Mark G Nielsen

Associate Professor; Chair
Full-Time Faculty
College of Arts and Sciences: Biology

Profile

Dr. Nielsen received his B.A. in Biology and Philosophy from Oberlin College in 1988 and was awarded his Ph.D. from Stanford University in Evolutionary Genetics in 1995. He then worked at Indiana University as a postdoctoral fellow, studying transcriptional factors in sea urchin development and then tubulin function and evolution in Drosophila. Since 2001, Dr. Nielsen has been an Assistant Professor at the University of Dayton, where he has continued his research on Drosophila. He also teaches for the Premedical Program and is the director of the Graduate Program in Biology.

View Curriculum Vitae (doc) >>

Faculty Perspective

Why do some phenotypes evolve, such as butterfly wing patterns, while others do not, such as 9+2 axoneme architecture? Natural selection could maintain an optimal phenotype, but another possibility exists, that alternate developmental mechanisms do not exist to produce variations in a phenotype. A fundamental component of Drosophila spermtail axonemes, b 2 tubulin, has not evolved in 80 million years. Is the protein an ideal configuration maintained by selection, or is it the only configuration able to support the extreme length of the Drosophila spermtail axoneme?

My laboratory investigates the structure/function relationship between Drosophila melanogaster b 2 and the spermtail axoneme in an evolutionary context. An evolutionarily conserved feature of the b 2 protein, the axoneme motif, specifies an evolutionarily conserved feature of motile axonemes, the central pair microtubules, while evolutionarily variable features of b 2, the carboxy terminus and internal variable region (IVR), influence an evolutionarily variable feature of spermtails, their length. Moreover, even the variable regions of the protein are not wholly free to evolve, due to synergism in the function of the IVR amino acids. These data reveal that there are exciting details to be discovered in how protein function relates to protein and ultimately phenotypic evolution.

Degrees

  • Ph.D., Stanford University 1995

Research Interests

  • Protein function and evolution
  • Evolutionary genetics
  • Molecular genetics

Selected Publications

Abueida, A., Nielsen, M.G. and Tam, T.Y. 2010. "Inverse spread limit of a non-negative matrix." Proyecciones Journal of Mathematics 29: 109-122.

Nielsen, M. G., Gadagkar, S., Griffiths, L. M. 2010. "Tubulin evolution in insects: gene duplication and subfunctionalization provide specialized isoforms in a functionally constrained gene family." BMC Evolutionary Biology 10:113.

Craver, E., McCrate, A., Nielsen, M. G., Swavey, S. 2010. "Tris-ruthenium(II)/copper(II) multimetallic porphyrin: Synthesis, characterization, DNA binding and supercoiled DNA photocleavage studies." Inorganica Chimica Acta 363: 453-456.

Posgai, R., Ahamed, M., Hussain, S. M., Rowe, J. J., Nielsen, M. G. 2009. "Inhalation method for systemic deliveryof nanoparticles to the Drosophila respiratory system for toxicity testing." Science of the Total Environment 408(2): 439-443.

Research Support

Nielsen, M. G. (Co-Principal), Rowe, J. J. (Principal), Robinson, J. B. (Co-Principle), Hong, T. (Co-Principal), "Nanoparticle Toxicity Tests in Model Systems," National Science Foundation G07R20573, $400,000.00 (2008 - 2010). We developed and applied multiple models (tissue culture, microbial, organismal) to test the toxicity of nanoparticles. I am responsible for the organismal (Drosophila) model.

Nielsen, M. G. (Co-Principal), Swavey, S. M. (Principal), Hong, Y. (Principal), Masthay, M. B. (Co-Principal), Robinson, J. B. (Co-Principal), "Development and Characterization of Ruthenium-substituted Porphyrins," Interdisciplinary Undergraduate Research Program American Association for the Advancement of Science/Merck Pharmaceuticals, $60,000.00 (2006 - 2009). We created an interdisciplinary, undergraduate research program to develop and test porphyrin-based photodynamic therapies. I am responsible for DNA-based assays of porphyrin cleavage activity, and development of the Drosophila IR model.

Department of Defense Consortium Research Fellows Program, $120,000 (2009-2012). Research Assistantship funding for my Ph.D. student Ryan Posgai, who developed the Drosophila nanoparticle toxicity model.

Nielsen, M. G. (Principal), "Developmental Constraint in Spermtail Evolution," National Science Foundation MCB-0316359, $170,000.00 (2003 - 2007). We determined that the mode and tempo of insect tubulin evolution is dictated by the rate of production of heritable variants, not competition among tubulin alleles.