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A tumor suppressor Retinoblastoma1 is essential for embryonic development in the sea urchin.

Latest Publications - 12 hours 51 min ago
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A tumor suppressor Retinoblastoma1 is essential for embryonic development in the sea urchin.

Dev Dyn. 2019 12;248(12):1273-1285

Authors: Fernandez-Nicolas A, Xu D, Yajima M

Abstract
BACKGROUND: Embryonic cells and cancer cells share various cellular characteristics important for their functions. It has been thus proposed that similar mechanisms of regulation may be present in these otherwise disparate cell types.
RESULTS: To explore how regulative embryonic cells are fundamentally different from cancerous cells, we report here that a fine balance of a tumor suppressor protein Retinoblastoma1 (Rb1) and a germline factor Vasa are important for proper cell proliferation and differentiation of the somatic cells during embryogenesis of the sea urchin. Rb1 knockdown blocked embryonic development and induced Vasa accumulation in the entire embryo, while its overexpression resulted in a smaller-sized embryo with differentiated body structures. These results suggest that a titrated level of Rb1 protein may be essential for a proper balance of cell proliferation and differentiation during development. Vasa knockdown or overexpression, on the other hand, reduced or increased Rb1 protein expression, respectively.
CONCLUSIONS: Taken together, it appears that Vasa protein positively regulates Rb1 protein while Rb1 protein negatively regulates Vasa protein, balancing the act of these two antagonistic molecules in somatic cells. This mechanism may provide a fine control of cell proliferation and differentiation, which is essential for regulative embryonic development.

PMID: 31515896 [PubMed - indexed for MEDLINE]

Categories: pubmed

Inhibitory effects of neurotoxin β-N-methylamino-L-alanine on fertilization and early development of the sea urchin Lytechinus pictus.

Latest Publications - Wed, 05/13/2020 - 01:12
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Inhibitory effects of neurotoxin β-N-methylamino-L-alanine on fertilization and early development of the sea urchin Lytechinus pictus.

Aquat Toxicol. 2020 Apr;221:105425

Authors: Li A, Espinoza J, Hamdoun A

Abstract
Neurotoxin β-N-methylamino-L-alanine (BMAA) has been widely detected in diverse aquatic organisms and hypothesized as an environmental risk to neurodegenerative diseases in humans. However, the knowledge of its toxicity to marine organisms requires attention. In the present study, embryos and sperm of the sea urchin, Lytechinus pictus, were used to assess the toxicity of BMAA. Effects of BMAA on fertilization and development of sea urchin embryos were measured, and its impacts on efflux transport of sea urchin blastula were also assayed. Results demonstrated that the fertilization and development of embryos were significantly inhibited by high concentrations of BMAA above 300 μg L-1. The EC50 values indicated by active swimming larvae and total larvae numbers at 96 HPF (hours post fertilization) were 165 μg L-1 (1.4 μmol L-1) and 329 μg L-1 (2.8 μmol L-1), respectively. Additionally, sperm exposed to BMAA for 10 min significantly reduced the fertilization ratio of sea urchin eggs. However, the ABC transport activity on the cytomembrane of sea urchin blastula was not inhibited by the presence of BMAA at 50 μg L-1, even up to 500 μg L-1. Abnormal division and developmental malformations occurred at different developmental stages for sea urchin embryos exposed to BMAA at 500 μg L-1. The inhibitory effects of BMAA on sea urchin embryos were reported at the first time in this study, for which the toxicological mechanisms will be explored in future studies.

PMID: 32058875 [PubMed - indexed for MEDLINE]

Categories: pubmed

Sea urchins mediate the availability of kelp detritus to benthic consumers.

Latest Publications - Wed, 05/13/2020 - 01:12
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Sea urchins mediate the availability of kelp detritus to benthic consumers.

Proc Biol Sci. 2019 07 10;286(1906):20190846

Authors: Yorke CE, Page HM, Miller RJ

Abstract
Detritus can fundamentally shape and sustain food webs, and shredders can facilitate its availability. Most of the biomass of the highly productive giant kelp, Macrocystis pyrifera, becomes detritus that is exported or falls to the seafloor as litter. We hypothesized that sea urchins process kelp litter through shredding, sloppy feeding and egestion, making kelp litter more available to benthic consumers. To test this, we conducted a mesocosm experiment in which an array of kelp forest benthic consumers were exposed to 13C- and 15N-labelled Macrocystis with or without the presence of sea urchins, Strongylocentrotus purpuratus. Our results showed that several detritivore species consumed significant amounts of kelp, but only when urchins were present. Although they are typically portrayed as antagonistic grazers in kelp forests, sea urchins can have a positive trophic role, capturing kelp litter before it is exported and making it available to a suite of benthic detritivores.

PMID: 31288702 [PubMed - indexed for MEDLINE]

Categories: pubmed

The role of fasting on spine regeneration and bacteremia in the purple sea urchin Strongylocentrotus purpuratus.

Latest Publications - Thu, 05/07/2020 - 00:57
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The role of fasting on spine regeneration and bacteremia in the purple sea urchin Strongylocentrotus purpuratus.

PLoS One. 2020;15(2):e0228711

Authors: Scholnick DA, Winslow AE

Abstract
Fasting has been shown to increase longevity and alter immune function in a variety of animals, but little is understood about how reduced caloric intake may impact regeneration and infections in animals that must regularly repair and regenerate tissue in marine environments that contain high levels of bacteria. We examined the possibility that fasting could enhance spine regeneration and reduce bacteremia in the purple sea urchin Strongylocentrotus purpuratus. A small number of spines were removed from urchins and rates of spine regrowth and levels of culturable bacteria from the coelomic fluid were measured for 21 days in fed and fasted urchins. Fasted urchins had higher rates of spine regrowth and lower levels of colony-forming units (CFU) per milliliter of coeolomic fluid. The predominant bacteria in the coelomic fluid was isolated and identified by DNA sequence-based methods as Vibrio cyclitrophicus. After 21 days, fasted and fed urchins were injected with V. cyclitrophicus. Two hours after injection, fed urchins had about 25% more culturable bacteria remaining in their coelomic fluid compared to fasted urchins. We found no evidence that fasting altered coelomic fluid cell number or righting response, indicators of physiologic and behavioral stress in urchins. Our results demonstrate that V. cyclitrophicus is present in purple urchin coelomic fluid, that fasting can increase spine regeneration and that fasted urchins have much lower levels of culturable bacteria in their coelomic fluid than fed urchins. Overall, our data suggests that fasting may ultimately reduce bacteremia and infection in injured or damaged urchins.

PMID: 32053660 [PubMed - indexed for MEDLINE]

Categories: pubmed

PI3K inhibition highlights new molecular interactions involved in the skeletogenesis of Paracentrotus lividus embryos.

Latest Publications - Tue, 04/21/2020 - 23:56
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PI3K inhibition highlights new molecular interactions involved in the skeletogenesis of Paracentrotus lividus embryos.

Biochim Biophys Acta Mol Cell Res. 2020 01;1867(1):118558

Authors: Chiaramonte M, Russo R, Costa C, Bonaventura R, Zito F

Abstract
The sea urchin embryo develops a well-defined biomineralized endoskeleton, synthesized exclusively by the skeletogenic cells, supported by ectodermal cues for the correct skeleton patterning. The biomineralization process is tightly regulated via a hierarchical order of gene expression, including transcription and growth factors, biomineralization proteins. Recently, the role of kinases and intracellular signaling pathways in sea urchin skeletogenesis has been addressed, although the downstream components still remain unknown. In this study, we investigated the role of phosphatidylinositide 3-kinase (PI3K)-mediated signaling pathway in Paracentrotus lividus, to identify its genes/proteins targets. The effects of LY294002 (LY), a PI3K-specific inhibitor, were evaluated at morphological and molecular levels. Treatment with 40 μM LY from the blastula stage completely blocked skeleton deposition, which was reversed by wash out experiments. Besides, LY caused a slight delay in the tripartite gut development. Despite the skeleton absence, a few skeleton-specific proteins/mRNAs were regularly expressed and localized in LY-treated embryos, as shown for MSP130 and SM50 by immunofluorescence and in situ hybridization experiments. QPCR analyses showed that LY differently affected the expression of genes coding for other biomineralization proteins, transcription and growth factors. SM30 and carbonic anhydrase expression was severely downregulated, while almost all the transcription factors analyzed were upregulated. Based on the present results and in silico analyses, we propose an "interactomic" model simulating PI3K connections in P. lividus embryos. Our findings define a novel regulatory step in the embryonic skeletogenesis, and provide valuable molecular data for further studies on the role of PI3K signaling in invertebrate biomineralization.

PMID: 31525406 [PubMed - indexed for MEDLINE]

Categories: pubmed

A wnt2 ortholog in the sea urchin Paracentrotus lividus.

Latest Publications - Tue, 04/21/2020 - 23:56
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A wnt2 ortholog in the sea urchin Paracentrotus lividus.

Genesis. 2019 11;57(11-12):e23331

Authors: Robert N, Hammami F, Lhomond G, Dru P, Lepage T, Schubert M, Croce JC

Abstract
Members of the wnt gene family encode secreted glycoproteins that mediate critical intercellular communications in metazoans. Large-scale genome and transcriptome analyses have shown that this family is composed of 13 distinct subfamilies. These analyses have further established that the number of wnt genes per subfamily varies significantly between metazoan phyla, highlighting that gene duplication and gene loss events have shaped the complements of wnt genes during evolution. In sea urchins, for example, previous work reported the absence of representatives of both the WNT2 and WNT11 subfamilies in two different species, Paracentrotus lividus and Strongylocentrotus purpuratus. Recently, however, we identified a gene encoding a WNT2 ortholog in P. lividus and, based on that finding, we also reanalyzed the genome of S. purpuratus. Yet, we found no evidence of a bona fide wnt2 gene in S. purpuratus. Furthermore, we established that the P. lividus wnt2 gene is selectively expressed in vegetal tissues during embryogenesis, in a pattern that is similar, although not identical, to that of other P. lividus wnt genes. Taken together, this study amends previous work on the P. lividus wnt complement and reveals an unexpected variation in the number of wnt genes between closely related sea urchin species.

PMID: 31479176 [PubMed - indexed for MEDLINE]

Categories: pubmed

BMP controls dorsoventral and neural patterning in indirect-developing hemichordates providing insight into a possible origin of chordates.

Latest Publications - Thu, 04/09/2020 - 23:11
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BMP controls dorsoventral and neural patterning in indirect-developing hemichordates providing insight into a possible origin of chordates.

Proc Natl Acad Sci U S A. 2019 06 25;116(26):12925-12932

Authors: Su YH, Chen YC, Ting HC, Fan TP, Lin CY, Wang KT, Yu JK

Abstract
A defining feature of chordates is the unique presence of a dorsal hollow neural tube that forms by internalization of the ectodermal neural plate specified via inhibition of BMP signaling during gastrulation. While BMP controls dorsoventral (DV) patterning across diverse bilaterians, the BMP-active side is ventral in chordates and dorsal in many other bilaterians. How this phylum-specific DV inversion occurs and whether it is coupled to the emergence of the dorsal neural plate are unknown. Here we explore these questions by investigating an indirect-developing enteropneust from the hemichordate phylum, which together with echinoderms form a sister group of the chordates. We found that in the hemichordate larva, BMP signaling is required for DV patterning and is sufficient to repress neurogenesis. We also found that transient overactivation of BMP signaling during gastrulation concomitantly blocked mouth formation and centralized the nervous system to the ventral ectoderm in both hemichordate and sea urchin larvae. Moreover, this mouthless, neurogenic ventral ectoderm displayed a medial-to-lateral organization similar to that of the chordate neural plate. Thus, indirect-developing deuterostomes use BMP signaling in DV and neural patterning, and an elevated BMP level during gastrulation drives pronounced morphological changes reminiscent of a DV inversion. These findings provide a mechanistic basis to support the hypothesis that an inverse chordate body plan emerged from an indirect-developing ancestor by tinkering with BMP signaling.

PMID: 31189599 [PubMed - indexed for MEDLINE]

Categories: pubmed

Brief exposure to intense turbulence induces a sustained life-history shift in echinoids.

Latest Publications - Thu, 04/09/2020 - 23:11
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Brief exposure to intense turbulence induces a sustained life-history shift in echinoids.

J Exp Biol. 2019 02 21;222(Pt 4):

Authors: Ferner MC, Hodin J, Ng G, Gaylord B

Abstract
In coastal ecosystems, attributes of fluid motion can prompt animal larvae to rise or sink in the water column and to select microhabitats within which they attach and commit to a benthic existence. In echinoid (sea urchin and sand dollar) larvae living along wave-exposed shorelines, intense turbulence characteristic of surf zones can cause individuals to undergo an abrupt life-history shift characterized by precocious entry into competence - the stage at which larvae will settle and complete metamorphosis in response to local cues. However, the mechanistic details of this turbulence-triggered onset of competence remain poorly defined. Here, we evaluate in a series of laboratory experiments the time course of this turbulence effect, both the rapidity with which it initiates and whether it perdures. We found that larvae become competent with turbulence exposures as brief as 30 s, with longer exposures inducing a greater proportion of larvae to become competent. Intriguingly, larvae can remember such exposures for a protracted period (at least 24 h), a pattern reminiscent of long-term potentiation. Turbulence also induces short-term behavioral responses that last less than 30 min, including cessation of swimming, that facilitate sinking and thus contact of echinoid larvae with the substratum. Together, these results yield a novel perspective on how larvae find their way to suitable adult habitat at the critical settlement transition, and also open new experimental opportunities to elucidate the mechanisms by which planktonic animals respond to fluid motion.

PMID: 30573667 [PubMed - indexed for MEDLINE]

Categories: pubmed