Endogenous retrovirus sequences expressed in male mammalian reproductive tissues: a review.

Objectives: To review the research findings on the expression of endogenous retroviruses and retroviral-related particles in male mammalian reproductive tissues, and to discuss their possible role in normal cellular events and association with disease conditions in male reproductive tissues.

Data Sources: Published findings on endogenous retrovirus (ERV) expression in vertebrate reproductive tissues.

Study Selection: Relevant citations on ERVs and male reproduction by research groups worldwide.

Data Extraction: Literature search on Medline and Pubmed upto the year 2000, and retrieval of relevant articles cited from international and local journals.

Data Synthesis: Most of the studies demonstrated integrated retroviruses and retroviral-related sequences in human and mouse testis, epididymis and vas deferens. Endogenous retroviruses in human and mice may be associated with normal cellular differentiation and development, and carcinogenesis. In humans, one ERV family, human endogenous retrovirus-K (HERV-K) is abundantly expressed, and is associated with germ cell tumours, while ERV3 env is expressed in normal human testis.

Conclusion: The expression of ERVs in male reproductive tissues suggests a possible role in normal and disease conditions involving the testis and epididymis. These speculative functions may include among others spermatogenesis and or sperm maturation or tumour formation. However, further studies need to be carried out to investigate specific roles of ERVs in male reproductive events.