Molecular Biology Faculty
Coleen T. Murphy
|Murphy Research Lab|
Carl Icahn Lab, 148
Lab (609) 258-9396
Molecular mechanisms of aging
My lab is focused on the process of aging, which remains one of the fundamental mysteries of biology. While aging may appear to be simply an unfortunate consequence of living, recent genetic breakthroughs suggest that aging is a regulated process, rather than the result of cumulative cellular damage. Many chronic and degenerative disorders, such as diabetes, cancer, and neurodegenerative diseases develop in an age-related manner. Because more than 20% of U.S. citizens will be over the age of 65 by the year 2050, there is a growing need to better understand the mechanisms involved in aging and age-associated diseases.
The emergence of model systems to study aging and the development of whole-genome approaches is providing an unprecedented glimpse into the processes underlying aging. Our understanding of aging at the molecular level will progress from identifying these global regulators, to defining the genes that they control, to describing the biochemical events that carry out the business of keeping an organism's cells alive. The goal of my lab is to enrich our understanding of the molecular basis of aging process by first identifying the genes that are controlled by these global regulators and then elucidating the cell biological and biochemical mechanisms used by these genes to affect lifespan.
A model for aging: C. elegans
- We have chosen the nematode C. elegans as our model system of aging. For our purposes C. elegans is ideal because lives two-three weeks, making lifespan experiments feasible, and during this time it exhibits many obvious phenotypes of aging, such as slowed motility and tissue deterioration. Importantly, C. elegans mutants with dramatically extended longevity have been identified; the genetic dissection of the pathways contributing to these mutants' longevity can shed light on the mechanisms of aging. The genes that regulate lifespan are conserved from worms to mammals, making our findings relevant for humans, as well.
Transcriptional analysis of longevity pathways
The initial work in my lab will use microarray techniques to identify transcriptional targets of longevity pathways. For this purpose, we have built both PCR product arrays and 60-mer oligo arrays for the almost 20,000 open reading frames in C. elegans. My previous work identified the genes that act downstream of the C. elegans insulin receptor/FOXO transcription factor pathway, and found that this pathway is likely to be regulated through a feed-forward mechanism; now we would like to determine when the target genes are expressed and distinguish direct from indirect targets. Because downregulation of the insulin receptor pathway is only one of the mechanisms that increase the longevity of C. elegans, we will also use microarrays and genomic analysis to discover transcriptional targets that are shared between multiple longevity pathways.
Functional analysis of candidate lifespan genes
Once the targets have been identified, we can use the extremely tractable C. elegans experimental system to test these genes for their roles in longevity. For example, C. elegans is susceptible to RNA interference by bacterial feeding, allowing us to quickly knock down gene activity and test the requirement for that gene in lifespan extension. Now that we know which genes act downstream of the insulin receptor/FOXO pathway to affect lifespan, we would like to identify the sites of action of these genes in the worm. Using fluorescent gene fusions, we can identify the localization and time of expression of specific proteins in the animal to better understand the gene's organismal role. Finally, in vitro studies will be carried out on the most interesting candidate genes to understand their biochemical functions.
Additionally, my lab will carry out genetic screens to identify novel genes that are critical to aging-related processes. The combination of a classic genetic system that recapitulates aging in higher organisms with powerful genomic approaches and fast functional analysis should help us to elucidate the multigenic mechanisms involved in aging.
Tepper RG, Ashraf J, Kaletsky R, Kleemann G, Murphy CT, Bussemaker HJ. (Aug 1, 2013) PQM-1 complements DAF-16 as a key transcriptional regulator of DAF-2-mediated development and longevity. Cell. 154(3):676-90. doi: 10.1016 /j.cell. 2013.07.006. PubMed
Blackstone C and Murphy CT (March 15, 2012). "Cell biology of disease and aging: a two-way street." Molecular Biology of the Cell, v 23, no 975 10.1091/mbc.E11-12-0985 Molecular Biology of the Cell
Stein GM and Murphy CT (2012) . "The intersection of aging, longevity pathways, and learning and memory in C. elegens." Front. Gene. 3:259. doi: 10.3389/fgene.2012. 0259 Frontiers in Genetics and Aging
Rizki, G., Iwata, T.N., Li, J., Riedel, C.G., Picard, C.L., Jan, M., Murphy, C.T., and Lee, S.S. (2011) "The Evolutionarily conserved longevity determinants HCF-1 and SIR-2.1/SIRT1 collaborate to regulate DAF-16/FOXO." PLoS Genetics, 2011 Sep;7(9):e1002235. Epub 2011 Sep 1. PubMed
Liu, G., Rogers, J., Murphy, C. T., and Rongo, C. “EGF signaling activates the ubiquitin proteasome system to modulate C. elegans lifespan.” (2011) EMBO J.June 14. doi: 10.1038/emboj.2011.195. PubMed
Kauffman, A.L., Parsons, L., Stein, G.M., Wills, A.A., Kaletsky, R.L., and Murphy, C.T., “C. elegans Positive Butanone Learning, Short-term, and Long-term Associative Memory Assays.” (2011) J. Vis. Exp. 49 PubMed
Luo, S. and Murphy, C.T., “C. elegans Reproductive Aging: Regulation and Underlying Mechanisms.” (2011) Genesis Feb;49(2):53-65. doi: 10.1002/dvg.20694. Epub 2011 Jan 2 PubMed
Murphy CT. (2010) Aging: miRacles of Longevity? Curr Biol. 20: R1076-1078. PubMed
Luo S, Kleemann GA, Ashraf JM, Shaw WM, Murphy CT. (2010) TGF-β and insulin signaling regulate reproductive aging via oocyte and germline quality maintenance. Cell. 143: 299-312. PubMed
Kauffman AL, Ashraf JM, Corces-Zimmerman MR, Landis JN, Murphy CT. (2010) Insulin signaling and dietary restriction differentially influence the decline of learning and memory with age. PLoS Biol. 8: e1000372. PubMed
Kaletsky R, Murphy CT. (2010) The role of insulin/IGF-like signaling in C. elegans longevity and aging. Dis Model Mech. 3: 415-419. PubMed
Landis JN, Murphy CT. (2010) Integration of diverse inputs in the regulation of Caenorhabditis elegans DAF-16/FOXO. Dev Dyn. 239: 1405-1412. PubMed
Luo S, Shaw WM, Ashraf J, Murphy CT. (2009) TGF-beta Sma/Mab signaling mutations uncouple reproductive aging from somatic aging. PLoS Genet. 5: e1000789. PubMed
Chikina MD, Huttenhower C, Murphy CT, Troyanskaya OG. (2009) Global prediction of tissue-specific gene expression and context-dependent gene networks in Caenorhabditis elegans. PLoS Comput Biol. 5: e1000417. PubMed
Kleemann GA, Murphy CT. (2008) The endocrine regulation of aging in Caenorhabditis elegans.Mol Cell Endocrinol. 299: 51-57. PubMed
Shaw WM, Luo S, Landis J, Ashraf J, Murphy CT. (2007) The C. elegans TGF-beta Dauer pathway regulates longevity via insulin signaling. Curr Biol 17: 1635-1645. PubMed
Murphy CT (2006). The search for DAF-16/FOXO transcriptional targets: Approaches and discoveries. Exp Gerontol. 41: 910-921. PubMed
Murphy CT (2006). Using whole-genome transcriptional analyses to discover molecular mechanisms of aging. Drug Discovery Today: Disease Mechanisms 3: 41-46.
Kenyon C and Murphy CT (2006). Enrichment of regulatory motifs upstream of predicted DAF-16 targets. Nat Genet 38: 397-398. PubMed
McCarroll SA, Murphy CT, Zou S, Pletcher SD, Chin CS, Jan YN, Kenyon C, Bargmann CI, Li H (2004). Comparing genomic expression patterns across species identifies shared transcriptional profile in aging. Nat Genet 36: 197-204. PubMed
Murphy CT, McCarroll SA, Bargmann CI, Fraser A, Kamath RS, Ahringer J, Li H, Kenyon C (2003). Genes that act downstream of DAF-16 to influence the lifespan of Caenorhabditis elegans. Nature 424: 277-283. PubMed
Hsu AL, Murphy CT and Kenyon C (2003). Regulation of aging and age-related disease by DAF-16 and heat-shock factor. Science 300: 1142-1145. PubMed
Murphy CT, Rock RS and Spudich JA (2001). A myosin II mutation uncouples ATPase activity from motility and shortens step size. Nat Cell Biol 3: 311-315. PubMed
Murphy CT and Spudich JA (2000). Variable surface loops and myosin activity: accessories to a motor. J Muscle Res Cell Motil 21: 139-151. PubMed
Murphy CT and Spudich JA (1999). The sequence of the myosin 50-20K loop affects Myosin's affinity for actin throughout the actin-myosin ATPase cycle and its maximum ATPase activity. Biochemistry 38: 3785-3792. PubMed
Murphy CT and Spudich JA (1998). Dictyostelium myosin 25-50K loop substitutions specifically affect ADP release rates. Biochemistry 37: 6738-6744. PubMed