Areas of Research: Molecular mechanisms of aging
148 Carl C. Icahn Laboratory
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.
- Shi C, Murphy CT. (2014) Mating induces shrinking and death in Caenorhabditis mothers. Science. 343: 536-40. Pubmed
- Tepper RG, Murphy CT, Bussemaker HJ. (2014) DAF-16 and PQM-1: Partners in longevity. Aging (Albany NY) 6: 5-6 Pubmed
- Murphy CT, Hu PJ. (2013) Insulin/insulin-like growth factor signaling in C. elegans. WormBook. 1-43. Pubmed
- Tepper RG, Ashraf J, Kaletsky R, Kleemann G, Murphy CT, Bussemaker HJ. (2013) PQM-1 complements DAF-16 as a key transcriptional regulator of DAF-2-mediated development and longevity. Cell. 154: 676-90. PubMed
- Blackstone C, Murphy CT. (2012) Cell biology of disease and aging: a two-way street. Mol Biol Cell. 23: 975.
- Stein GM, Murphy CT. (2012) The intersection of aging, longevity pathways, and learning and memory in C. elegans. Front Genet. 3: 259. Pubmed
- Rizki G, Iwata TN, Li J,...Murphy CT, Lee SS. (2011) The evolutionarily conserved longevity determinants HCF-1 and SIR-2.1/SIRT1 collaborate to regulate DAF-16/FOXO. PLoS Genet. 7:e1002235. PubMed
- Liu G, Rogers J, Murphy CT, Rongo C. (2011) EGF signaling activates the ubiquitin proteasome system to modulate C. elegans lifespan. EMBO J. 30: 2990-3003. Pubmed
- Kauffman A, Parsons L, Stein G, Wills A, Kaletsky R, Murphy C. (2011) C. elegans positive butanone learning, short-term, and long-term associative memory assays. J Vis Exp. pii: 2490. Pubmed
- Luo S, Murphy CT. (2011) C. elegans reproductive aging: Regulation and underlying mechanisms. Genesis. 49: 53-65. PubMed
- Murphy CT. (2010) Aging: miRacles of Longevity? Curr Biol. 20: R1076-78. 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: 415-19. PubMed
- Landis JN, Murphy CT. (2010) Integration of diverse inputs in the regulation of Caenorhabditis elegans DAF-16/FOXO. Dev Dyn. 239: 1405-12. 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: 1635-45. PubMed
- Murphy CT. (2006) The search for DAF-16/FOXO transcriptional targets: Approaches and discoveries. Exp Gerontol. 41: 910-21. 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, Murphy CT. (2006) Enrichment of regulatory motifs upstream of predicted DAF-16 targets. Nat Genet. 38: 397-98. PubMed
- McCarroll SA, Murphy CT, Zou S,...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,...Kenyon C. (2003) Genes that act downstream of DAF-16 to influence the lifespan of Caenorhabditis elegans. Nature. 424: 277-83. PubMed
- Hsu AL, Murphy CT, Kenyon C. (2003) Regulation of aging and age-related disease by DAF-16 and heat-shock factor. Science. 300: 1142-45. PubMed
- Murphy CT, Rock RS, Spudich JA. (2001) A myosin II mutation uncouples ATPase activity from motility and shortens step size. Nat Cell Biol. 3: 311-15. PubMed
- Murphy CT, Spudich JA. (2000) Variable surface loops and myosin activity: accessories to a motor. J Muscle Res Cell Motil. 21: 139-51. PubMed
- Murphy CT, 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: 3785-92. PubMed
- Murphy CT, Spudich JA. (1998) Dictyostelium myosin 25-50K loop substitutions specifically affect ADP release rates. Biochemistry. 37: 6738-44. PubMed