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

DFNA8/12 (OMIM#: 601543)
Linkage studies identified a region on chromosome 11q22-24 as the site of a deafness-causing gene in families segregating pre-lingual autosomal dominant nonsyndromic hearing loss that is most severe in the mid-frequencies. Audiograms displaying this type of hearing loss may be referred to as “cookie-bite” audiograms. TECTA has been identified as the causally-related gene at this locus.

DFNB21 (OMIM#: 603629) 
Mustapha and colleagues studied a Lebanese family with pre-lingual, severe-to-profound autosomal recessive nonsyndromic hearing loss mapping to chromosome 11q23-q25 (Mustapha et al., 1999). A splice donor mutation in TECTA was found to segregate with the hearing loss in this family.

TECTA
The gene, TECTA (OMIM# 602574), contains 23 exons and encodes the 2155 amino acid protein TECTA (Alpha Tectorin).  Alpha Tectorin is the major non-collagenous component of the tectorial membrane.  In humans, mutations in TECTA cause both autosomal dominant and autosomal recessive nonsyndromic hearing loss. Over 20 mutations have been identified in TECTA including missense, nonsense, and splice site mutations.

MORL screening methodology
Screening for TECTA is performed via DHPLC and sequencing.  Oligonucleotide primers have been designed to amplify each exon.  Amplified samples are run on the DHPLC; abnormal elution profiles are sequenced to determine the specific mutation.

DHPLC profile of EYA1, Exon 8

Legend: Profiles in brown and black contain mutations; profile in purple is wild type.

Sensitivity
Sensitivity is greater than 98%.

Turn-around time
Turn around time is approximately 3 months.

Cost: $500

Indications for screening
Screening should be considered in persons with nonsyndromic, mid-frequency hearing loss.  Example audiogram:

 GeneTests  GeneReviews – Deafness and Hereditary Hearing Loss Overview

References
Verhoeven, K., et al.  A gene for autosomal dominant nonsyndromic hearing loss (DFNA12) maps to chromosome 11q22-24. Am. J. Hum. Genet. 60: 1168-1173, 19972.
PubMed ID: 9150164 
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Van Camp, G., et al.  Nonsyndromic hearing impairment: unparalleled heterogeneity. Am. J. Hum. Genet. 60: 758-764, 1997.
PubMed ID: 9106521
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Mustapha, M., et al.  An alpha-tectorin gene defect causes a newly identified autosomal recessive form of sensorineural pre-lingual non-syndromic deafness, DFNB21. Hum. Molec. Genet. 8: 409-412, 1999.
PubMed ID: 9949200
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Meyer, N. et al.  Identification of three novel TECTA mutations in Iranian families with autosomal recessive non-syndromic hearing impairment.  Am. J. Med. Genet. 143:1623-9, 2007.
PubMed ID: 17431902
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