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.
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.
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
Oligonucleotide primers have been designed for amplification of each exon including intron/exon boundaries of
TECTA. These amplimers are used for bi-directional sequencing.
Sensitivity is greater than 98%.
Turn around time is approximately 3 months
(Average TAT - 48 days).
Indications for screening
Screening should be considered in persons with
nonsyndromic, mid-frequency hearing loss. Example audiogram:
GeneReviews – Deafness and Hereditary Hearing Loss Overview
Verhoeven, K., et al. A
gene for autosomal dominant nonsyndromic hearing loss (DFNA12)
maps to chromosome 11q22-24. Am.
J. Hum. Genet. 60:
PubMed ID: 9150164
Van Camp, G., et al. Nonsyndromic
hearing impairment: unparalleled heterogeneity. Am.
J. Hum. Genet. 60:
PubMed ID: 9106521
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:
PubMed ID: 9949200
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