Centrosome attachment to the C. elegans male pronucleus is dependent on the surface area of the nuclear envelope

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2008.12.030 Byline: Marina Meyerzon (a), Zhizhen Gao (b), Jin Liu (a), Jui-Ching Wu (a), Christian J. Malone (b), Daniel A. Starr (a) Keywords: Nuclear envelope; Centrosome; Male pronucleus; Pronuclear migration; Lamin; LEM; BAF; Microtubule aster; Outer nuclear membrane; Dynein Abstract: A close association must be maintained between the male pronucleus and the centrosomes during pronuclear migration. In C. elegans, simultaneous depletion of inner nuclear membrane LEM proteins EMR-1 and LEM-2, depletion of the nuclear lamina proteins LMN-1 or BAF-1, or the depletion of nuclear import components leads to embryonic lethality with small pronuclei. Here, a novel centrosome detachment phenotype in C. elegans zygotes is described. Zygotes with defects in the nuclear envelope had small pronuclei with a single centrosome detached from the male pronucleus. ZYG-12, SUN-1, and LIS-1, which function at the nuclear envelope with dynein to attach centrosomes, were observed at normal concentrations on the nuclear envelope of pronuclei with detached centrosomes. Analysis of time-lapse images showed that as mutant pronuclei grew in surface area, they captured detached centrosomes. Larger tetraploid or smaller histone::mCherry pronuclei suppressed or enhanced the centrosome detachment phenotype respectively. In embryos fertilized with anucleated sperm, only one centrosome was captured by small female pronuclei, suggesting the mechanism of capture is dependent on the surface area of the outer nuclear membrane available to interact with aster microtubules. We propose that the limiting factor for centrosome attachment to the surface of abnormally small pronuclei is dynein. Author Affiliation: (a) Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA (b) Department of Biochemistry and Molecular Biology, Penn State University, University Park, PA 16802, USA Article History: Received 30 April 2008; Revised 13 December 2008; Accepted 19 December 2008