Expression of POTE protein in human testis detected by novel monoclonal antibodies

The POTE gene family is composed of 13 highly homologous paralogs preferentially expressed in prostate, ovary, testis, and placenta. We produced 10 monoclonal antibodies (MAbs) against three representative POTE paralogs: POTE-21, POTE-2γC, and POTE-22. One reacted with all three paralogs, six MAbs reacted with POTE-2γC and POTE-22, and three MAbs were specific to POTE-21. Epitopes of all 10 MAbs were located in the cysteine-rich repeats (CRRs) motifs located at the N-terminus of each POTE paralog. Testing the reactivity of each MAb with 12 different CRRs revealed slight differences among the antigenic determinants, which accounts for differences in cross-reactivity. Using MAbs HP8 and PG5 we were able to detect a POTE-actin fusion protein in human testis by immunoprecipitation followed by Western blotting. By immunohistochemistry we demonstrated that the POTE protein is expressed in primary spermatocytes, implying a role in spermatogenesis.