CYTOCHROME b (MTCYB)

 

DESCRIPTION - Mitochondrial DNA Analysis

Mutations of the mitochondrially encoded human cytochrome b gene (MTCYB) are almost exclusively associated with isolated complex III deficiency in muscle. Cytochrome b is essential for assembly and function of complex III. Cytochrome b is the only protein subunit of complex III (ubiquinol-cytochrome c oxidoreductase). Complex III is a hydrophobic integral membrane protein with eight transmembrane helices and contains 11 polypeptides. In many patients the mutation appears to arise sporadically and is restricted to muscle tissue. This most often affects young adults who display skeletal muscle weakness and exercise intolerance, and may also exhibit myoglobinuria and mitochondrial proliferation as evidenced by the presence of ragged-red fibers (RRF) on muscle biopsy. Children with cytochrome b mutations have been reported and display mitochondrial encephalopathy, cardiomyopathy, septo-optic dysplasia, and multisystem disorders.

Test Order Code CYTB
CPT Codes

83891 x 1, 83898 x 4, 83904 x 8
Indications For Testing
  • Confirm diagnosis of affected individuals with;
  • Multi-systemic disorders involving neuromuscular, neurosensory, CNS, cardiac, renal, hepatic, GI, immune, endocrine systems, etc.
  • Family history of mitochondrial disorders
  • Matrilineal family members with known mitochondrial DNA mutations and asymptomatic carrier testing
  • Confirmation of mitochondrial mutations
Turn Around Time Less than two weeks. Expedited analysis is available upon request for an additional charge.
Specimen Requirements Ship one of the following:

Saliva
You must order either the DNA Specimen Collection Kit – Sponge Swab (Part Number 443006) or the DNA Specimen Collection Kit – Saliva Tube (Part Number 443007) from Transgenomic to send a saliva sample. Follow the directions in the kit for specific saliva collection requirements.

Peripheral Blood
A full 4 ml blood sample in the 4 ml Lavender-top (EDTA) tube provided in the DNA Specimen Collection Kit (Part Number 443002) is required. Keep the sample at ambient temperature and ship by overnight courier to the test laboratory.

Muscle Biopsy
Tissue can be fresh or frozen, and must be shipped on dry ice.

  • Adults: 40-50 mg
  • Children: 25 mg
Specimen Kits DNA Specimen Collection Kits can be obtained from Transgenomic Labs.
Shipping and Contact Information Transgenomic Labs
Five Science Park, New Haven, CT 06511 USA
Phone:1.877.274.9432 Fax: 203.786.3418
E-mail: labservice@transgenomiclabs.com
Test Submission and Patient Consent Forms  Test Requisition and Patient Consent Form

Due to the unique nature of genetic testing, patients should receive pre-test and post-test counseling. Informed consent is recommended.

Test Methodology Genomic DNA is amplified by PCR for the specification region of interest and sequenced for confirmation.

Additional References

Mitomap
A human mitochondrial genome database.  http://www.mitomap.org/

Note: The performance characteristics of this test were validated by Transgenomic Labs. The U.S. Food and Drug Administration (FDA) has not approved this test. However, FDA approval is currently not required for clinical use of this test. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. Transgenomic Labs is authorized under Clinical Laboratory Improvement Amendments (CLIA) to perform high-complexity testing.