Fig. 7. Nucleoporins and vimentin are required for pronuclear migration and apposition. (A) Pronuclear apposition is normal when control IgG antibodies are transfected into bovine zygotes, but female pronuclear migration is inhibited following transfection of antibodies against either nuclear pore complex proteins (NPCs) or vimentin. NPCs show normal distribution around the female (F) and the male (M) pronucleus in controls (left), and similar localization is seen following anti-nucleoporin antibody transfection (center). Vimentin branching around and between the distant pronuclei is detected after anti-vimentin antibody transfection (right). Dynactin p150^Glued shows normal localization to pronuclei in control IgG-transfected and anti-nucleoporin-transfected zygotes, but its distribution around pronuclear surfaces appears reduced following transfection with anti-vimentin antibodies. Scale bar, 10 µm. (B) Quantification of the effects of antibody transfection on pronuclear apposition. Zygotes were transfected 12 hours post-insemination (HPI) and developed until 24 HPI, when they were then fixed and analysed by immunocytochemistry. Pronuclear apposition was scored by measuring the distance between pronuclei, with 10 µm representing the average diameter of a pronucleus. Pre-absorbed antibodies refer to anti-nucleoporin and anti-vimentin antibodies incubated with their antigens prior to transfection.