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Centrosomes are major microtubule organizing centers (MTOCs) that play an important role in chromosome segregation during cell division. Centrosomes provide a stable anchor for microtubules, constituting the centers of the spindle poles in mitotic cells, and determining the orientation of cell division. However, visualization of centrosomes is challenging because of their small size. Especially in mouse tissues, it has been extremely challenging to observe centrosomes belonging to a specific cell type of interest among multiple comingled cell types. To overcome this obstacle, we generated a tissue-specific centrosome indicator. In this mouse line, a construct containing a floxed neomyocin resistance gene with a triplicate polyA sequence followed by an EGFP-Centrin1 fusion cassette was knocked into the Rosa locus. Upon Cre-mediated excision, EGFP-Centrin1 was expressed under the control of the Rosa locus. Experiments utilizing mouse embryo fibroblasts (MEFs) demonstrated the feasibility of real-time imaging, and showed that EGFP-Centrin1 expression mirrored the endogenous centrosome cycle, undergoing precisely one round of duplication through the cell cycle. Moreover, experiments using embryo and adult mouse tissues demonstrated that EGFP-Centrin1 specifically mirrors the localization of endogenous centrosomes. genesis 54:286-296, 2016. © 2016 The Authors. Genesis Published by Wiley Periodicals, Inc.

Centrosomes are major microtubule organizing centers (MTOCs) that play an important role in chromosome segregation during cell division. Centrosomes provide a stable anchor for microtubules, constituting the centers of the spindle poles in mitotic cells, and determining the orientation of cell division. However, visualization of centrosomes is challenging because of their small size. Especially in mouse tissues, it has been extremely challenging to observe centrosomes belonging to a specific cell type of interest among multiple comingled cell types. To overcome this obstacle, we generated a tissue-specific centrosome indicator. In this mouse line, a construct containing a floxed neomyocin resistance gene with a triplicate polyA sequence followed by an EGFP-Centrin1 fusion cassette was knocked into the Rosa locus. Upon Cre-mediated excision, EGFP-Centrin1 was expressed under the control of the Rosa locus. Experiments utilizing mouse embryo fibroblasts (MEFs) demonstrated the feasibility of real-time imaging, and showed that EGFP-Centrin1 expression mirrored the endogenous centrosome cycle, undergoing precisely one round of duplication through the cell cycle. Moreover, experiments using embryo and adult mouse tissues demonstrated that EGFP-Centrin1 specifically mirrors the localization of endogenous centrosomes. genesis 54:286-296, 2016. © 2016 The Authors. Genesis Published by Wiley Periodicals, Inc.

Understanding cardiomyocyte cell cycle regulation after birth is key to optimizing regenerative strategies for the heart post-injury, yet poses multiple technical challenges, as evidenced by recent studies that have arrived at divergent conclusions. In a recent publication in Cell, Alkass et al undertook multiple approaches to examine cardiomyocyte cell cycle regulation in the first three weeks after birth. Here, we summarize results of Alkass et al and three other groups in examining preadolescent cardiomyocyte cell cycle regulation, highlighting the distinct approaches and incumbent caveats.

Centrosomes are microtubule-organizing centers that facilitate bipolar mitotic spindle assembly and chromosome segregation. Recognizing that centrosome amplification is a common feature of aneuploid cancer cells, we tested whether supernumerary centrosomes are sufficient to drive tumor development. To do this, we constructed and analyzed mice in which centrosome amplification can be induced by a Cre-recombinase-mediated increase in expression of Polo-like kinase 4 (Plk4). Elevated Plk4 in mouse fibroblasts produced supernumerary centrosomes and enhanced the expected mitotic errors, but proliferation continued only after inactivation of the p53 tumor suppressor. Increasing Plk4 levels in mice with functional p53 produced centrosome amplification in liver and skin, but this did not promote spontaneous tumor development in these tissues or enhance the growth of chemically induced skin tumors. In the absence of p53, Plk4 overexpression generated widespread centrosome amplification, but did not drive additional tumors or affect development of the fatal thymic lymphomas that arise in animals lacking p53. We conclude that, independent of p53 status, supernumerary centrosomes are not sufficient to drive tumor formation.