Dr. Nels Elde

Nels grew up in the city of lakes, Minneapolis, Minnesota along with a younger sister, brother, and a multitude of pets. He migrated south to Northfield, Minnesota for his undergraduate years at Carleton College. There he completed a bachelor´s degree in Biology, and continued at Carleton as a research technician in the lab of Stephan Zweifel, pursuing genetic studies in yeast and leaf-cutting ant fungus. Before entering graduate school, he took a position as an Associate Scientist at Medtronic, Inc., a medical device company headquartered in Minneapolis. As a Ph.D. student in the laboratory of Aaron Turkewitz at the University of Chicago, his thesis research focused on molecular genetic and evolutionary studies of endocytosis in the model ciliate, Tetrahymena thermophila.

In the Malik lab, Nels is investigating adaptive evolution at host-pathogen interfaces. One such interaction is between Protein Kinase R (PKR) and a poxvirus-encoded mimic of its substrate called K3L. In general, kinases don’t evolve rapidly since they must interact with highly conserved substrates. PKR’s substrate, called eIF2a, is well conserved. However, its phosphorylation by PKR leads to a dramatic block in protein translation, which prevents viral spread in infected cells. Viruses have evolved a variety of countermeasures to overcome this PKR-mediated block in translation, including competitive inhibition of eIF2a by mimics like K3L. Such antagonistic host-pathogen interactions can lead to repeated bouts of adaptive evolution and provide a window into determining mechanisms of substrate recognition.

Nels is also studying rapidly evolving proteins associated with telomeres in Drosophila. Unlike the vast majority of eukaryotes that maintain chromosomal ends with telomerase, Drosophila depends on the recruitment of active retrotransposons to telomeres to replenish these vital regions of the genome. Little is known about how these retrotransposons are targeted exclusively to the ends of chromosomes. However, rapidly evolving telomere proteins from this system provide important clues for uncovering details about this remarkable strategy for protecting chromosomes by co-opting otherwise autonomous genetic elements.

    When not working on the science, Nels enjoys canoeing, soccer, fishing, jazz music, basketball, shellfish, television (reality based programming and situational comedies), jogging, quilting, cactus collecting, the "internet," sand volleyball, cooking, supervising pets, great-blue herons, public radio, swimming, and robots.

Research Papers

1. Elde N.C., Long M., Turkewitz A.P. (2007) A role for convergent evolution in the secretory life of cells. Trends in Cell Biology. Apr;17(4):157-164. PDF file 544 kb
2. Eisen J.A., Coyne R.S., Wu M., Wu D., Thiagarajan M., Wortman J.R., Badger J.H., Ren Q., Amedeo P., Jones K.M., Tallon L.J., Delcher A.L., Salzberg S.L., Silva J.C., Haas B.J., Majoros W.H., Farzad M., Carlton J.M., Smith R.K. Jr., Garg J., Pearlman R.E., Karrer K.M., Sun L., Manning G., Elde N.C., Turkewitz A.P., Asai D.J., Wilkes D.E., Wang Y., Cai H., Collins K., Stewart B.A., Lee S.R., Wilamowska K., Weinberg Z., Ruzzo W.L., Wloga D., Gaertig J., Frankel J., Tsao C.C., Gorovsky M.A., Keeling P.J., Waller R.F., Patron N.J., Cherry J.M., Stover N.A., Krieger C.J., del Toro C., Ryder H.F., Williamson S.C., Barbeau R.A., Hamilton E.P., Orias E. (2006) Macronuclear genome sequence of the ciliate Tetrahymena thermophila, a model eukaryote. PLoS Biology Sep;4(9):e286 PDF file 953 kb.
3. Elde N.C., Morgan G., Winey M., Sperling L., Turkewitz A.P. (2005) Elucidation of clathrin-mediated endocytosis in Tetrahymena reveals an evolutionarily convergent recruitment of dynamin. PLoS Genetics, 1: e52. PDF file 5 mb.
4. Bowman G.R., Elde N.C., Morgan G., Winey M., Turkewitz A.P. (2005) Core formation and the acquistion of fusion competence are linked during secretory granule maturation in Tetrahymena. Traffic, 6: 303-323. PDF file 12.9 mb
5. Doherty K.R., Zweifel E.W., Elde N.C., McKone M.J., Zweifel S.G. (2003) Random amplified polymorphic DNA markers reveal genetic variation in the symbiotic fungus of leaf-cutting ants. Mycologia, 95: 19-23. PDF file 341 kb
6. Chilcoat N.D., Elde N.C., Turkewitz A.P. (2001) An antisense approach to phenotype-based gene cloning in Tetrahymena. Proc Natl Acad Sci U S A., 98: 8709-13. PDF file 193 kb

Cinematography

1. The predatory ciliate, Lacrymaria olor, hunting and devouring its prey, Tetrahymena thermophila, (2002) Quicktime video (6.0 MB)

Act 1. Lacrymaria olor is a freshwater ciliate commonly found in ponds and streams. Here a Lacrymaria cell is shown extending its “proboscis” as it probes its surroundings for a meal. The “proboscis” can extend up to 7 times the length of the cell body.

Act 2. Tetrahymena thermophila, another ciliate, swims near Lacrymaria and is in jeopardy of being captured and eaten.

Act 3. Lacrymaria catches and devours Tetrahymena. After making contact, dense core secretory granules are released from the “proboscis,” which paralyze and begin digesting Tetrahymena. The “proboscis” is quickly remodeled to open and ingest the prey. This video clip is in real time.

Act 4. After eating a Tetrahymena or two, Lacrymaria is unable to capture more cells until its secretory granules are replenished. A captured Tetrahymena cell is evident in the cell body of Lacrymaria, and is being digested in a phagosome.

 Nels Elde