Understanding mechanisms of human fertilization

1. Role of the human sperm centrosome: Utilizing fluorescent antibodies, we are labeling the centrosome in human spermatozoa. In order to assess the importance of the sperm integrity during fertilization, we dissect the spermatozoa and label the different sperm segments (head and tail) to determine the location of the centrosome. As an additional step, we perform the injection of sperm segments into human oocytes and assess its ability to fertilize and form embryos. To investigate the genetic normality of those embryos, we analyze them by fluorescence in situ hybridization (FISH).

2. FISH on human sperm and spermatids: We are conducting a study to assess whether there is a correlation between male infertility and genetic status of the spermatozoa. For that purpose, we are analyzing human spermatozoa by multiprobe FISH analysis and determining the incidence of aneuploidy and ployploidy.

3. Sperm cytosolic factor isolation: We have developed a technique to isolate a cytosolic fraction present in the human spermatozoa, able to activate mammalian oocytes. We have injected this factor in immature mouse and human oocytes and we have observed the calcium oscillations triggered by this factor. We have observed a pattern of oscillations similar to that occurring during normal fertilization. In addition, we have tested this factor in human unfertilized oocytes injected with spermatozoa or with round spermatids, and observed a very high rate of oocyte activation and embryo development. We are in the process of isolating the specific protein responsible for oocyte activation.