**4.1.2.3** *COCH* **gene and its protein**

The DFNA9 causative gene, *COCH* located on 14q12-q13, consists of 11exons and encodes a 550 amino acid extracellular matrix protein named cochlin. This protein has several domains including two von Willebrand factor A-like domains (vWFA1 and 2) and a LCCL domain (a region homologous to a domain in factor C of Limulus). To date, eleven missense mutations and one small deletion in *COCH* gene have been reported. Most of the missense mutations are located within exon 4 and 5 which encode the LCCL domain (Figure 2) [Robertson et al., 1998; Collin et al., 2006].

Fig. 2. Schematic structure of cochlin and distribution of the mutations along its domains. The NT signal peptide is followed by a LCCL domain and two vWF domains. S indicates several cysteine residues, NT denotes amino (NH2) terminus and CT denotes carboxyl (COOH) terminus.
