MITOCHONDRIAL HEARING LOSS - MUTATION mt A1555G
Gene Symbol: MT-RNR1 (12S rRNA)
TURNAROUND TIME: 8 business days
TESTING METHODOLOGY: Detection of the mt.1555A>G mutation by PCR and restriction enzyme digestion.
- Collect: Prefer two 5ml whole blood EDTA (lavender top) tube.
- Min. Collection: 0.7 ml whole blood EDTA.
- Transport: blood EDTA at Room Temp shipped regular next day air (No Saturday delivery; store specimen at 40°C and ship Monday).
- Stability: Ambient: up to 7 days; Refrigerated: 2 weeks. Frozen: unacceptable
- Unacceptable Conditions: Serum. Frozen or severely hemolyzed blood. Clotted blood.
- Prenatal testing: Direct: 5ml direct unspun amniotic fluid or 15mg CVS tissue with a backup flask growing. Culture: confluent T25 flask. Maternal blood sample is required for maternal cell contamination studies.
A Molecular Genetics Laboratory Test Requisition must accompany the specimen. Contact the Molecular Laboratory at 918-502-1721 to obtain further information.
Counseling and informed consent are recommended for genetic testing; Center for Genetic Testing at Saint Francis consent form
is available as a resource but not required.
Incidence: Not well known and varies by ethnicity. May represent a small percentage of individuals with Non-Syndromic Hearing Loss (NSHL) that show no signs of Connexin 26 defects.
Disease Characteristics: Moderate to profound late onset, or aminoglycoside induced NSHL
Molecular Genetic Mechanism: The mt.1555A>G mutation in the mitochondrial genome has been associated with predisposition to aminoglycoside ototoxicity and/or late-onset sensorineural hearing loss. Roughly 70% of cases of mitochondrial hearing loss are due to mutations in the MT-RNR1 gene.
Clinical Sensitivity: 70%
Analytical Sensitivity: 99%
Test Limitations: mutations present in less than 30% of the mitochondrial genomes may not be detected.
INDICATIONS FOR USE:
- Moderate to profound hearing loss
- Family history of hearing loss suggestive of maternal inheritance
- Hearing loss following known aminoglycoside exposure
- Known familial mutation
- Relatives of an affected individual that may be at risk for aminoglycoside ototoxicity.
OMIM MT-RNR1 - www.omim.org/entry/561000
OMIM Aminoglycoside-Induced Deafness - www.omim.org/entry/580000
Genetics Home Reference: www.ghr.nlm.nih.gov/gene/MT-RNR1
Gene Reviews: www.ncbi.nlm.nih.gov/books/NBK1422