title: Differences in the origins of kinetochore-positive and kinetochore-negative micronuclei: A live cell imaging study.
abstract: Micronuclei (MNi) are extensively used to evaluate genotoxicity and chromosomal instability. Classification of kinetochore-negative (K-MNi) and kinetochore-positive micronuclei (K+MNi) improves the specificity and sensitivity of the micronucleus (MN) test; however, the fundamental differences in the origins of K-MNi and K+MNi have not been addressed due to the limitations of traditional methods. In the current study, HeLa CENP B-GFP H2B-mCherry cells were constructed in which histone 2B (H2B) and centromere protein B (CENP B) were expressed as fusion proteins to monomeric Cherry (mCherry) and EGFP, respectively. MNi were identified using H2B-mCherry; K+MN contained CENP B-GFP, while K-MN did not. Long-term live cell imaging was conducted to examine MN formation in the dual-color fluorescent HeLa cells. The results suggested that K-MNi were derived from kinetochore-negative displaced chromosomes (K-DCs), kinetochore-negative lagging chromosomes (K-LCs) and fragments of broken chromosome bridges (CBs) during late mitotic stages. The results also indicated that K+MNi are derived from kinetochore-positive displaced chromosomes (K+DCs), kinetochore-positive lagging chromosomes (K+LCs), and fragments of broken CBs. Different aberrant chromosomes emerged during mitosis at different frequencies and developed into K-MNi and/or K+MNi in the daughter cells at different rates. K+LCs formed K+MNi at a higher frequency than K+DCs, and K-LCs formed K-MNi at a higher rate than K-DCs; however, broken CBs transformed into K-MNi and/or K+MNi. In summary, these results show that K-MNi and K+MNi have different origins in HeLa cells and that each mechanism of MN formation contributes differently to the overall number of K-MNi and K+MNi.
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agriculture University, Hefei, Anhui 230036, People's Republic of China. Electronic address: erkangj@ustc.edu.cn.
authors.forename: Erkang
authors.initials: E
authors.lastname: Jiang
mesh_terms: D000705:Anaphase; D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D051936:Centromere Protein B / Q000378:metabolism; D004249:DNA Damage; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000502:physiology*; D015162:Micronucleus Tests; D013692:Telophase
chemical_list: D051936:Centromere Protein B
keywords: Kinetochore; Live cell imaging; Micronuclei; Micronucleus origin