Fig. 1. IP₃R1 is differentially phosphorylated in mouse oocytes, eggs and zygotes. (A) Immunoblots (IB) of oocyte lysates during different stages of oocyte maturation (GV, GVBD, MI and IVM/MII) were probed with the MPM2 antibody (upper panel) and, after stripping of the blot, with the IP₃R1 antibody (lower panel). Quantification of IP₃R1 MPM2 reactivity is shown in the graph below the IB panels. Data are presented as means±s.e.m., both here and throughout the manuscript. Fifty mouse oocytes were used per lane, both here and elsewhere in the study. (B) Kinase activity assays performed on lysates from five oocytes collected simultaneously with oocytes for western blotting; H1 and MBP phosphorylation indicate MPF and MAPK activity, respectively. The graph below shows quantification of kinase activities. Bars with an asterisk are significantly different from those without a symbol within kinase here and elsewhere. The presence of two vertical lines indicates that lanes were cut and pasted from the same blot/exposure during the preparation of the figure here and elsewhere in the manuscript. (C) Lysates from MII eggs and zygotes collected at 2PB, PN and Mit I were probed with MPM2 antibody (upper panel) and re-probed with IP₃R1 antibody (lower panel), as described above. (D) Kinase activity assays performed at the same cell-cycle stages as for C. Bars with asterisks are significantly different from those without a symbol.