This work demonstrates a remarkably tight link between nuclear and cell size throughout a wide variety of cell sizes and physiological conditions, and suggests there is a general cellular control linking nuclear growth to cell size. Here we report a detailed analysis of the coordination between nuclear and cell growth in the fission yeast Schizosaccharomyces pombe. Recent work in budding yeast has shown that nuclear and cell size correlate in cell size mutants as well as throughout the cell cycle and in diploid cells ( Jorgensen et al., 2007). In contrast to metazoan cells, yeasts do not reassemble the nuclear envelope (NE) after mitosis and thus provide simple models to study the regulation of nuclear size in a single cell. However, it does not explain well how large changes in cell size and nuclear size can occur between cells within a single organism, often linked to differentiation or developmental programs of the cell ( Sato et al., 1994 Taddei et al., 2004 Brandt et al., 2006). One idea for nuclear size control is the nucleoskeletal theory, which states that nuclear volume is determined by the amount of DNA, the degree of DNA compaction, the amount and composition of nuclear membranes, and in metazoa the components of the nuclear lamina ( Orgel and Crick, 1980 Cavalier-Smith, 1982 Gregory, 2005). Positive correlations among nuclear size, cell size, genome size, ploidy, or generation times have been described, often comparing a diverse range of species, although mechanistic explanations have remained elusive ( Schmidt and Schibler, 1995 Gregory, 2005 Jovtchev et al., 2006). Based on work on sea urchin embryos and algae he proposed the “Kern-Plasma-Relation” or karyoplasmic ratio, as a constant characteristic for every cell type ( Gerassimow, 1902 Boveri, 1905). In 1903 Richard Hertwig formulated the first quantitative hypothesis about organelle size ( Hertwig, 1903). Despite over 100 years of research it remains poorly understood how nuclear size is regulated. The nucleus is a good organelle to study this problem because it is usually present as a single organelle in each cell and is easy to visualize accurately. Although progress has been made in understanding the biochemical mechanisms underlying how membranes are formed and shaped, little is known about how the overall sizes of these organelles are determined ( Nurse, 1975, 1985 Marshall, 2004 Umen, 2005 Zimmerberg and Kozlov, 2006). The sizes of membrane-bound organelles are important for eukaryotic cell organization and function.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |