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In this study, we aimed at analysing the expression of the PRY (PTPN-13 like on the Y chromosome) gene, located on the Y chromosome, in order to define the function of this gene. Active copies of the PRY gene (PRY1 and PRY2) are located in the AZFb region. PCR amplification of PRY cDNA indicated that the PRY gene is expressed in testicular tissue and ejaculated sperm, but not in Percoll-treated sperm. Furthermore, immunocytochemistry on testicular tissue showed the expression of the PRY gene in a small number of spermatozoa and spermatids. In the ejaculate of the male partner of 18 infertile couples, the PRY protein was found in 1.5-51.2% of spermatozoa and in most of the sperm precursor cells. The percentage of spermatozoa showing DNA fragmentation was also determined in 13 of these samples, by using the TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labelling (TUNEL) reaction. These data correlated with the percentage of PRY-positive cells. When double labelling for PRY and DNA fragmentation was performed to assess whether PRY-positive cells also show DNA fragmentation, we saw that 27-48% of the PRY-positive spermatozoa were also positive for the TUNEL reaction. The overall data of RNA analysis, immunocytochemistry and the TUNEL reaction indicate that the role of the PRY gene in spermatogenesis can be questioned, but suggest its involvement in apoptosis of spermatids and spermatozoa.