An intact acrosome is required for the chemotactic response to progesterone in mouse spermatozoa

GUIDOBALDI, HA; HIROHASHI N; CUBILLA, MC; BUFFONE, MG; GIOJALAS, LC

MOLECULAR REPRODUCTION AND DEVELOPMENT

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2017

1040-452X

Mammalian sperm cells become competent to fertilization in the oviduct, a process known as capacitation. This involves the acquisition of not only exocytotic competence of the acrosome but also chemotactic responses, mechanisms that contribute to the success of fertilization. Chemotaxis leads to orientation of spermatozoa to localize the egg position, whereas the acrosome reaction facilitates sperm binding and fusion with the oocyte membrane. Mammalian spermatozoa are able to sense picomolar concentrations of progesterone that drive chemotactic behavior, however the state of the acrosome in the chemotactic sperm is unknown. To elucidate the acrosomal integrity of sperm responding to progesterone-induced chemotaxis, genetically modified mouse spermatozoa that allow us to evaluate the acrosomal status while swimming were employed in a chemotaxis assay under fluorescence microscopy. We first showed that wild type mouse spermatozoa could chemotactically respond to a gradient of progesterone. Then, we verified that the genetic modifications performed in the mouse did not affect sperm chemotaxis to progesterone. Next, we found that acrosome-intact, but not reacted spermatozoa were chemotactically orientated to picomolar concentrations of progesterone. Normally chemotaxis occurs prior to the acrosome reaction. Indeed, our results suggest that premature commitment of the acrosome exocytosis will cause navigation failure; therefore, a proper control of the acrosome reaction is required for fertilization success and malefertility.