Tissue-specific expression of Sarcoplasmic/Endoplasmic Reticulum Calcium ATPases (ATP2A/SERCA) 1, 2, 3 during Xenopus laevis development

Cardiac contractility of the African sharptooth catfish, Clarias gariepinus: role of extracellular Ca2+, sarcoplasmic reticulum, and β-adrenergic stimulation

This study investigated the dependence of contraction from extracellular Ca²⁺, the presence of a functional sarcoplasmic reticulum (SR), and the effects of β-adrenergic stimulation using isometric cardiac muscle preparations. Moreover, the expression of Ca²⁺-handling proteins such as SR-Ca²⁺-ATPase (SERCA), phospholamban (PLN), and Na⁺/Ca²⁺ exchanger (NCX) were also evaluated in the ventricular tissue of adult African sharptooth catfish, Clarias gariepinus, a facultative air-breathing fish. In summary, we observed that (1) contractility was strongly regulated by extracellular Ca²⁺; (2) inhibition of SR Ca²⁺-release by application of ryanodine reduced steady-state force production; (3) ventricular myocardium exhibited clear post-rest decay, even in the presence of ryanodine, indicating a decrease in SR Ca²⁺ content and NCX as the main pathway for Ca²⁺ extrusion; (4) a positive force-frequency relationship was observed above 60 bpm (1.0 Hz); (5) ventricular tissue was responsive to β-adrenergic stimulation, which caused significant increases in twitch force, kept a linear force-frequency relationship from 12 to 96 bpm (0.2 to Hz), and improved the cardiac pumping capacity (CPC); and (6) African catfish myocardium exhibited similar expression patterns of NCX, SERCA, and PLN, corroborating our findings that both mechanisms for Ca²⁺ transport across the SR and sarcolemma contribute to Ca²⁺ activator. In conclusion, this fish species displays great physiological plasticity of E-C coupling, able to improve the ability to maintain cardiac performance under physiological conditions to ecological and/or adverse environmental conditions, such as hypoxic air-breathing activity.

An Indo-Pacific Humpback Dolphin Genome Reveals Insights into Chromosome Evolution and the Demography of a Vulnerable Species

The Indo-Pacific humpback dolphin (Sousa chinensis) is a small inshore species of odontocete cetacean listed as Vulnerable on the IUCN Red List. Here, we report on the evolution of S. chinensis chromosomes from its cetruminant ancestor and elucidate the evolutionary history and population genetics of two neighboring S. chinensis populations. We found that breakpoints in ancestral chromosomes leading to S. chinensis could have affected the function of genes related to kidney filtration, body development, and immunity. Resequencing of individuals from two neighboring populations in the northwestern South China Sea, Leizhou Bay and Sanniang Bay, revealed genetic differentiation, low diversity, and small contemporary effective population sizes. Demographic analyses showed a marked decrease in the population size of the two investigated populations over the last ~4,000 years, possibly related to climatic oscillations. This study implies a high risk of extinction and strong conservation requirement for the Indo-Pacific humpback dolphin.

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Deducing chromosome evolution from ancestral Cetruminantia and ancestral Odontoceti

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Reconstructing the demographic history of Sousa chinensis

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Implying high risk of extinction and strong conservation requirement for S. chinensis

An atlas of Wnt activity during embryogenesis in Xenopus tropicalis

Wnt proteins form a family of highly conserved secreted molecules that are critical mediators of cell-cell signaling during embryogenesis. Partial data on Wnt activity in different tissues and at different stages have been reported in frog embryos. Our objective here is to provide a coherent and detailed description of Wnt activity throughout embryo development. Using a transgenic Xenopus tropicalis line carrying a Wnt-responsive reporter sequence, we depict the spatial and temporal dynamics of canonical Wnt activity during embryogenesis. We provide a comprehensive series of in situ hybridization in whole-mount embryos and in cross-sections, from gastrula to tadpole stages, with special focus on neural tube, retina and neural crest cell development. This collection of patterns will thus constitute a valuable resource for developmental biologists to picture the dynamics of Wnt activity during development.

Maternal and embryonic exposure to the water soluble fraction of crude oil or lead induces behavioral abnormalities in zebrafish (Danio rerio), and the mechanisms involved

The water-soluble fraction (WSF) of crude oil plays an important role in the toxicity of crude oil in aquatic environments. Heavy metals, such as lead (Pb) are also important environmental contaminants, which can reach aquatic systems via the effluents of industrial, urban and mining sources. In the present study, we investigated whether maternal and embryonic exposure to the WSF (5, 50 μg/L) or Pb (10, 100 μg/L) could induce behavioral abnormalities in zebrafish. Our results showed that maternal and embryonic exposure to the WSF (5, 50 μg/L) and Pb (10, 100 μg/L) induced swimming activity alterations in larval and juvenile zebrafish. In 15 days post-fertilization (dpf) larval zebrafish, the distance moved was significantly increased in the groups treated with the WSF (5, 50 μg/L), but the angular velocity and turn angle were decreased after treatment with the WSF (5, 50 μg/L) or Pb (10, 100 μg/L). In 30 dpf juvenile zebrafish, the distance moved was markedly decreased in both groups treated with the WSF (5, 50 μg/L) and the Pb (10 μg/L) group, but the percentage of zebrafish moving up and the inter-fish distance of two juvenile fish were increased after treatment with the WSF (5, 50 μg/L) or Pb (10, 100 μg/L). Maternal and embryonic exposure to the WSF (5, 50 μg/L) or Pb (10, 100 μg/L) likely impaired the brain neurons growth and induced behavioral abnormalities in the larval and juvenile zebrafish. Furthermore, the expressions of some key genes, which were associated with calcium channels, behavioral development or the metabolism of environmental contaminants, were changed.

Crude oil exposures reveal roles for intracellular calcium cycling in haddock craniofacial and cardiac development

Recent studies have shown that crude oil exposure affects cardiac development in fish by disrupting excitation-contraction (EC) coupling. We previously found that eggs of Atlantic haddock (Melanogrammus aeglefinus) bind dispersed oil droplets, potentially leading to more profound toxic effects from uptake of polycyclic aromatic hydrocarbons (PAHs). Using lower concentrations of dispersed crude oil (0.7-7 μg/L ∑PAH), here we exposed a broader range of developmental stages over both short and prolonged durations. We quantified effects on cardiac function and morphogenesis, characterized novel craniofacial defects, and examined the expression of genes encoding potential targets underlying cardiac and craniofacial defects. Because of oil droplet binding, a 24-hr exposure was sufficient to create severe cardiac and craniofacial abnormalities. The specific nature of the craniofacial abnormalities suggests that crude oil may target common craniofacial and cardiac precursor cells either directly or indirectly by affecting ion channels and intracellular calcium in particular. Furthermore, down-regulation of genes encoding specific components of the EC coupling machinery suggests that crude oil disrupts excitation-transcription coupling or normal feedback regulation of ion channels blocked by PAHs. These data support a unifying hypothesis whereby depletion of intracellular calcium pools by crude oil-derived PAHs disrupts several pathways critical for organogenesis in fish.

IP3R, store-operated Ca2+ entry and neuronal Ca2+ homoeostasis in Drosophila

The IP3R (inositol 1,4,5-trisphosphate receptor) releases Ca2+ from the ER (endoplasmic reticulum) store upon binding to its ligand InsP3, which is thought to be generated by activation of certain membrane-bound G-protein-coupled receptors in Drosophila. Depletion of Ca2+ in the ER store also activates SOCE (store-operated Ca2+ entry) from the extracellular milieu across the plasma membrane, leading to a second rise in cytosolic Ca2+, which is then pumped back into the ER. The role of the IP3R and SOCE in mediating Ca2+ homoeostasis in neurons, their requirement in neuronal function and effect on neuronal physiology and as a consequence behaviour, are reviewed in the present article.

Two distinct calcium pools in the endoplasmic reticulum of HEK-293T cells

Agonist-sensitive intracellular Ca2+ stores may be heterogeneous and exhibit distinct functional features. We have studied the properties of intracellular Ca2+ stores using targeted aequorins for selective measurements in different subcellular compartments. Both, HEK-293T [HEK (human embryonic kidney)-293 cells expressing the large T-antigen of SV40 (simian virus 40)] and HeLa cells accumulated Ca2+ into the ER (endoplasmic reticulum) to near millimolar concentrations and the IP3-generating agonists, carbachol and ATP, mobilized this Ca2+ pool. We find in HEK-293T, but not in HeLa cells, a distinct agonist-releasable Ca2+ pool insensitive to the SERCA (sarco/endoplasmic reticulum Ca2+ ATPase) inhibitor TBH [2,5-di-(t-butyl)-benzohydroquinone]. TG (thapsigargin) and CPA (cyclopiazonic acid) completely emptied this pool, whereas lysosomal disruption or manoeuvres collapsing endomembrane pH gradients did not. Our results indicate that SERCA3d is important for filling the TBH-resistant store as: (i) SERCA3d is more abundant in HEK-293T than in HeLa cells; (ii) the SERCA 3 ATPase activity of HEK-293T cells is not fully blocked by TBH; and (iii) the expression of SERCA3d in HeLa cells generated a TBH-resistant agonist-mobilizable compartment in the ER. Therefore the distribution of SERCA isoforms may originate the heterogeneity of the ER Ca2+ stores and this may be the basis for store specialization in diverse functions. This adds to recent evidence indicating that SERCA3 isoforms may subserve important physiological and pathophysiological mechanisms.