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Cnn Dynamics Drive Centrosome Size Asymmetry to Ensure Daughter Centriole Retention in Drosophila Neuroblasts

2010; Elsevier BV; Volume: 20; Issue: 24 Linguagem: Inglês

10.1016/j.cub.2010.11.055

1879-0445

Paul T. Conduit, Jordan W. Raff,

Plant Molecular Biology Research

Centrosomes comprise a pair of centrioles surrounded by an amorphous network of pericentriolar material (PCM). In certain stem cells, the two centrosomes differ in size, and this appears to be important for asymmetric cell division [1Rebollo E. Sampaio P. Januschke J. Llamazares S. Varmark H. González C. Functionally unequal centrosomes drive spindle orientation in asymmetrically dividing Drosophila neural stem cells.Dev. Cell. 2007; 12: 467-474Abstract Full Text Full Text PDF PubMed Scopus (221) Google Scholar, 2Rusan N.M. Peifer M. A role for a novel centrosome cycle in asymmetric cell division.J. Cell Biol. 2007; 177: 13-20Crossref PubMed Scopus (182) Google Scholar]. In some cases, centrosome asymmetry is linked to centriole age because the older, mother centriole always organizes more PCM than the daughter centriole, thus ensuring that the mother centriole is always retained in the stem cell after cell division [3Yamashita Y.M. Mahowald A.P. Perlin J.R. Fuller M.T. Asymmetric inheritance of mother versus daughter centrosome in stem cell division.Science. 2007; 315: 518-521Crossref PubMed Scopus (402) Google Scholar]. This has raised the possibility that an “immortal” mother centriole may help maintain stem cell fate [4Morrison S.J. Spradling A.C. Stem cells and niches: Mechanisms that promote stem cell maintenance throughout life.Cell. 2008; 132: 598-611Abstract Full Text Full Text PDF PubMed Scopus (1346) Google Scholar, 5Yamashita Y.M. Fuller M.T. Asymmetric centrosome behavior and the mechanisms of stem cell division.J. Cell Biol. 2008; 180: 261-266Crossref PubMed Scopus (106) Google Scholar]. It is unclear, however, how centrosome size asymmetry is generated in stem cells. Here we provide compelling evidence that centrosome size asymmetry in Drosophila neuroblasts is generated by the differential regulation of Cnn incorporation into the PCM at mother and daughter centrioles. Shortly after centriole separation, mother and daughter centrioles organize similar amounts of PCM, but Cnn incorporation is then rapidly downregulated at the mother centriole, while it is maintained at the daughter centriole. This ensures that the daughter centriole maintains its PCM and so its position at the apical cortex. Thus, the daughter centriole, rather than an “immortal” mother centriole, is ultimately retained in these stem cells.