Figure 6. Disruption of cortical granule translocation severely impairs the zona pellucida block to polyspermy.

(a) Maximum intensity Z projections of in vitro fertilized oocytes from Rab27a^+/Ash (control) or Rab27a^Ash/Ash (mutant) oocytes, fixed and stained with Hoechst. Male and female pronuclei and polar body (PB) are indicated. Note the extra sperm heads present inside the zona pellucida in mutant oocytes (arrows). Scale bar, 20 μm. (b) Quantification of the number of fertilized oocytes which had extra sperm heads in the perivitelline space in Rab27a^+/Ash or Rab27a^Ash/Ash oocytes (mean±s.d.; Student's t test) (c) Quantification of the number of extra sperm inside the perivitelline space of fertilized Rab27a^+/Ash or Rab27a^Ash/Ash oocytes. (d) Quantification of remaining cortical granules in the centre of Rab27a^+/Ash or Rab27a^Ash/Ash oocytes after fertilization (mean±s.d.; Student's t test). (e) Mechanistic model of the two cortical granule translocation mechanisms in mammalian oocytes. See text for details. Significance levels: ***P<0.001, from three experiments.