The hypodermis of adult wild-type worms is made up of several huge hyp-7 cells (or syncytia) which each contain 139 evenly spaced nuclei ( Shemer and Podbilewicz, 2000), making them a useful system for investigating nuclear anchorage. This model of how nuclear positioning works is primarily based on experiments in Caenorhabditis elegans worms with mutations in the genes for either the UNC-84 or ANC-1 protein ( Starr and Fridolfsson, 2010). The SUN and KASH domains of these proteins join together to form a bridge that mechanically couples the nucleus and cytoskeleton, which helps to anchor the nucleus in the right place ( Kim et al., 2015). The SUN proteins (SAD1, UNC-84) sit across the inner nuclear membrane and connect to structures in the nucleus, such as chromatin and the nuclear lamina, and the KASH proteins (Klarsicht, ANC-1, Syne Homology) span across the outer nuclear membrane and interact with proteins in the cytoskeleton. For example, mis-localization of the cell’s largest organelle, the nucleus, has been observed in neuromuscular diseases, such as Emery-Dreyfuss muscular dystrophy ( Luxton and Starr, 2014).Ĭurrent models suggest that positioning of the nucleus relies on a complex called LINC (short for Linker of Nucleoskeleton and Cytoskeleton), which is made up of proteins that contain either a SUN or KASH domain. To work correctly, most organelles need to be properly positioned within the cell.
Cells contain an assortment of organelles which each have their own specialized role.
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