Expressed in numerous tissues; not found in breast, heart, small intestine and liver . Isoform 1: Predominantly expressed in the testis (, ). Isoform 3: Predominantly expressed in the testis, at lower level in the placenta, during malignant progression of melanocytic tumors and in several tumors of varying origins (, ). Isoform 4: Predominantly expressed in the testis, at lower level in the placenta, during malignant progression of melanocytic tumors and in several tumors of varying origins (, ). Isoform 5: Predominantly expressed in the testis (, ). Isoform 6: Predominantly expressed in the testis (, ).