ONCOMODULIN IS ABUNDANT IN THE ORGAN OF CORTI

A small, acidic Ca2+-binding protein (CBP-15) was recently detected in extracts of the mammalian auditory receptor organ, the organ of Corti [Senarita et al. (1995) Hear. Res. 90, 169-175]. N-terminal sequence data for CBP-15 [Thalmann et al. (1995) Biochem. Biophys. Res. Commun. 215, 142-147] implied membership in the parvalbumin family and possib le identity with the mammalian P-parvalbumin oncomodulin. As shown her ein, the latter conclusion is supported by strong cross-reactivity bet ween CBP-15 and isoform-specific antibodies to oncomodulin. Moreover, we have succeeded in amplifying the guinea pig CBP-15 coding sequence from organ of Corti cDNA using degenerate oligonucleotide primers base d on the rat oncomodulin sequence. The deduced amino acid sequence of guinea pig CBP-15 displays 90%, 92%, and 98% identity with mouse, rat, and human oncomodulin isoforms. Demonstration of the presence of onco modulin in the organ of Corti is the first documentation of this subst ance in a postnatal mammalian tissue.