The protein encoded by this gene is a member of the serpin (serine proteinase inhibitor) superfamily, and ovalbumin(ov)-serpin subfamily. It was originally discovered as a placental thrombin inhibitor. The mouse homolog was found to be expressed in the hair cells of the inner ear. Mutations in this gene are associated with nonsyndromic progressive hearing loss, suggesting that this serpin plays an important role in the inner ear in the protection against leakage of lysosomal content during stress, and that loss of this protection results in cell death and sensorineural hearing loss. Alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Sep 2010].