students reading in hallway

Faculty and Staff


Michael Tibbetts Associate Professor of Biology

Contact:
Office: Reem-Kayden Center 212
Phone: 845-752-2309
E-mail: tibbetts@bard.edu
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Education

Ph.D., Molecular Biology and Biochemistry (1989), Wesleyan University
B.S., Biology (1983), University of Massachussets, Dartmouth

Courses

Biology 101, Biological Inquiry; Biology 151, Genes to TraitsBiology 201, Eukaryotic Genetics; Biology 302, Molecular Biology; Biology 304, Cell Biology; Biology 411, Cancer Biology.

Research


We hear sounds because pressure waves in the air cause the eardrum to oscillate.  These oscillations are transferred to the inner ear structure, the cochlea by the three tiny bones in the middle ear - the hammer, anvil, and stirrup.  The movement of these bones cause the basilar membrane in the cochlea to vibrate in a frequency specific manner.  The vibrations of the basilar membrane lead to the deflection of stereocilia on specialized cells, called hair cells.  It is the deflection of the stereocilia of hair cells that leads to the electrical response that is transmitted to the brain and interpreted as sound of a prticular frequency.  

Zebrafish, have hair cells contained within
specialized structures of the lateral line system called neuromasts, that are remarkably similar in structure and function to our cochlear hair cells in.  These hair cells relay signals of both intensity and direction of water movement to the brain, making the fish exquisitely sensitive to movement by predators and prey.  In order to relay directional information, each hair cell must maintain a particular orientation within the neuromast.  each cell responds to water movement in only one direction and transmits the signal to the appropriate neuron within the brain.  Interestingly, the hair cells within the lateral line of fish, unlike the hair cells in our inner ears, have the capacity to regenerate.

My lab is interested in two questions relating to hair cells in the lateral line of zebrafish. First, what are the mechanisms that maintain hair cell orientation.  Hair cells need to change positions within the neuromast to fill in where old cells have died and to accommodate the formation of new ones.  How do these cells reorient themselves after having moved?  Second, evidence from specific mutant zebrafish and from chemical interference studies suggest that the mechanism by which hair cells regenerate is distinct from the mechanism by which they first form during development.  In the phoenix mutant, neuromasts and hair cells develop normally.  However, after ablation of hair cells in fully developed neuromasts, new hair cells are generated at a much slower rate than in wild type zebrafish larvae (1).

Using genetic and pharmacological interventions, my lab is asking which proteins and which cellular processes are important for each of these phenomena.

1.  Behra M, Bradsher J, Sougrat R, Gallardo V, Allende ML, Burgess SM. Phoenix is required for mechanosensory hair cell regeneration in the zebrafish lateral line. PLoS Genet. 2009 Apr;5(4):e1000455.