Molecular analysis of the klarsicht gene and its role in nuclear migration within differentiating cells of the Drosophila eye.
BACKGROUND
The temporally regulated, cell-type-specific transport of organelles has great biological significance, yet little is known about the regulation of organelle transport during development. The Drosophila gene klarsicht is required for temporally regulated lipid droplet transport in developing embryos and for the stereotypical nuclear migrations in differentiating cells of the developing eye. Klarsicht is thought to coordinate the function of several molecular motors bound to a single lipid droplet or to facilitate the attachment of dynein to the cargo, but it is not known whether Klarsicht affects motors directly or indirectly.


RESULTS
Here, we have cloned the klarsicht gene and shown that it encodes a unique large protein. Drosophila klarsicht null mutants were viable, with obvious defects only in adult eye morphology. Epitope-tagged Klarsicht expressed in the eye from a transgene was perinuclear. In flies carrying transgenes that express markers for microtubule plus and minus ends, microtubules in differentiating cells of the eye were oriented with their plus ends apical and their minus ends at the nucleus.


CONCLUSIONS
Drosophila klarsicht null mutants were viable and fertile, demonstrating that klarsicht is essential only for specific motor protein functions. Perinuclear localization of Klarsicht protein indicates that Klarsicht has a direct mechanical role in nuclear migration. Taken together with the finding that the minus ends of the microtubules are associated with the photoreceptor nuclei, the observation that Klarsicht is largely perinuclear supports the idea that Klarsicht associates with dynein, consistent with a model in which Klarsicht assists dynein in 'reeling in' the nucleus.
Mosley-Bishop
K L
KL
Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Moffett Molecular Biology Building, 2500 Speedway, Austin, Texas 78712, USA.
Li
Q
Q
Patterson
L
L
Fischer
J A
JA
D000818:Animals; D001692:Biological Transport; D002454:Cell Differentiation / Q000235:genetics; D002467:Cell Nucleus / Q000502:physiology; D003001:Cloning, Molecular; D004330:Drosophila / Q000166:cytology / Q000235:genetics*; D029721:Drosophila Proteins; D018014:Gene Transfer Techniques; D019476:Insect Proteins / Q000235:genetics*; D026901:Membrane Transport Proteins; D008870:Microtubules / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology*; D013347:Subcellular Fractions
D029721:Drosophila Proteins; D019476:Insect Proteins; D026901:Membrane Transport Proteins; C401521:klar protein, Drosophila