H3f3b knockout ( KO) mouse embryonic fibroblasts (MEFs) exhibit chromosomal bridges, severe karyotypic abnormalities, and ectopic staining of CENP-A and CREST. (A) Karyotyping revealed a number of types of abnormalities in H3f3b KO MEFs not observed in wildtype (WT) MEFs including endoreduplication, chromosomal fragmentation, and tri-radial chromosomes (See also Additional file 3: Figure S3 and Table 1). (B) Staining of WT 63 and KO 56 cells with CREST and CENP-A antisera (green and red in merge, respectively). (C) KO MEFs with chromosomal bridges had higher levels of CREST and CENPA foci (white arrows). (D) Quantification of foci staining for KO 49 and 52 versus WT 46 and 48. An average of 17 confocal sections per nuclei were analyzed using ImageJ software as in this study . Scale bars = 10 um.