KRISTEN M. JOHANSEN, Associate Professor

Ph.D. Yale University, 1989

Department of ZOOLOGY and GENETICS

EMail: kristen@iastate.edu

Affiliations: GENETICS, MCDB, and NEUROSCIENCE programs, Signal Transduction Training Group.

 

Fields of Interest: Regulation of nuclear structure and function during cell division; developmental neurogenetics; molecular and functional characterization of neural antigens involved in axon guidance.

 

Recent advances in probing the organization of the nucleus have made it clear that nuclear structure is far more complex and ordered than had earlier been appreciated and that this structure may play a major role in cell function including gene expression and cell division. Our research is directed towards identifying the structural molecules defining nuclear organization, as well as the signal transduction pathways regulating cell cycle-specific changes. Using Drosophila as a model system, a combination of molecular and genetic approaches are being used to analyze genes involved in these processes. We have recently identified two novel nuclear antigens which show dynamic cell cycle-specific distribution patterns within the nucleus during mitosis. Preliminary molecular characterization has demonstrated that one of these antigens contains a highly unusual double kinase domain, suggesting that it may be involved in signaling within the nucleus. Using antibody staining techniques, we have identified a novel spindle-like scaffold which precedes and co-localizes with the microtubule spindle apparatus, and may serve a role in microtubule spindle assembly and/or function during mitosis. We are currently investigating the role of these antigens in determining nuclear structure and analyzing how they impact nuclear function.

 

A second research area in the laboratory addresses the question of how the nervous system develops and, in particular, the mechanisms by which axons find their targets. Whereas the human brain contains billions of neurons which must find specific targets, we are studying pathfinding in two much simpler systems, the leech and Drosophila. We are combining cloning, perturbation analysis, imaging techniques, and genetics to isolate and characterize molecules involved in axon fasciculation with the aim of determining how a relatively limited number of genes can code for the remarkable complexity and specificity of guidance mechanisms found in the nervous system.

These studies are done in collaboration with Dr. Jorgen Johansen

 

Selected References:

 

Johansen, K.M., R.G. Fehon & S. Artavanis-Tsakonas (1989) The Notch gene product is a surface glycoprotein expressed on the cell surface of both epidermal and neuronal precursor cells during Drosophila development. J. Cell. Biol. 109: 2427-2441.

Johansen, K.M., D.M. Kopp, J. Jellies and J. Johansen (1992) Tract formation and axon fasciculation of molecularly distinct peripheral neuron subpopulations during leech embryogenesis. Neuron 8: 559-572.

Johansen, K.M., and J. Johansen (1995) Filarin, a novel invertebrate intermediate filament protein present in axons and perikarya of developing and mature leech neurons. J. Neurobiol. 27 : 227-239.

Briggs, K.K., A.J. Silvers, K.M. Johansen & J. Johansen (1995) Calsensin: a novel calcium-binding protein expressed in a subset of peripheral leech neurons fasciculating in a single axon tract. J. Cell Biol. 129: 1355-1362.

Johansen, K.M. (1996) Dynamic remodeling of the nuclear architecture during the cell cycle. J. Cell. Biochem. 60: 289-296.

Johansen, K.M., J. Johansen, K.-H. Baek and Y. Jin (1996) Remodeling of nuclear architecture during the cell cycle in Drosophila embryos. J. Cell. Biochem. 63 : 268-279.

Johansen, J. and K.M. Johansen (1997) Molecular mechanisms mediating axon pathway formation. Crit. Rev. Eukaryotic Gene Expr. 7 : 95-116.

Huang, Y., J. Jellies, K.M. Johansen and J. Johansen (1997) Differential glycosylation of Tractin and LeechCAM, two novel Ig superfamily members, regulates neurite extension and fascicle formation. J. Cell Biol. 138 : 143-157.

Huang, Y., J. Jellies, K.M. Johansen and J. Johansen (1998) Development and pathway formation of peripheral neurons during leech embryogenesis. J. Comp. Neurol. 397 : 394-402.

Weiss, J.L., J. Yang, C. Jie, D.L. Walker, S. Ahmed, Y. Zhu, Y. Huang, K.M. Johansen and J. Johansen (1999) Molecular cloning and characterization of LKv1, a novel voltage-gated potassium-channel in leech. J. Neurobiol. (in press)

Drosophila syncytial nuclei triple-labeled with mAb2A, lamin antibody and Hoechst