Last Updated: 12/22/2008

Research Interests
Telomeres, the ends of linear chromosomes, are usually composed of simple repetitive sequences. Telomeres are maintained by an enzyme called telomerase, which adds repeats to the end of a chromosome. Telomerase is absent from most normal human somatic cells, but is active in the vast majority of cancers, making it an attractive target for directed cancer therapy. We study telomerase using the nematode Caenorhabditis elegans. We also study genome rearrangements that occur at critically shortened telomeres, which may drive genome instability during tumor development.

Somatic cells may be deficient for processes that allow germ cells to proliferate from one generation to the next, indefinitely. Our research group also studies pathways that enable germ cells to combat proliferative aging; pathways that ensure germ cell immortality. Dysfunction of such pathways may lead to stem cell dysfunction in somatic cells or to transmission of epigenetic damage via germ cells, either of which may be relevant to oncogenesis.

Recent Accomplishments and Honors
We have demonstrated that the majority of end-to-end chromosome fusions may occur as a consequence of complex genome rearrangements.

Publications
Sebastien Greiss, Julie Hall, Shawn Ahmed and Anton Gartner (2008). C. elegans SIR-2.1 translocation is linked to a pro-apoptotic pathway parallel to cep-1/p53 during DNA damage induced apoptosis. Genes and Development 22: 2831-2842.

Mia Lowden, Teresa Lee, Bettina Meier, Julie Hall and Shawn Ahmed (2008). End-joining at Caenorhabditis elegans telomeres. Genetics 180: 741-754.

Julie Boerckel, Dana Walker and Shawn Ahmed (2007). The RFC-like subunit HPR-17 is required for telomere replication in C. elegans. Genetics 176: 703-709.

Shawn Ahmed (2006). Uncoupling of pathways that promote post-mitotic lifespan and apoptosis from replicative immortality of C. elegans germ cells. Aging Cell 5: 559-563.

Japser Harris, Mia Lowden, Iuval Clejan, Monika Tzoneva, James Thomas, Jonathan Hodgkin and Shawn Ahmed (2006). Mutator phenotype of C. elegans DNA damage checkpoint mutants. Genetics 174: 1-16. (Article Highlighted in October issue of Genetics)

Theresa Zucchero and Shawn Ahmed (2006). Genetics of proliferative aging. Experimental Gerontology 41: 992-1000.

Iuval Clejan, Julie Boerckel and Shawn Ahmed (2006). Developmental modulation of non-homologous end-joining in C. elegans. Genetics 173: 1301-1317.

Bettina Meier, Iuval Clejan, Yan Liu, Mia Lowden, Jonathan Hodgkin, and Shawn Ahmed (2005). trt-1 is the C. elegans catalytic subunit of telomerase. PLoS Genetics 2: e18.

Chris Smelick and Shawn Ahmed (2005). Achieving immortality in the C. elegans germline. Aging Research Reviews 4: 67-82.

Jacapo Novelli, Shawn Ahmed and Jonathan Hodgkin (2004). Gene interactions in Caenorhabditis elegans define DPY-31 as a candidate procollagen C-proteinase and SQT-3/ROL-4 as its predicted major target. Genetics 168: 1259-1273.

Shawn Ahmed, Arno Alpi, Michael Hengartner, Anton Gartner (2001). C. elegans RAD-5/CLK-2 defines a new DNA damage checkpoint protein. Submitted to Nature Genetics.

Bettina Meier and Shawn Ahmed (2001). Checkpoints: Meiotic chromosome pairing takes an unexpected twist. Current Biology, in press.

Shawn Ahmed and Jonathan Hodgkin (2000). MRT-2 checkpoint protein is required for germline immortality and telomere replication in C. elegans. Nature 403, 159-164. (note review in Nature - V. Lundblad (1994). A tale of ends. Nature 403, 149-150.)

Anton Gartner, Stuart Milstein, Shawn Ahmed, Jonathan Hodgkin and Michael O. Hengartner (2000). A conserved checkpoint pathway mediates DNA damage-induced apoptosis and cell cycle arrest in C. elegans. Molecular Cell 5, 435-443.

Shawn Ahmed, Hong Sheng, Luming Niu and Eric Henderson (1998). Tetrahymena mutants with short telomeres. Genetics 150, 643-650.

Shawn Ahmed, Augustin Kintanar and Eric Henderson (1994). Human telomeric C-strand tetraplexes. Nature Structural Biology 1, 83-88.
(note review in Nature - G. Riddihough (1994). The art of intercalation. Nature 367, 488.)

Shawn Ahmed and Eric Henderson (1992). Formation of novel hairpin structures by telomeric C-strand oligonucleotides. Nucleic Acids Research 20, 507-511.

E-mail: shawn@med.unc.edu
Address: 216 Fordham Hall Chapel Hill, NC 27599-3280

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