Preferred Minimum: 8 mL whole blood Absolute Minimum: 4 mL whole blood

DFNA8/12 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 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, 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. Sensitivity is greater than 98%.