Zona Pellucida Domain-Containing Protein b-Tectorin is Crucial for Zebrafish Proper Inner Ear Development

Background: The zona pellucida (ZP) domain is part of many extracellular proteins with diverse functions from structural components to receptors. The mammalian b-tectorin is a protein of 336 amino acid residues containing a single ZP domain and a putative signal peptide at the N-terminus of the protein. It is 1 component of a gel-like structure called the tectorial membrane which is involved in transforming sound waves into neuronal signals and is important for normal auditory function. b-Tectorin is specifically expressed in the mammalian and avian inner ear. Methodology/Principal Findings: We identified and cloned the gene encoding zebrafish b-tectorin. Through whole-mount in situ hybridization, we demonstrated that b-tectorin messenger RNA was expressed in the otic placode and specialized sensory patch of the inner ear during zebrafish embryonic stages. Morpholino knockdown of zebrafish b-tectorin affected the position and number of otoliths in the ears of morphants. Finally, swimming behaviors of b-tectorin morphants were abnormal since the development of the inner ear was compromised. Conclusions/Significance: Our results reveal that zebrafish b-tectorin is specifically expressed in the zebrafish inner ear, and is important for regulating the development of the zebrafish inner ear. Lack of zebrafish b-tectorin caused severe defects in inner ear formation of otoliths and function