Reversal of age-dependent nuclear morphology by inhibition of prenylation does not affect lifespan in Caenorhabditis elegans

Abstract

Fibroblasts derived from Hutchinson-Gilford progeria syndrome (HGPS) patients and dermal cells derived from healthy old humans in culture display age-dependent progressive changes in nuclear architecture due to accumulation of farnesylated lamin A. Treating human HGPS cells or mice expressing farnesylated lamin A with farnesyl transferase inhibitors (FTIs) reverses nuclear phenotypes and extends lifespan. Aging adult Caenorhabditis elegans show changes in nuclear architecture resembling those seen in HGPS fibroblasts, as well as a decline in motility, phenotypes which are also inhibited by the FTI gliotoxin. However, it was not clear whether these effects were due to loss of farnesylation or to side effects of this drug. Here, we used a different FTI, manumycin, or downregulated polyprenyl synthetase with RNAi to test the roles of farnesylation in C. elegans aging. Our results show that the age-dependent changes in nuclear morphology depend on farnesylation. We also demonstrate that inhibition of farnesylation does not affect motility or lifespan, suggesting that the effects of blocking protein prenylation on nuclear morphology could be separated from their effects on motility and lifespan. These results provide further understanding of the role of lamin and farnesylation in the normal aging process and in HGPS.

Acknowledgements

We thank Dr. Erin Bank for excellent comments. This study was funded by grants from the Israel Science Foundation, USA-Israel Binational Science Foundation (BSF), German-Israel Foundation (GIF), the Legacy (Morasha) fund of the Israeli Science Foundation and the Muscular Dystrophy Association (MDA). Some nematode strains used in this work were provided by the Caenorhabditis Genetics Center, which is funded by the NIH National Center for Research Resources (NCRR).

Figures and Tables

Figure 1 Manumycin alters nuclear morphology. GFP::Ce-lamin in live control and manumycin treated worms at days 4 (upper part) and 6 (lower part) of adulthood. C. elegans were treated with 125, 250 and 500 nM of manumycin and grown at 20°C. Nuclei in worms treated with manumycin show fewer convolutions compared to nuclei from untreated worms. Bar = 10 microns and applies to all parts.

Figure 2 Manumycin affects motility and is toxic to C. elegans. (A) Relative motility of control and manumycin-treated worms. Black bars indicate control; dark gray bars 125 nM manumycin and light gray bars 250 nM of manumycin. Y-axis shows relative average motility to control worms at day 1 of adulthood. (B) Survival plot of control and manumycin treated animals. The amount of manumycin is indicated next to each graph. The animal lifespan was shortened with increased doses of manumycin.

Figure 3 Nuclei retain their round morphology following polyprenyl synthetase downregulation by fdps-1(RNAi). (A) Animals were treated with either the empty vector L4440 (EV) or with fdps-1(RNAi) starting at the young adult stage (day 1). GFP::Ce-lamin was used to view changes in nuclear and nuclear envelope shapes. The fdps-1(RNAi)-treated nuclei showed some lamin aggregations at the nuclear periphery, but no lobulation. Bars = 10 microns.

Figure 4 Downregulation of polyprenyl synthetase by fdps-1(RNAi) blocks the redistribution of chromatin in nuclei of aging cells. Animals were treated with either L4440 vector (EV) or with fdps-1(RNAi) starting at the young adult stage (day 1). Ce-emerin::GFP and Hoechst DNA staining were used to view changes in nuclear envelope shapes and chromatin distribution. fdps-1(RNAi)-treated worms show diminished chromatin mislocalization at old age. In the merge parts green = lamin; blue = DNA. Bars = 10 microns.

Figure 5 Downregulation of polyprenyl synthetase by fdps-1(RNAi) has no significant effect on motility and lifespan. (A) Relative motility of control (dark gray) and fdps-1(RNAi) (light gray)-treated worms. (B) Survival plot of control- and fdps-1(RNAi)-treated animals. The black line indicates control and the light gray line fdps-1(RNAi).