Subject(s)
Cilia/ultrastructure , Models, Biological , Morphogenesis/physiology , Transcription Factors , Animals , Calcium Signaling , Chick Embryo , Ciliary Motility Disorders/embryology , Embryo, Mammalian/ultrastructure , Gene Expression Regulation, Developmental , Humans , Kinesins/deficiency , Kinesins/genetics , Kinesins/physiology , Left-Right Determination Factors , Mechanoreceptors/physiology , Membrane Potentials , Membrane Proteins/deficiency , Membrane Proteins/genetics , Membrane Proteins/physiology , Mice , Morphogenesis/genetics , Nodal Protein , Organizers, Embryonic/ultrastructure , Proteins/genetics , Proteins/physiology , Rheology , Situs Inversus/embryology , TRPP Cation Channels , Transforming Growth Factor beta/deficiency , Transforming Growth Factor beta/genetics , Transforming Growth Factor beta/physiologyABSTRACT
How left right handedness originates in the body plan of the developing vertebrate embryo is a subject of considerable debate. In mice, a left right bias is thought to arise from a directional extracellular flow (nodal flow) that is generated by dynein-dependent rotation of monocilia on the ventral surface of the embryonic node. Here we show that the existence of node monocilia and the expression of a dynein gene that is implicated in ciliary function are conserved across a wide range of vertebrate classes, indicating that a similar ciliary mechanism may underlie the establishment of handedness in all vertebrates.
Subject(s)
Body Patterning , Cilia/physiology , Dyneins/metabolism , Embryo, Mammalian/cytology , Embryo, Mammalian/embryology , Embryo, Nonmammalian , Vertebrates/embryology , Animals , Axonemal Dyneins , Chick Embryo , Conserved Sequence , Dyneins/genetics , Embryo, Mammalian/metabolism , Gastrula/cytology , Gastrula/metabolism , Gene Expression Profiling , Gene Expression Regulation, Developmental , Mice , Organizers, Embryonic/embryology , Organizers, Embryonic/metabolism , Signal Transduction , Vertebrates/genetics , Xenopus/embryology , Xenopus/genetics , Zebrafish/embryology , Zebrafish/genetics , Zebrafish ProteinsABSTRACT
All vertebrates have a left-right body axis with invariant asymmetries of the heart and the positions of the abdominal viscera. Major advances have recently been made in defining molecular components of the pathway specifying the vertebrate left-right axis, but our knowledge of the early determinants is extremely limited. In the invmouse the left-right axis is consistently reversed, unlike other vertebrate mutants where randomisation of situs is apparent. The gene disrupted in this mouse encodes a 1062-amino-acid protein, inversin. We previously reported 16 tandem ankyrin repeats, spanning amino acids 13-557, and two putative nuclear localisation sequences, but otherwise the sequence offered few clues to the possible function. In order to identify regions likely to be functionally important, we have identified and characterised orthologous sequences in several species, including chick, Xenopus and zebrafish. Sequence comparisons show strong conservation of the ankyrin repeat region and also a lysine-rich domain spanning amino acids 558-604. Further analysis identified a highly conserved IQ calmodulin-binding domain in the latter region and another such domain in an otherwise poorly conserved C-terminal region. A yeast two-hybrid screen identified calmodulin in one third of the positive clones, and we confirmed this interaction by immunoprecipitation.
