Ubiquitin as an Objective Marker of Semen Quality and Fertility in Bulls

Andrology is one of few fields of medicine and biology in which biochemical and molecular tools are not routinely used for evaluation and diagnostics (discussed by Eliasson, 2003). Accurate evaluation of an infertile male is of paramount importance for proper diagnosis of couples in human infertility, but also for an accurate estimation of current fertility and prediction of future fertility in large farm animals including bulls, boars, and stallions. This is currently not possible due to the paucity of a universal, objective semen assay capable of detecting a wide array of both visible and cryptic sperm abnormalities (Amann, 1989; Nikoletos et al., 1999). It is indisputable the currently available, subjective, and automated methods of semen evaluation provide important information about the quality of a semen sample. However, each method has major shortcomings that may result in a large portion of defective spermatozoa being missed by even a well-trained semen evaluator. These shortcomings are mostly due to the fact current semen evaluation techniques are either subjective and/or detect only certain types of sperm abnormalities found in fertile and infertile males. It is thus highly desirable to develop new, objective, unbiased semen quality assays that would reflect both current and future fertility of a male. Toward this goal, we have been working on the identification of “negative” sperm quality markers, i.e. proteins associated with morphologically and/or functionally defective spermatozoa in male farm animals and humans. The following presentation will discuss the identification of sperm protein ubiquitin as one such fertility marker.