Instead, the multi-C2 domain protein otoferlin, whose encoding gene OTOF is responsible for human recessive deafness DFNB9, expresses in IHCs in close correlation with afferent synaptogenesis and plays a central role in Ca2+-triggered synaptic exocytosis (Roux et al., 2006). This evidence concerns the gene OTOF and autosomal recessive nonsyndromic hearing loss 9.