title: Hecate/Grip2a acts to reorganize the cytoskeleton in the symmetry-breaking event of embryonic axis induction.
abstract: Maternal homozygosity for three independent mutant hecate alleles results in embryos with reduced expression of dorsal organizer genes and defects in the formation of dorsoanterior structures. A positional cloning approach identified all hecate mutations as stop codons affecting the same gene, revealing that hecate encodes the Glutamate receptor interacting protein 2a (Grip2a), a protein containing multiple PDZ domains known to interact with membrane-associated factors including components of the Wnt signaling pathway. We find that grip2a mRNA is localized to the vegetal pole of the oocyte and early embryo, and that during egg activation this mRNA shifts to an off-center vegetal position corresponding to the previously proposed teleost cortical rotation. hecate mutants show defects in the alignment and bundling of microtubules at the vegetal cortex, which result in defects in the asymmetric movement of wnt8a mRNA as well as anchoring of the kinesin-associated cargo adaptor Syntabulin. We also find that, although short-range shifts in vegetal signals are affected in hecate mutant embryos, these mutants exhibit normal long-range, animally directed translocation of cortically injected dorsal beads that occurs in lateral regions of the yolk cortex. Furthermore, we show that such animally-directed movement along the lateral cortex is not restricted to a single arc corresponding to the prospective dorsal region, but occur in multiple meridional arcs even in opposite regions of the embryo. Together, our results reveal a role for Grip2a function in the reorganization and bundling of microtubules at the vegetal cortex to mediate a symmetry-breaking short-range shift corresponding to the teleost cortical rotation. The slight asymmetry achieved by this directed process is subsequently amplified by a general cortical animally-directed transport mechanism that is neither dependent on hecate function nor restricted to the prospective dorsal axis.
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Xiaoyan
authors: X
authors: Ge
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Danielle
authors: D
authors: Grotjahn
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Elaine
authors: E
authors: Welch
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Jamie
authors: J
authors: Lyman-Gingerich
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Christiana
authors: C
authors: Holguin
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Eva
authors: E
authors: Dimitrova
authors: Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors: Elliot W
authors: EW
authors: Abrams
authors: Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors: Tripti
authors: T
authors: Gupta
authors: Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors: Florence L
authors: FL
authors: Marlow
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Taijiro
authors: T
authors: Yabe
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Anna
authors: A
authors: Adler
authors: Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors: Mary C
authors: MC
authors: Mullins
authors: Laboratory of Genetics, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
authors: Francisco
authors: F
authors: Pelegri
mesh_terms: D000483:Alleles; D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D003598:Cytoskeletal Proteins / Q000235:genetics; D003599:Cytoskeleton / Q000235:genetics; D004625:Embryo, Nonmammalian; D047108:Embryonic Development / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins / Q000235:genetics; D008870:Microtubules / Q000235:genetics; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism; D054731:PDZ Domains / Q000235:genetics; D010641:Phenotype; D012333:RNA, Messenger / Q000096:biosynthesis; D051153:Wnt Proteins / Q000235:genetics; D014981:Xenopus; D029867:Xenopus Proteins / Q000096:biosynthesis / Q000235:genetics*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; C518827:GRIP2 protein, Xenopus; C000610114:Grip2a protein, zebrafish; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C548373:sybu protein, zebrafish; C094521:wnt8a protein, zebrafish