cyclic vomiting, and/or diarrhea.

Corneal anesthesia and ulcers were reported in three individuals considered to have Navajo neurohepatopathy who were homozygous for the mutation p.Arg50Gln.

Prognosis. Liver disease typically progresses to liver failure in affected children. Liver transplantation, the only treatment option for liver failure, has been performed in about one third of affected children. The outcome has not been satisfactory: half of the children undergoing transplantation died during the post-transplantation period because of multi-organ failure and/or sepsis.

Approximately half of affected children reported did not undergo liver transplantation and died because of progressive liver failure, the majority during infancy or early childhood. Three affected individuals homozygous for p.Arg50Gln died in their second decade.

Only four children were reported to survive without liver transplantation, the oldest of whom is age 13 years. Two of the four (including the 13-year old) are homozygous for the p.Arg50Gln mutation, indicating a better prognosis associated with p.Arg50Gln homozygosity (see Genotype-Phenotype Correlations; Table 3)

Two affected individuals developed hepatocellular carcinoma.

Table 3. Outcome of Children with MPV17-Related Hepatocerebral mtDNA Depletion Syndrome

Liver Transplant?OutcomeFrequency
No (21/31)DeathIn infancy or early childhood14/31 (45%)
In the second decade3/31 (10%)
Survival4/31 (13%)
Yes (10/31)Death5/31 (16%)
Survival5/31 (16%)

Genotype-Phenotype Correlations

To date, the p.Arg50Gln mutation has only been reported in the homozygous state in Navajo neurohepatopathy, which has the manifestations of MPV17-related hepatocerebral mtDNA depletion syndrome as well as corneal anesthesia, ulceration, and scarring.

In contrast to most MPV17 mutations that are associated with death in infancy or early childhood, the p.Arg50Gln mutation is associated with longer survival, suggesting that this is a hypomorphic mutation.

Homozygosity for p.Arg50Gln has been reported in ten children, five of whom died, typically in the second decade of life. Liver failure and death were reported in an infant homozygous for the p.Arg50Gln mutation whose mtDNA copy number in liver was very low (3%) [Spinazzola et al 2006], whereas children homozygous for the p.Arg50Gln mutation who survived longer have a relatively higher mtDNA copy number (10%-20%), suggesting that the degree of mtDNA depletion in the liver correlates with outcome in children homozygous for the p.Arg50Gln mutation [El-Hattab et al 2010].

The other MPV17 mutations have been associated with a lower mtDNA copy number than those associated with the p.Arg50Gln mutation and death in infancy or early childhood if not treated by liver transplantation [El-Hattab et al 2010].

Liver transplantation was performed in ten children, five of whom survived the post-transplant period. Of the five survivors, three are homozygous for p.Arg50Gln mutation, indicating a relatively better response to liver transplantation with this genotype [El-Hattab et al 2010].

Prevalence

The prevalence of MPV17-related hepatocerebral mtDNA depletion syndrome is unknown but likely to be very rare, with only 31 affected individuals being reported to date. Seven of the 31 are of Navajo ancestry.

Differential Diagnosis

See Mitochondrial DNA Depletion Syndrome: OMIM Phenotypic Series, a table of similar phenotypes that are genetically diverse.

Mitochondrial disorders are caused by defects in mitochondrial DNA (mtDNA) or nuclear genes involved in mitochondrial biogenesis and function. Defects in nuclear genes involved in the maintenance of mtDNA integrity can be associated with large-scale rearrangements of mtDNA (mtDNA multiple deletion syndromes) (see Mitochondrial DNA Deletion Syndromes) or with reduction in the mtDNA content (mtDNA depletion syndromes) (see Mitochondrial DNA Depletion Syndrome: OMIM Phenotypic Series).

Mitochondrial DNA depletion syndromes are phenotypically heterogeneous and may affect either a specific organ or a combination of organs, including muscle, liver, brain, and kidney. Clinically, mtDNA depletion syndromes are classified as:

  • Neurogastrointestinal encephalopathy associated with mutations in TYMP (encoding thymidine phosphorylase) or POLG (encoding DNA polymerase gamma);
  • Myopathy associated with mutations in TK2 (encoding thymidine kinase 2);
  • Encephalomyopathy associated with mutations in SUCLA2 (encoding ATP-dependent succinyl CoA synthase), SUCLG1 (encoding GTP-dependent succinyl CoA synthase), or RRM2B (encoding p53-induced ribonucleotide reductase B subunit);
  • Hepatocerebral form associated with mutations in C10orf2 (encoding Twinkle), POLG (encoding DNA polymerase gamma), DGUOK (encoding deoxyguanosine kinase), or MPV17.

MPV17-related hepatocerebral mtDNA depletion syndrome needs to be differentiated from other types of hepatocerebral mtDNA depletion syndromes associated with biallelic mutations in DGUOK, C10orf2, or POLG. In addition, mutations in BCS1L (encoding a mitochondrial protein involved in complex III assembly) and SCO1 (encoding a mitochondrial protein involved in complex IV assembly) have been associated with encephalopathy and hepatic dysfunction [Valnot et al 2000, Visapää et al 2002].

In MPV17-related hepatocerebral mtDNA depletion syndrome, liver involvement appears early in the course of the disease, unlike most of the other multisystem mitochondrial disorders with prominent neuromuscular involvement, in which liver complications are more commonly a late feature. In contrast to other mtDNA depletion syndromes, neurologic involvement in MPV17-related hepatocerebral mtDNA depletion syndrome is generally mild at the onset of disease [Wong et al 2007, El-Hattab et al 2010]. However, DGUOK-related hepatocerebral mtDNA depletion syndrome may also present as isolated liver disease without neuromuscular involvement [Freisinger et al 2006, Dimmock et al 2008].

Infantile liver failure is also a feature of the disorders caused by mutations in TRMU (encoding mitochondria tRNA-specific 2-thiouridylase 1) and GFM1 (encoding mitochondrial elongation factor G); mtDNA depletion is not a feature in these disorders [Coenen et al 2004, Zeharia et al 2009].

Note to clinicians: For a patient-specific ‘simultaneous consult’ related to this disorder, go to Image SimulConsult.jpg, an interactive diagnostic decision support software tool that provides differential diagnoses based on patient findings (registration or institutional access required).

Management

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs of an individual diagnosed with MPV17-related hepatocerebral mtDNA depletion syndrome, the following evaluations are recommended.

  • Hepatic
    • Liver function including liver transaminases (ALT and AST), GGT, albumin, total and direct bilirubin, and coagulation profile (PT and PTT)
    • Ultrasound examination to assess liver size and texture, and for the presence of masses
    • Alpha fetoprotein (AFP) to screen for hepatocellular carcinoma
    • Hepatology/liver transplantation consultation
  • Neurologic
    • Developmental evaluation
    • Neurologic consultation and comprehensive neurologic examination
    • Brain MRI to assess white matter and other abnormalities. The brain MRI findings can establish the degree of central nervous system involvement and serve as a baseline for monitoring the progression of the neurologic disease.
    • Nerve conduction velocity (NCV) to assess peripheral neuropathy. NCV can establish the degree of the peripheral nervous system involvement and serve as a baseline for monitoring the progression of the neurologic disease.
    • EEG if seizures are suspected
  • Nutritional evaluation
  • Plasma lactate and glucose concentration
  • Urinalysis and amino acids to assess for renal tubulopathy
  • Gastrointestinal consultation if gastrointestinal dysmotility is present
  • Ophthalmologic examination to assess corneal sensation and possible corneal ulcers/scaring
  • Medical genetics consultation

Treatment of Manifestations

Management should involve a multidisciplinary team including specialists in hepatology, neurology, nutrition, medical genetics, and child development. Treatment of MPV17-related hepatocerebral mtDNA depletion syndrome remains unsatisfactory with a mortality rate higher than 50% (see Clinical Description, Prognosis).

Nutritional support should be provided by a dietitian experienced in managing children with liver diseases.

Prevention of hypoglycemia requires frequent feeds and avoidance of fasting. Uncooked cornstarch (1-2 grams/kg/dose) can be used to manage hypoglycemia, and it may slow but not stop the progression of the liver disease [Spinazzola et al 2008, Parini et al 2009].

Liver transplantation. Although liver transplantation remains the only treatment option for liver failure, liver transplantation in mitochondrial hepatopathy is controversial, largely because of the multisystemic involvement. Liver transplantation has been performed in about one third of affected children; the outcome has not been satisfactory, with half of the transplanted children dying in the post-transplantation period because of multi-organ failure and/or sepsis (see Clinical Description, Prognosis).

Hepatocellular carcinoma. The two children reported with hepatocellular carcinoma (HCC) were treated by liver transplantation. Screening for HCC using periodic hepatic ultrasound examination and serum alpha fetoprotein concentration potentially could result in earlier diagnosis, enabling liver transplantation before metastasis or local invasion occurs.

Prevention of Secondary Complications

Nutritional deficiencies, for example of fat-soluble vitamins, can be prevented by ensuring adequate intake and frequent assessment by a dietitian experienced in managing children with liver diseases.

Surveillance

No clinical guidelines for surveillance are available.

The following evaluations are suggested, with frequency varying according to the severity of the condition:

  • Liver function tests including liver transaminases (ALT and AST), GGT, albumin, total and direct bilirubin, and coagulation profile (PT and PTT)
  • Hepatic ultrasound examination to screen for liver masses that might suggest HCC
  • Serum alpha fetoprotein (AFP) concentration
  • Developmental evaluation
  • Neurologic assessment
  • Nutritional assessment
  • Urinalysis and urine amino acids to assess for renal tubulopathy
  • Ophthalmologic examination

Agents/Circumstances to Avoid

Prolonged fasting can lead to hypoglycemia and should be avoided.

Evaluation of Relatives at Risk

See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.

Therapies Under Investigation

Search ClinicalTrials.gov for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Genetic Counseling

Genetic counseling is the process of providing individuals and families with information on the nature, inheritance, and implications of genetic disorders to help them make informed medical and personal decisions. The following section deals with genetic risk assessment and the use of family history and genetic testing to clarify genetic status for family members. This section is not meant to address all personal, cultural, or ethical issues that individuals may face or to substitute for consultation with a genetics professional. —ED.

Mode of Inheritance

MPV17-related hepatocerebral mtDNA depletion syndrome is inherited in an autosomal recessive manner.

Risk to Family Members

Parents of a proband

  • The parents of an affected child are obligate heterozygotes (i.e., carriers of one mutant allele).
  • Heterozygotes (carriers) are asymptomatic.

Sibs of a proband

  • At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
  • Once an at-risk sib is known to be unaffected, the risk of his/her being a carrier is 2/3.
  • Heterozygotes (carriers) are asymptomatic.

Offspring of a proband. To date no affected individuals have reproduced; therefore, fertility is not yet known.

Other family members. Each sib of the proband’s parents is at a 50% risk of being a carrier.

Carrier Detection

Carrier testing for at-risk family members is possible if the disease-causing mutations in the family have been identified.

Related Genetic Counseling Issues

Family planning

  • The optimal time for determination of genetic risk, clarification of carrier status, and discussion of the availability of prenatal testing is before pregnancy.
  • It is appropriate to offer genetic counseling (including discussion of potential risks to offspring and reproductive options) to young adults who are carriers or are at risk of being carriers.

DNA banking is the storage of DNA (typically extracted from white blood cells) for possible future use. Because it is likely that testing methodology and our understanding of genes, mutations, and diseases will improve in the future, consideration should be given to banking DNA of affected individuals.

Prenatal Testing

If the disease-causing mutations have been identified in the family, prenatal diagnosis for pregnancies at increased risk is possible by analysis of DNA extracted from fetal cells obtained by amniocentesis (usually performed at ~15-18 weeks’ gestation) or chorionic villus sampling (usually performed at ~10-12 weeks’ gestation).

Note: Gestational age is expressed as menstrual weeks calculated either from the first day of the last normal menstrual period or by ultrasound measurements.

Preimplantation genetic diagnosis (PGD) may be an option for some families in which the disease-causing mutations have been identified.

Resources

GeneReviews staff has selected the following disease-specific and/or umbrella support organizations and/or registries for the benefit of individuals with this disorder and their families. GeneReviews is not responsible for the information provided by other organizations. For information on selection criteria, click here.

  • American Liver Foundation
    75 Maiden Lane
    Suite 603
    New York NY 10038
    Phone: 800-465-4837 (Toll-free HelpLine); 212-668-1000
    Fax: 212-483-8179
    Email: info@liverfoundation.org
  • Canadian Liver Foundation (CLF)
    2235 Sheppard Avenue East
    Suite 1500
    Toronto Ontario M2J 5B5
    Canada
    Phone: 800-563-5483 (toll-free); 416-491-3353
    Fax: 416-491-4952
    Email: clf@liver.ca
  • Childhood Liver Disease Research and Education Network (ChiLDREN)
    The Children's Hospital, Section of Pediatric Gastroenterology/Hepatology/Nutrition
    13123 East 16th Avenue
    Suite B290
    Aurora CO 80045
    Phone: 720-777-2598
    Fax: 720-777-7351
    Email: hines.joan@tchden.org
  • Children's European Mitochondrial Disease Network
    Mayfield House
    30 Heber Walk
    Northwich CW9 5JB
    United Kingdom
    Phone: +44(0) 01606 43946 (Helpline)
    Email: info@cmdn.org.uk
  • Children's Liver Disease Foundation (CLDF)
    36 Great Charles Street
    Birmingham B3 3JY
    United Kingdom
    Phone: +44 (0) 121 212 3839
    Fax: +44 (0) 121 212 4300
    Email: info@childliverdisease.org
  • United Mitochondrial Disease Foundation (UMDF)
    8085 Saltsburg Road
    Suite 201
    Pittsburg PA 15239
    Phone: 888-317-8633 (toll-free); 412-793-8077
    Fax: 412-793-6477
    Email: info@umdf.org
  • Mitochondrial Disease Registry and Tissue Bank
    Massachusetts General Hospital
    185 Cambridge Street
    Simches Research Building 5-238
    Boston MA 02114
    Phone: 617-726-5718
    Fax: 617-724-9620
    Email: nslate@partners.org
  • RDCRN Patient Contact Registry: North American Mitochondrial Disease Consortium

Molecular Genetics

Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.

Table A. MPV17-Related Hepatocerebral Mitochondrial DNA Depletion Syndrome: Genes and Databases

Gene SymbolChromosomal LocusProtein NameLocus SpecificHGMD
MPV172p23​.3Protein Mpv17MPV17 homepage - Mendelian genesMPV17

Data are compiled from the following standard references: gene symbol from HGNC; chromosomal locus, locus name, critical region, complementation group from OMIM; protein name from UniProt. For a description of databases (Locus Specific, HGMD) to which links are provided, click here.

Table B. OMIM Entries for MPV17-Related Hepatocerebral Mitochondrial DNA Depletion Syndrome (View All in OMIM)

137960MPV17, MOUSE, HOMOLOG OF; MPV17
256810MITOCHONDRIAL DNA DEPLETION SYNDROME 6 (HEPATOCEREBRAL TYPE); MTDPS6

Normal allelic variants. MPV17 spans 13.6 kb and comprises eight exons.

Pathogenic allelic variants. To date, 20 different MPV17 mutations have been reported in children with hepatocerebral mtDNA depletion (Table 4). About half of those mutations are missense and the remaining half includes nonsense and splice site mutations and small deletions and insertions. A large deletion spanning exon 8 has also been reported.

Table 4. MPV17 Pathogenic Allelic Variants Discussed in This GeneReview

Type of MutationDNA Nucleotide ChangeProtein Amino Acid ChangeReference Sequences
Missensec.70G>Tp.Gly24TrpNM_002437​.4
NP_002428​.1
c.148C>Tp.Arg50Trp
c.149G>Ap.Arg50Gln
c.262A>Gp.Lys88Glu
c.280G>Cp.Gly94Arg
c.293C>Tp.Pro98Leu
c.485C>Ap.Ala162Asp
c.498C>Ap.Asn166Lys
c.509C>Tp.Ser170Phe
Nonsensec.206G>Ap.Trp69Ter
c.359G>Ap.Trp120Ter
In-frame deletionc.234_242del9p.Gly79_Thr81del
c.263_265del3p.Lys88del
c.271_273del3p.Leu91del
Frame shift deletionc.116-141del26p.Arg41ProfsTer63
Insertionc.22_23insCp.Gln8ProfsTer24
c.451_452insC p.Leu151ProfsTer39
Splicing sitec.70+5G>A
c.186+2T>C
Large deletion1.57-kb deletion spanning exon 8

Note on variant classification: Variants listed in the table have been provided by the author(s). GeneReviews staff have not independently verified the classification of variants.

Note on nomenclature: GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org). See Quick Reference for an explanation of nomenclature.

Normal gene product. MPV17 encodes the MPV17 protein, an inner mitochondrial membrane protein that is predicted to contain four transmembrane segments (pir.uniprot.org).

The function of the MPV17 protein and its role in the pathogenesis of mtDNA depletion syndrome are as yet unknown. It has been suggested that MPV17 plays a role in controlling mtDNA maintenance and oxidative phosphorylation activity in mammals and yeast [Karadimas et al 2006, Dallabona et al 2010].

Abnormal gene product. MPV17 mutations result in dysfunctional MPV17 protein resulting in impaired mtDNA maintenance leading to mtDNA depletion. Individuals with biallelic MPV17 mutations have a severe decrease in mtDNA content, leading to insufficient production of respiratory chain components, resulting in impaired energy production and organ dysfunction [Spinazzola et al 2006].

References

Medical Genetic Searches: A specialized PubMed search designed for clinicians that is located on the PubMed Clinical Queries page Image PubMed.jpg

Literature Cited

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Chapter Notes

Revision History

  • 17 May 2012 (me) Review posted live
  • 27 February 2012 (aeh) Original submission
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