Cytoplasmic dynein has long been thought to be responsible for retrograde axonal transport. As the number of cellular roles for this multifunctional protein has expanded, the complexity of its contribution to axonal transport has increased. In this article the increasing evidence for a role for cytoplasmic dynein in anterograde as well as retrograde transport is discussed. The current status of the complex dynein cargo-binding mechanism is evaluated. Finally, recent genetic evidence supporting a role in axonal transport and revealing a role in neurodegenerative conditions is reviewed.

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NMR spectroscopy is a powerful approach for quantitating molecular conformational dynamics at multiple atomic sites and over multiple time scales. Extensive studies by solution and solid-state NMR spectroscopy of spin relaxation and line shapes in biological macromolecules have been performed in order to characterize the amplitudes, time scales, and energetics of intramolecular conformational modes and to elucidate the relationships between conformational dynamics, structure, and function. This review describes NMR spectroscopic methods for investigation of conformational dynamics together with theoretical descriptions appropriate for interpretation and simulation of the techniques, surveys the range of results available from solution and solid state NMR studies of proteins and other biomolecules, and identifies opportunities for further individual and collaborative development of solution and solid state NMR techniques for characterizing the dynamical properties of biological macromolecules.

Incomplete retinal vascularization occurs in both Norrie disease and familial exudative vitreoretinopathy (FEVR). Norrin, the protein product of the Norrie disease gene, is a secreted protein of unknown biochemical function. One form of FEVR is caused by defects in Frizzled-4 (Fz4), a presumptive Wnt receptor. We show here that Norrin and Fz4 function as a ligand-receptor pair based on (1) the similarity in vascular phenotypes caused by Norrin and Fz4 mutations in humans and mice, (2) the specificity and high affinity of Norrin-Fz4 binding, (3) the high efficiency with which Norrin induces Fz4- and Lrp-dependent activation of the classical Wnt pathway, and (4) the signaling defects displayed by disease-associated variants of Norrin and Fz4. These data define a Norrin-Fz4 signaling system that plays a central role in vascular development in the eye and ear, and they indicate that ligands unrelated to Wnts can act through Fz receptors.