A Conserved Role of the Unconventional Myosin 1d in Laterality Determination
Authors: Tingler, Melanie; Kurz, Sabrina; Maerker, Markus; Ott, Tim; Fuhl, Franziska; Schweickert, Axel; LeBlanc-Straceski, Janine M.; Noselli, Stephane; Blum, Martin
Anatomical and functional asymmetries are widespread in the animal kingdom [1,2]. In vertebrates, many visceral organs are asymmetrically placed . In snails,shells and inner organs coil asymmetrically, and in Drosophila,genitalia and hindgut undergo a chiral rotation during development. The evolutionary origin of these asymmetries remains an open question . Nodal signaling is widely used ,and many,but not all,vertebrates use cilia for symmetry breaking . In Drosophila, which lacks both cilia and Nodal,the unconventional myosin ID (myo1d) gene controls dextral rotation of chiral organs [6,7]. Here,we studied the role of myo1d in left-right (LR) axis formation in Xenopus. Morpholino oligomer-mediated myo1d downregulation affected organ placement in >50% of morphant tadpoles. Induction of the left-asymmetric Nodal cascade was aberrant in >70% of cases. Expression of the flow-target gene dand5 was compromised,as was flow itself,due to shorter,fewer,and non-polarized cilia at the LR organizer. Additional phenotypes pinpointed Wnt/planar cell polarity signaling and suggested that myo1d,like in Drosophila ,acted in the context of the planar cell polarity pathway. Indeed,convergent extension of gastrula explant cultures was inhibited in myo1d morphants,and the ATF2 reporter gene for non-canonical Wnt signaling was downregulated. Finally,genetic interference experiments demonstrated a functional interaction between the core planar cell polarity signaling gene vangl2 and myo1d in LR axis formation. Thus,our data identified myo1d as a common denominator of arthropod and chordate asymmetry, in agreement with a monophyletic origin of animal asymmetry.
Identification and expression analysis of BMP signaling inhibitors genes of the DAN family in amphioxus
GENE EXPRESSION PATTERNS
Authors: Le Petillon, Yann; Oulion, Silvan; Escande, Marie-Line; Escriva, Hector; Bertrand, Stephanie
Bone morphogenetic proteins (BMPs) are members of the Transforming Growth Factor-beta (TGF-beta family implicated in many developmental processes in metazoans such as embryo axes specification. Their wide variety of actions is in part controlled by inhibitors that impede the interaction of BMPs with their specific receptors. Here, we focused our attention on the Differential screening-selected gene Aberrative in Neuroblastoma (DAN) family of inhibitors. Although they are well-characterized in vertebrates, few data are available for this family in other metazoan species. In order to understand the evolution of potential developmental roles of these inhibitors in chordates, we identified the members of this family in the cephalochordate amphioxus, and characterized their expression patterns during embryonic development. Our data suggest that the function of Cerberus/Dand5 subfamily genes is conserved among chordates, whereas Gremlin1/2 and NBL1 subfamily genes seem to have acquired divergent expression patterns in each chordate lineage. On the other hand, the expression of Gremlin in the amphioxus neural plate border during early neurulation strengthens the hypothesis of a conserved neural plate border gene network in chordates. (C) 2013 Elsevier B.V. All rights reserved.