Joel L Rosenbaum
Professor of Molecular, Cellular, and Developmental Biology
Cilia, flagella, ciliopathies, organelle assembly, Intraflagellar Transport, molecular motors, kinesins and dyneins, sensory cila.
We study flagellar and centriole assembly in the bi-flagellate alga Chlamydomonas, a cell with molecular genetics similar to yeast. Upon deflagellation, over 200 flagellar genes are rapidly upregulated and the resulting flagellar proteins are assembled into large “pre-assembly” complexes in the cytoplasm. These are accumulated at the flagellar basal body/centriole and transported by molecular motors to the distal tip of the flagellum where assembly takes place. The transport occurs by means of multi-polypeptide particles called Intraflagellar Transport “IFT” particles. The IFT particles and motors are also present in the cilia of vertebrate sensory neurons, such as the ones connecting the rod outer and inner segments of the eye, and in the sensory neurons of C elegans. Knockout of IFT genes in the mouse also cause polycystic kidney disease (PKD) and situs inversus. Recent work with the flagella of Chlamydomonas and the sensory cilia of C. elegans indicates that the IFT motility is responsible not only for the movement of structural components of the flagellar/ciliary axoneme to the ciliary tip, but also in the movement of ciliary membrane channels and receptors which are moved along the length of the cilium, in the plane of the ciliary membrane, at the rate of IFT motility. (Qin, Barr and Rosenbaum, In press).