Figure 1.

Emi2 expression is tissue specific and declines after oocyte activation, and its relationship to Emi1. (A) Alignment of mouse Emi1 and Emi2 predicted amino-acid sequences showing conserved domains. Identities are indicated in red. Mm, Mus musculus. (B) Phylogenetic tree of Emi1 and Emi2 orthologs. Numbers indicate bootstrap support from neighbour jointing. Xl, Xenopus laevis; Mm, Mus musculus; Hs, Homo sapiens. RT–PCR for mouse Emi1, Emi2 and β-actin transcripts in different tissues (C) and in gametes and preimplantation embryonic development (D), showing 0.75–3.3 cell equivalents per lane. β-Actin served as an internal control. GV, germinal vesicle; GVBD, GV breakdown. (E) Immunoblotting of recombinant Emi2-Myc-His (left in each panel) and Emi1-Myc-His to show mutual specificity of anti-Emi1 and -Emi2 polyclonal antibodies. (F) Tissue immunoblotting showing levels of Emi2 protein in brain (Br), heart (H), lung (Lu), liver (Li), spleen (Spl), kidney (K), skeletal muscle (SM), testis (T) and ovary (Ov); 30 μg total protein were loaded per lane. Immunoblotting showing levels of Emi1 and Emi2 in oocytes and at different preimplantation developmental stages derived by (G) natural mating, or (H) of Emi2 in a developmental time course for SrCl₂-induced parthenogenotes. The gels of (G) and (H) were, respectively, loaded with 30 or 60 oocytes or embryos per lane.