Adenosine diphosphate-ribosylation factor 1 controls spindle assembly during first meiotic division in bovine oocytes

Adenosine diphosphate-ribosylation factor 1 (ARF1) is a member of guanosine triphosphate (GTP)binding proteins family associated with Golgi complexes. ARF1 regulated asymmetric cell division in female meiosis in mouse. However, little is known about its function in bovine oocyte meiosis. In the present study, we examined the localization, expression and functions of ARF1 during bovine oocyte meiotic maturation. Active form ARF1 Q71L -Venus showed that ARF1 co-localized with α-tubulin on the spindle from the M I to the M II stage. Inhibition of ARF1 activity by microinjecting mRNA of a dominant negative mutant form of ARF1 (ARF1 T31N ) or ARF1 morpholino (ARF1 MO) into the germinal vesicle (GV) oocytes, and treating GV oocytes with brefeldin A (BFA), an inhibitor of Golgi-based membrane fusion led to abnormal spindle assembly and cytokinesis failure. On the contrary, microinjection of mRNA of a positive mutant form of ARF1 (ARF1 Q71L ) into GV oocytes had no effect on spindle assembly and the oocytes could undergo normal cytokinesis to generate one large egg with one small polar body. From the above, our results suggest that ARF1 plays an essential role in spindle assembly in bovine oocytes.