Morphologically abnormal bovine sperm: A model for the study of spermatogenesis, sperm function and sperm contributions to preimplantation embryo development

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The global demand for animal proteins will substantially increase over the next 20-25 years. Therefore, improving the efficiency of food animal productivity is crucial. Fertility of bulls, or their frozen semen, is a major determinant of cattle production. Changes in the structure and function of sperm at the submicroscopical level (not detectable during routine semen evaluation) influence bull fertility. Increasing knowledge regarding the molecular basis of sperm development (spermatogenesis) and sperm function will have implications for improving fertility predictions in cattle. This proposal is based on the general hypothesis that comparison of morphologically normal versus grossly abnormal sperm (with distinct functional impairments) obtained from the same bull will be a suitable approach for accomplishing this goal. Any disruption in testicular thermoregulation induces abnormal sperm production. Based on this principle, we recently used scrotal insulation to impair sperm production in bulls, and we recovered normal (pre-insulation) versus abnormal sperm from the same bull (a unique advantage of this model compared to the use of laboratory animals). In preliminary studies using these sperm, we identified a novel molecule (testis-specific isoform of Na+/K+ATPase) involved in the regulation of sperm function, clearly demonstrating the potential of this model for creating new knowledge in gamete biology. The current proposal is a continuation of this study and is focused on investigating the molecular basis of the development and impaired function of pyriform sperm (pear-shaped sperm; the most common sperm abnormality in infertile bulls). I expect that this study will increase knowledge regarding spermatogenesis, regulation of sperm function and sperm contributions to early embryo development, which is the long-term goal of my research. At the applied level, this study may identify molecular markers of fertility, with important implications for improving animal productivity and understanding male-factor infertility at an interdisciplinary level. Moreover, this research program will train highly qualified individuals for academia and industry.