Daniel P Kiehart, Professor
We use multidisciplinary approaches to investigate the molecular mechanisms of cell sheet movements and actin appendage formation in morphogenesis and the cytoskeleton and motor proteins in hearing. Our studies range in scale from individual molecules to intact tissues in living animals.
Postdoctoral Fellow, Johns Hopkins University Medical School (Thomas D. Pollard, Advisor), 1982
Ph.D., Biology, University of Pennsylvania (Shinya Inoue, Advisor), 1979
B.A., Biology, University of Pennsylvania, 1973
- Office Hours:
- 5:30 to 6:30 PM Mondays
Cell and Molecular Biology
Research Categories: Biophysical approaches to cellular, molecular and developmental biology
Current projects: Cytoskeleton and motor protein function in morphogenesis and wound healing, Light activated gene expression, Filopodia function in morphogenesis and wound healing, Protein complex function in hearing
Research Description: Our intellectual focus is on identifying determinants of cell shape that function during development and wound healing. We utilize novel biophysical strategies (in collaboration with Glenn Edwards' group in Physics and with Stephanos Venakide's and John Harer's groups in Mathematics) in concert with modern molecular genetic and reverse genetic approaches in Drosophila to explore the forces that are responsible for cell shape change and movements. We show that both the amnioserosa and a "supracellular purse string" in the leading edge of the lateral epidermis contribute to the movements of dorsal closure. Dorsal closure proceeds even if we ablate one (but NOT both!)of the tissues responsible for closure, indicating that this model cell (epithelial) sheet movement depends on redundant forces that in concert drive morphogenesis. We show that the magnitude of each force is significantly larger than their vector sum indicating that there is both potential for generating large forces and that successful morphogenesis requires that the forces applied be precisely balanced. We have also explored the molecules responsible for generating those movements. We showed that conventional nonmuscle myosin (myosin II) provides key contractile forces in different tissues where the supramolecular complexes that incorporate this motor protein are distinct. How molecular events are regulated such that large, opposing forces efficiently drive morphogenesis remains a mystery, but we are pursuing leads that point to two distinct pathways: the bidirectionally signaling integrin cell surface receptors and mechanically gated channels.
We are also pursuing the morphogenesis of actin-cytoskeleton based projections that are a key feature of a variety of cells, including those that are specialized for sensory reception in human vision and hearing. We have again turned to Drosophila as a model system where we study the morphogenesis of epidermal hairs and sensory bristles. Our work centers on an unconventional myosin (myosin VIIA) encoded by crinkled a gene that is required for the formation of epidermal hairs and bristles. We show that myosin VIIA is required for the coallescence of actin pre-hairs into the robust actin bundles that form the skeleton on which hairs and bristles can be built. In collaboration with Dan Eberl's lab (University of Iowa) we showed that myosin VIIA is also essential for fly hearing -- remarkably, its human homolog is also required for human hearing, even though the mechanisms of auditory sensory reception in these phylogenetically diverged systems are very different. We have begun to characterize myosin VIIA structurally using NMR of purified protein domains. With Jim Seller's lab at the NIH we have used fast time course kinetics and single molecule assays to analyze molecular function and show that this myosin VIIA is a processive motor. We are beginning to characterize the proteins that collaborate with both myosin II and myosin VIIA using biochemical strategies in vitro, yeast two hybrid approaches in vivo and genetic interaction strategies in fly.
Together, our experiments promise to reveal the nature of cytoskeletal function in cell shape determination for cell division and morphogenesis throughout development and organismal homeostasis.
Areas of Interest:
motor protein structure and function
phylogeny of gene families
- Tulu, U.S., M.C. Beckerle and D.P. Kiehart, Cell Junctions and the Tension Sensitive, Supracellular Purse Strings in Drosophila Dorsal Closure, J. Cell Biol. (Submitted, June 20, 2012) (We are awaiting additional experimental data before resubmission..) .
- Hunter, G., J. Crawford, J. Genkins and D.P. Kiehart, Ion channels function in the mechanoregulation of cell sheet forces during Drosophila morphogenesis, Developmental Cell (Submitted, May, 2012) [author's comments].
- Roh-Johnson, M., G. Shemer, C.D. Higgins, J.H. McClennan, A.D. Werts, U.S. Tulu, L. Gao, E. Betzig, D.P. Kiehart and B. Goldstein, Triggering a Cell Shape Change by Exploiting Pre-Existing Actomyosin Contractions, Science, vol. In Press (January 20, 2012) [abs].
- Sokolow, A, Y. Toyama, D.P. Kiehart and G. Edwards, Cell ingression and apical shape oscillations during dorsal closure in Drosophila, Biophysical Journal, vol. In Press (January 17, 2012) [abs].
- MJ Boyle, RL French, KA Cosand, JB Dorman, DP Kiehart, CA Berg, Division of labor: subsets of dorsal-appendage-forming cells control the shape of the entire tube., Developmental Biology, vol. 346 no. 1 (October, 2010), pp. 68-79 [doi] [abs].