MTTL1
The Clinical Diagnostics Service of the Molecular Otolaryngology & Renal Research Laboratories is a Joint Commission-approved CLIA-accredited diagnostic laboratory that offers mutation screening of several genes.

MTTL1 (OMIM# 590050)
The A3243G mutation in the MTTL1 gene (OMIM# 590050), which encodes the mitochondrial transfer RNA for leucine, has been shown to segregate with maternally inherited diabetes mellitus, sensorineural deafness, hypertrophic cardiomyopathy and/or renal failure (Manouvrier et al., 1995.) The A3243G mutation also causes MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) (OMIM# 540000). MORL offers screening for this mutation.

MORL screening methodology
Samples are amplified with an oligonucleotide primer pair that flanks the  A3243G mutation within the MTTL1 gene, followed by sequencing.

Sensitivity
Sensitivity is greater than 99%.

Turn-around time
Turn around time is approximately 3 months (Average TAT - 22 days).

Indications for screening
This test is appropriate for a patient suspected of having maternally inherited diabetes mellitus and sensorineural hearing loss.

GeneTests  GeneReviews – Nonsyndromic Hearing Loss, Mitochondrial

References
Majamaa, K. et al.: Epidemiology of A3243G, the Mutation for Mitochondrial Encephalomyopathy, Lactic Acidosis, and Strokelike Episodes: Prevalence of the Mutation in an Adult Population. Am. J. Hum. Genet. 63:447-454, 1998.
PubMed ID:  9683591 
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Manouvrier, S et al; Point mutation of the mitochondrial tRNA(leu) gene (A 3243 G) in maternally inherited hypertrophic cardiomyopathy, diabetes mellitus, renal failure, and sensorineural deafness. J. Med. Genet. 32: 654-656, 1995.
PubMed ID: 7473662
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