XB-ART-51369J Biol Chem November 13, 2015; 290 (46): 27557-71.
Concentration-dependent Effects of Nuclear Lamins on Nuclear Size in Xenopus and Mammalian Cells.
A fundamental question in cell biology concerns the regulation of organelle size. While nuclear size is exquisitely controlled in different cell types, inappropriate nuclear enlargement is used to diagnose and stage cancer. Clarifying the functional significance of nuclear size necessitates an understanding of the mechanisms and proteins that control nuclear size. One structural component implicated in the regulation of nuclear morphology is the nuclear lamina, a meshwork of intermediate lamin filaments that lines the inner nuclear membrane. However, there has not been a systematic investigation of how the level and type of lamin expression influences nuclear size, in part due to difficulties in precisely controlling lamin expression levels in vivo. In this study, we circumvent this limitation by studying nuclei in Xenopus laevis egg and embryo extracts, open biochemical systems that allow for precise manipulation of lamin levels by the addition of recombinant proteins. We find that nuclear growth and size are sensitive to the levels of nuclear lamins, with low and high concentrations increasing and decreasing nuclear size, respectively. Interestingly, each type of lamin that we tested (lamins B1, B2, B3, and A) similarly affected nuclear size whether added alone or in combination, suggesting that total lamin concentration, and not lamin type, is more critical to determining nuclear size. Furthermore, we show that altering lamin levels in vivo, both in Xenopus embryos and mammalian tissue culture cells, also impacts nuclear size. These results have implications for normal development and carcinogenesis where both nuclear size and lamin expression levels change.
PubMed ID: 26429910
PMC ID: PMC4646008
Article link: J Biol Chem
Genes referenced: ckap2 gnl3 hist2h2be igf2bp3 lmnb1 lmnb3 ran
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|FIGURE 7. Cumulative Xenopus nuclear size data plotted as a function of total lamin concentration. Blue diamonds represent all in vitro data from experiments with egg extracts (Fig. 1C, 2B, 3B), red squares represent all in vitro and in vivo data from experiments with early stage embryos (Fig 4C, 5A), and green triangles represent all in vivo data from stage 11-12 embryos (Fig. 5C). The x- axis is total lamin concentration estimated by summing the ectopic lamin concentration (either added recombinant protein or protein expressed from microinjected mRNA) plus the endogenous lamin concentration for that stage of development.|