title: Drosophila klaroid encodes a SUN domain protein required for Klarsicht localization to the nuclear envelope and nuclear migration in the eye.
abstract: KASH (Klarsicht/Anc-1/Syne homology) domain proteins are cytoskeleton-associated proteins localized uniquely to the outer nuclear membrane. Klarsicht is a KASH protein required for nuclear migration in differentiating cells of the Drosophila eye. The C-terminal KASH domain of Klarsicht resides in the perinuclear space, and the cytoplasmic moiety connects to the microtubule organizing center. In C. elegans and vertebrate cells, SUN (Sad1/UNC-84) domain proteins reside in the inner nuclear membrane and tether KASH proteins to the outer nuclear membrane. Is there a Drosophila SUN protein that performs a similar function, and if so, is it like Klarsicht, obviously essential for nuclear positioning only in the eye? Here, we identify Drosophila Klaroid, a SUN protein that tethers Klarsicht. klaroid loss-of-function mutants are indistinguishable phenotypically from klarsicht mutants. Remarkably, neither gene is essential for Drosophila viability or fertility, and even in klaroid klorsicht double mutants, the only obvious external morphological defect is rough eyes. In addition, we find that klaroid and klarsicht are required for nuclear migration in differentiating neurons and in non-neural cells. Finally, while perinuclear Klaroid is ubiquitous in the eye, Klarsicht expression is limited to differentiating cells and may be part of the trigger for apical nuclear migration.
authors.affiliation: Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, 78712, USA.
authors.forename: Martin P
authors.initials: MP
authors.lastname: Kracklauer
authors.forename: Susan M L
authors.initials: SM
authors.lastname: Banks
authors.forename: Xuanhua
authors.initials: X
authors.lastname: Xie
authors.forename: Yaning
authors.initials: Y
authors.lastname: Wu
authors.forename: Janice A
authors.initials: JA
authors.lastname: Fischer
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development*; D005123:Eye / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009685:Nuclear Envelope / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D005136:Eye Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C401521:klar protein, Drosophila; C554441:koi protein, Drosophila