d to be overexpressed in a variety of human cancer cell lines and ectopic overexpression of Aurora-C can also induce cell transformation and tumor formation. However, its expression in tumor cells and normal somatic tissues is still the matter of some debate. AuroraB is a member of the chromosomal passenger complex, which localizes to the centromeres/kinetochores from prophase to metaphase and to the central spindle and midbody during cytokinesis. In contrast, endogenous Aurora-C protein has never been detected in normal somatic cells by immunofluorescence or Western blot analyses using fully validated antibodies. Instead, ectopically expressed tagged Aurora-C has been detected in transfected cells, where it showed a localization pattern similar to 
that of Aurora-B. The role of Aurora-B in meiotic chromosome orientation during meiosis has recently been reviewed by Watanabe. In this review, we will focus on the possible role of Aurora-C during male and female meiotic divisions. Aurora-C in Mouse Spermatocytes: Subcellular Localization, Transcriptional Regulation, and Functional Implications The subcellular localization of endogenous Aurora-C during male meiotic division had been carefully examined by confocal immunofluorescence microscopy in mouse spermatocytes. In germ cells, the meiotic prophase consists of five sequential stages: leptotene, zygotene, pachytene, diplotene, and diakinesis. AuroraC was first detected at the order BioPQQ centromeric regions in early diplotene spermatocytes, after which it was found to spread along the chromosomal arms of sister chromatids during diakinesis. Upon the transition from diakinesis to MI, Aurora-C gradually dissociates from the chromosome arms and becomes concentrated at the centromeres near the kinetochores. Thereafter, it relocalizes to the spindle midzone and midbody during the anaphase I/telophase I and anaphase II/telophase II transitions, respectively . A similar localization pattern was reported for AuroraB in mouse spermatocytes. However, while Aurora-B was detected in mitotic spermatogonia, Aurora-C was not, suggesting that Aurora-C may play a unique role in male meiotic division. The finding that Aurora-C PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19816210 and -B co-localize during male meiotic divisions raised several interesting questions: how are Aurora-C/-B recruited to the appropriate positions to execute their meiotic functions during spermatogenesis Do Aurora-C/-B play similar or different roles during male meiotic divisions Since Aurora-C is mainly restricted in germ cells, how is Aurora-C regulated during spermatogenesis In somatic cells, Aurora-B is a member of the CPC along with several non-enzymatic subunits, including INCENP, survivin, and Borealin; together, the members of this complex contribute to regulation of chromosome segregation, microtubulekinetochore attachments, and cytokinesis. INCENP contains a conserved C-terminal IN-box that binds Aurora-B and an Nterminal region that targets to centromeres. Interestingly, INCENP can be detected in meiotic cells prior to the appearances of Aurora-B and -C. It is first found at the central element of the synaptonemal complex, from the zygotene to late pachytene stages. It then moves to heterochromatic chromocenters and co-localizes with Aurora-B and -C at the diplotene stage. Immunoprecipitation analyses showed that INCENP can form distinct complexes with either Aurora-C or Aurora-B in the testis. Together, these findings strongly support a model, in which INCENP recruits AuroraC and -B t
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