Differential regulation of magnesium transporters Slc41, Cnnm and Trpm6-7 in the kidney of salmonids may represent evolutionary adaptations to high salinity environments.

Magnesium is important for enzymatic reactions and physiological functions, and its intracellular concentration is tightly regulated. Atlantic salmon has the ability to handle large changes in environmental Mg concentration when migrating between freshwater and seawater habitats, making it a relevant model to investigate Mg homeostasis. Parr-smolt transformation (PST) is a life history transition which prepares the freshwater juvenile for the marine environment.

Sulfate homeostasis in Atlantic salmon is associated with differential regulation of salmonid-specific paralogs in gill and kidney.

Sulfate ( ) regulation is challenging for euryhaline species as they deal with large fluctuations of during migratory transitions between freshwater (FW) and seawater (SW), while maintaining a stable plasma concentration. Here, we investigated the regulation and potential role of sulfate transporters in Atlantic salmon during the preparative switch from uptake to secretion. A preparatory increase in kidney and gill sodium/potassium ATPase (Nka) enzyme activity during smolt development indicate preparative osmoregulatory changes.

Phylogenetic Reclassification of Vertebrate Melatonin Receptors To Include Mel1d.

The circadian and seasonal actions of melatonin are mediated by high affinity G-protein coupled receptors (melatonin receptors, MTRs), classified into phylogenetically distinct subtypes based on sequence divergence and pharmacological characteristics. Three vertebrate MTR subtypes are currently described: MT1 (MTNR1A), MT2 (MTNR1B), and Mel1c (MTNR1C / GPR50), which exhibit distinct affinities, tissue distributions and signaling properties. We present phylogenetic and comparative genomic analyses supporting a revised classification of the vertebrate MTR family.

Assembly and positioning of actomyosin rings by contractility and planar cell polarity.

The actomyosin cytoskeleton is a primary force-generating mechanism in morphogenesis, thus a robust spatial control of cytoskeletal positioning is essential. In this report, we demonstrate that actomyosin contractility and planar cell polarity (PCP) interact in post-mitotic Ciona notochord cells to self-assemble and reposition actomyosin rings, which play an essential role for cell elongation. Intriguingly, rings always form at the cells' anterior edge before migrating towards the center as contractility increases, reflecting a novel dynamical property of the cortex.

Regulation by a TGFβ-ROCK-actomyosin axis secures a non-linear lumen expansion that is essential for tubulogenesis.

Regulation of lumen growth is crucial to ensure the correct morphology, dimensions and function of a tubular structure. How this is controlled is still poorly understood. During Ciona intestinalis notochord tubulogenesis, single extracellular lumen pockets grow between pairs of cells and eventually fuse into a continuous tube.

An adhesome comprising laminin, dystroglycan and myosin IIA is required during notochord development in Xenopus laevis.

Dystroglycan (Dg) is a transmembrane receptor for laminin that must be expressed at the right time and place in order to be involved in notochord morphogenesis. The function of Dg was examined in Xenopus laevis embryos by knockdown of Dg and overexpression and replacement of the endogenous Dg with a mutated form of the protein. This analysis revealed that Dg is required for correct laminin assembly, for cell polarization during mediolateral intercalation and for proper differentiation of vacuoles.

An equatorial contractile mechanism drives cell elongation but not cell division.

Cell shape changes and proliferation are two fundamental strategies for morphogenesis in animal development. During embryogenesis of the simple chordate Ciona intestinalis, elongation of individual notochord cells constitutes a crucial stage of notochord growth, which contributes to the establishment of the larval body plan. The mechanism of cell elongation is elusive.

Tubulogenesis in a simple cell cord requires the formation of bi-apical cells through two discrete Par domains.

Apico-basal polarization is a crucial step in the de novo formation of biological tubes. In Ciona notochord, tubulogenesis occurs in a single file of cells in the absence of cell proliferation. This configuration presents a unique challenge for the formation of a continuous lumen.

Ciona intestinalis notochord as a new model to investigate the cellular and molecular mechanisms of tubulogenesis.

Biological tubes are a prevalent structural design across living organisms. They provide essential functions during the development and adult life of an organism. Increasing progress has been made recently in delineating the cellular and molecular mechanisms underlying tubulogenesis.

Tube formation by complex cellular processes in Ciona intestinalis notochord.

In the course of embryogenesis multicellular structures and organs are assembled from constituent cells. One structural component common to many organs is the tube, which consists most simply of a luminal space surrounded by a single layer of epithelial cells. The notochord of ascidian Ciona forms a tube consisting of only 40 cells, and serves as a hydrostatic "skeleton" essential for swimming.

Are Hox genes ancestrally involved in axial patterning? Evidence from the hydrozoan Clytia hemisphaerica (Cnidaria).

Background: The early evolution and diversification of Hox-related genes in eumetazoans has been the subject of conflicting hypotheses concerning the evolutionary conservation of their role in axial patterning and the pre-bilaterian origin of the Hox and ParaHox clusters. The diversification of Hox/ParaHox genes clearly predates the origin of bilaterians. However, the existence of a "Hox code" predating the cnidarian-bilaterian ancestor and supporting the deep homology of axes is more controversial.

Acetylcholinesterase activity in Clytia hemisphaerica (Cnidaria).

Cholinesterase activity is known in representatives of all living organisms phyla but the origin of the cholinergic system as known in bilaterian animals is still undeciphered. In particular the implication of cholinesterases in the nervous system of non-bilaterian Metazoa is not well known. We thus chose to investigate this activity in the Clytia hemisphaerica (Cnidaria) medusa.

A function for dystroglycan in pronephros development in Xenopus laevis.

Dystroglycan (Dg) is a laminin receptor that is expressed at the interface between the basement membrane and the cell membrane. Dg has been reported to play a role in skeletal muscle cell stability, morphogenesis of neuroepithelial tissues, and in regulating cytoskeletal organization, cell polarization, and cell signalling. In this study, we have focused our analysis on the expression of Dg-mRNA and protein at different developmental stages in the pronephros of Xenopus laevis.

Ordered progression of nematogenesis from stem cells through differentiation stages in the tentacle bulb of Clytia hemisphaerica (Hydrozoa, Cnidaria).

Nematogenesis, the production of stinging cells (nematocytes) in Cnidaria, can be considered as a model neurogenic process. Most molecular data concern the freshwater polyp Hydra, in which nematocyte production is scattered throughout the body column ectoderm, the mature cells then migrating to the tentacles. We have characterized tentacular nematogenesis in the Clytia hemisphaerica hydromedusa and found it to be confined to the ectoderm of the tentacle bulb, a specialized swelling at the tentacle base.