Tama Hasson
Assistant Professor of Biology, UCSD

e-mail: tama@biomail.ucsd.edu

      My laboratory studies molecular motors, proteins that use ATP hydrolysis to drive directed movement along cytoskeletal filaments within each cell. Specifically, we study myosins, a large family of proteins which move along actin filaments. Myosins have been implicated in a variety of actin-based cell processes including cytokinesis, cell migration, and membrane trafficking and also appear to be intricately involved in the cell-signalling pathways that regulate the assembly of the actin cytoskeleton. The myosin family has been divided into fifteen distinct classes, of which fourteen are termed unconventional myosin classes. My laboratory studies proteins from two of these unconventional myosin classes, myosin-VI and myosin-VIIa.

      Myosin-VI and myosin-VIIa were cloned as part of a project to identify new unconventional myosins expressed by polarized epithelial cells (1,2).  Unexpectedly, both myosin-VI and myosin-VIIa were subsequently found to encode deafness genes (3,4). Both myosin-VI and myosin-VIIa are expressed exclusively by the hair cells, the sensory cells of the inner ear. Within these cells, myosin-VI and myosin-VIIa are associated with different subdomains of the stereocilia, the polarized actin bundles that act in the transduction process (5). As shown in the figures, myosin-VIIa is located along the length of the stereocilia, whereas myosin-VI is found at the base of the stereocilia. This difference in location between class VI and class VII myosins is recapitulated in other tissues, allowing us to study myosin targeting and enzymology in a variety of cell types and systems.

     My laboratory will focus on the enzymatic characterization of Class VI and Class VII myosins and the identification of their protein and/or membrane cargo. This work will utilize a number of different approaches, including cell biology, biochemistry, genetic and molecular biology techniques, to ascertain the functions of myosin in the inner ear and in other tissues.

To learn more about recent work on myosin-VI, visit the Myosin Web Page at:
http://blocks.fhcrc.org/~myosin/Myo6.html

     (1) Hasson T. (1997) Unconventional myosins, the basis for deafness inmouse and man. Am. J. Hum.Genet. 61: 801-805.

     (2) Hasson T, Gillespie PG, Garcia JA, MacDonald RB, Zhao Y-D, Yee AG,Mooseker MS, Corey, DP (1997) Unconventional myosins in inner-ear sensoryepithelia. J. Cell Biol. 137: 1287-1307. 

     (3) Hasson T, Heintzelman MB, Santos-Sacchi J, Corey DP, Mooseker MS(1995) Expression in cochlea and retina of myosin VIIa, the gene productdefective in Usher syndrome type 1B. Proc. Natl. Acad. Sci. USA 92: 9815-9819. 

     (4) Avraham KB, Hasson T, Steel KP, Kingsley DM, Russell LB, Mooseker MS,Copeland NG, Jenkins, NA (1995) The mouse Snell's waltzer deafness geneencodes an unconventional myosin required for structural integrity ofinner hair cells. Nature Genet. 11: 369-374. 

     (5) Hasson T, Mooseker MS (1994) Porcine myosin-VI: Characterization of anew mammalian unconventional myosin. J. Cell Biol. 127: 425-440. 

Tama Hasson received her Ph.D. from Princeton University and completed postdoctoral training at Yale.