Major protein of the otoconia, a calcium carbonate structure in the saccule and utricle of the ear (PubMed:17300776). Together with OTOL1, acts as a scaffold for otoconia biomineralization: sequesters calcium and forms interconnecting fibrils between otoconia that are incorporated into the calcium crystal structure (PubMed:21655225, PubMed:24748133). Together with OTOL1, modulates calcite crystal morphology and growth kinetics (PubMed:24748133). It is unlikely that this protein has phospholipase A2 activity (PubMed:17300776). Interacts with OTOL1. In the embryo, highly expressed in the developing otocyst with weak expression in the brain. Also expressed in nonsensory epithelia of both the vestibular and cochlear portions of the developing inner ear. Not expressed in adult or embryonic macular sensory epithelia. Expressed from embryonic day 9.5. Consists of 3 PA2-type domains. Otoconia show a strongly reduced matrix-calcium. Belongs to the phospholipase A2 family.