Area of Research
Cell Specification and Differentiation, Neural Degeneration and Repair, Stem Cell Biology, Axon Pathfinding and Synaptogenesis
Motor proteins in brain developmental disease, neurogenesis, axonal transport, and growth cone function
Cytoplasmic dynein is a large microtubule motor protein, which is responsible for retrograde axonal transport and neurotrophin signaling. It is also involved in neuronal migration, mitosis, endocytosis, herpes and adenovirus transport, and other basic cellular processes. It has recently been implicated in brain developmental and motor neurodegenerative disease.
A major project in our lab involves the "smooth brain" disease, lissencephaly, which arises from sporadic mutations at the LIS1 locus and resuls from defects in neuronal migration and proliferation during early development. LIS1 functions in the cytoplasmic dynein pathway We have tested the specific effects of reduced expression of LIS1,dynein, and additional regulatory factors by in utero electroporation of embryonic rat brain to express shRNAs and other factors including markers for nuclei, centrosome, and microtubules. We then monitor cellular and subcellular behavior in live brain slices. These studies have led to a model for the role of motor proteins in neuronal migration, and most recently for the long observed interkinetic nuclear oscillations (INM) characteristinc of neuroepithelial and radial glial progenitor cells. We find the unconventional kinesin Kif1a responsible for basal nuclear migration, and cytoplasmic dynein for apical neuronal migration. Current interests include the consequences of kinesin and dynein inhibition for neurogenesis and the relationship between motor activity and cell cycle.
We have also worked out the roles of LIS1 and its interactors NudE and NudEL in cytoplasmic dynein regulation. We find these proteins to function as a triple complex. LIS1 interacts with the dynein motor domain during its power stroke and greatly prolongs this stage of the dynein crossbridge cycle (with S. Gross). The result is a dramatic increase in dynein force production, which we propose to be responsible for the high load forms of transport, such as of nuclei, involved in brain development.
Another interest is in the role of cytoplasmic dynein in neurodegenerative disease. Mutations both in dynein and its accessory complex dynactin cause sensory or motor neuron degeneration. We have succeeded in purifying cytoplasmic dynein from brains of the mutant mouse stain Loa . Despite the location of the mutation in the tail of the dynein molecule, we find a clear defect in motor processivity, a function associated with the dynein motor domains. These results suggest a novel mechanism for long-range allosteric control within cytoplasmic dynein in, and provide molecular insight into the mechanism of neurodegeneration associated with an increasingly important class of mutations.
We are also interested in understanding the role of r dynein and its regulatory proteins in neuritogenesis. With D. Goldberg's lab we have observed cytoplasmic dynein and LIS1 to function within the P-domain of growth cones, using this system to investigate the mechanism by which dynein is recruited to the cell cortex and how it contributes to axonogenesis, polarization, and pathfinding.
Wang, X., Tsai, J.-W., Lian, W.-N, Imai, J. H., Vallee, R. B., and Shi, S.-H. Asymmetric centrosome inheritance maintains neural progenitors in the neocortex. (2009) Nature 461:947-955.
Bremner, K. H., Scherer, J., Yi, J., Vershinin, M., Gross, S. P., and Vallee, R. B. (2009). Adenovirus transport via direct interaction of cytoplasmic dynein with the viral capsid hexon subunit. Cell Host Microbe 6:523-535.
*McKenney, R. J., *Vershinin, M., Kunwar, A., +Vallee R. B., and +Gross, S. P. (2010) LIS1 and NudE induce a persistent dynein force-producing state Cell 141:304-314
*Ori-McKenney, K. M.., *Xu, J., +Gross, S. P., and +Vallee, R. B. (2010) A Cytoplasmic Dynein Tail Mutation Impairs Motor Processivity Nature Cell Biol. 12:1228-1234.
*Tsai, J.-T., *Lian, W.-N., Kemal, S., Kriegstein, A., and Vallee, R. B. (2010) Kinesin 3 and Cytoplasmic Dynein Mediate Interkinetic Nuclear Migration in Neural Stem Cells. Nature Neurosci. 13:1463-1471.