(A) Dppa2 inhibits sperm aster microtubule assembly. Demembranated sperm nuclei were added together with calcium to metaphase extracts supplemented with rhodamine-labeled tubulin (red). Samples were fixed and stained with Hoechst 33342 (blue).
(B) Quantification of tubulin fluorescence intensity from (A). Data shown indicate mean and standard error from > 30 asters per sample and are representative of 3 independent experiments.
(C) Dppa2 inhibits spindle assembly in a dose-dependent manner. Metaphase spindles were assembled in extracts supplemented with MBP-Dppa2 fusion proteins and rhodamine-labeled tubulin.
(D) Quantification of spindle length from (C). Data shown are mean and standard deviation from 30 spindles per sample.
(E) Chromatin-independent microtubule assembly in Xenopus egg extracts. Recombinant GST-Dppa2 protein was added to metaphase extracts together with 0.5 % DMSO. Polymerized microtubules were recovered by pelleting and analyzed by Coomassie staining.
(F) Dppa2 inhibits microtubule polymerization in vitro. MBP-Dppa2 was added to purified bovine tubulin together with 0.5 % DMSO. Polymerized microtubules were recovered by pelleting and analyzed by Coomassie staining.
Scale bars, 10 μm.
See also Figure S3.