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Craig R. Tomlinson - One of the best experts on this subject based on the ideXlab platform.
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USF in the Lytechinus sea urchin embryo may act as a transcriptional repressor in non-aboral ectoderm cells for the cell lineage-specific expression of the LpS1 genes
Journal of molecular biology, 1996Co-Authors: Christopher A. Seid, Jenny M. George, Amy K. Sater, Mark T. Kozlowski, Haemin Lee, Venkatesh Govindarajan, Ravi K. Ramachandran, Craig R. TomlinsonAbstract:Abstract Expression of the aboral ectoderm-specific LpS1 gene in Lytechinus was used to study lineage-specific transcriptional regulation during sea urchin development. Band shift assays using anti-USF antibody showed that a USF-like protein bound the USF core sequence 5′-CACGTG-3′ in the promoter of the LpS1 gene. DNA constructs consisting of a wild-type LpS1 promoter and the same LpS1 promoter with a mutated USF binding site fused to the bacterial chloramphenicol acetyltransferase reporter gene were tested. The mutation in the USF binding site caused an increase in chloramphenicol acetyltransferse activity. We selected a clone that encodes USF, LvUSF, from a gastrula-stage cDNA library representing Lytechinus variegatus . Transactivation experiments, in which LvUSF RNA or a DNA construct consisting of the LvUSF cDNA clone fused to the Lytechinus pictus metallothionein promoter coinjected with the wild-type or mutated LpS1 promoter-chloramphenicol acetyltransferase gene construct, showed that chloramphenicol acetyltransferase activity from the wild-type construct was repressed, while the construct mutated at the USF binding site was active. The same wild-type and mutated LpS1 promoter DNA fragments ligated to the green fluorescent protein reporter gene were used to examine spatial expression. The reporter gene constructs containing the mutated USF binding site were expressed inappropriately in all cell types including the gut and oral ectoderm in gastrula and larva stage embryos, while the wild-type constructs were expressed primarily in the aboral ectoderm. USF was expressed in all cells of the early embryo and in all tissues except the aboral ectoderm in later embryos. The data are consistent with a model depicting Lytechinus USF, as a temporal and spatial regulator by repressing LpS1 gene transcription in non-aboral ectoderm cells.
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A tissue-specific repressor in the sea urchin embryo of Lytechinus pictus binds the distal G-string element in the LpS1-beta promoter.
DNA and cell biology, 1996Co-Authors: Christopher A. Seid, Amy K. Sater, Richard L. Falzone, Craig R. TomlinsonAbstract:ABSTRACT LpS1 RNA transcripts and proteins are expressed exclusively in the aboral ectoderm of the embryo in the sea urchin Lytechinus pictus. We have characterized the LpS1-β promoter to identify ...
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Two distinct forms of USF in the Lytechinus sea urchin embryo do not play a role in LpS1 gene inactivation upon disruption of the extracellular matrix
Molecular reproduction and development, 1996Co-Authors: Jenny M. George, Christopher A. Seid, Haemin Lee, Craig R. TomlinsonAbstract:Recent studies in our laboratory indicated that the upstream stimulatory factor (USF) in the sea urchin embryo of Lytechinus acts as a transcriptional repressor for the aboral ectoderm-specific expression of the LpS1 genes. Disruption of the extracellular matrix (ECM) arrests development prior to gastrulation and inactivates the LpS1 genes. We wanted to determine whether the inactivation of the LpS1 genes by ECM disruption may be due to an increase in USF expression. In the course of the investigation, a second L, variegatus USF cDNA clone (LvUSF2) was isolated and sequenced. The deduced amino acid sequence of LvUSF2 is nearly identical to LvUSF1 except at the amino end, where they are sharply divergent. Like LvUSF1, LvUSF2 has a USF-specific, a basic/hefixloop-helix, and a leucine zipper domain. Genomic DNA blots indicated that the two cDNA clones are derived from one gene, which suggested that the Lytechinus USF1 and USF2 mRNAs, of approximately 6.0 and 4.0 kb, respectively, are the result of differential RNA splicing. ECM disruption in Lytechinus embryos caused a relative drop in USF RNA accumulation levels to approximately 60% of control embryos, while LpS1 RNA accumulation levels dropped to less than 5%. USF protein levels and DNA binding activities in ECM-disrupted embryos also dropped to approximately 60% to that of control embryos. A mutation at the USF binding site in an LpS1 promoter-chloramphenicol acetyl transferase (CAT) fusion DNA construct did not cause a relative increase in CAT activity in ECM disrupted embryos. These results suggest that the induced drop in LpS1 gene expression by ECM disruption is not due to an increase in the repressive activity of USF.
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Role for platelet-derived growth factor-like and epidermal growth factor-like signaling pathways in gastrulation and spiculogenesis in the Lytechinus sea urchin embryo
Developmental dynamics : an official publication of the American Association of Anatomists, 1995Co-Authors: Ravi K. Ramachandran, Christopher A. Seid, Venkatesh Govindarajan, Sonali Patil, Craig R. TomlinsonAbstract:The mechanisms underlying sea urchin gastrulation and spiculogenesis have been sought for decades. We have identified two growth factor signaling pathways that are involved in these developmental events. Antibodies against mammalian platelet-derived growth factor (PDGF) receptor-beta inhibited gastrulation and spiculogenesis, and antibodies against human epidermal growth factor (EGF) receptor disrupted gastrulation and spicule placement in Lytechinus pictus and L. variegatus embryos. Our studies suggested that the antibodies affect development by inhibiting rather than activating the signaling pathways. Polyclonal and monoclonal antibodies against the mammalian receptors recognized specifically Lytechinus proteins of the expected size of 170-180 x 10(3) M(r). Growth factor binding assays indicated that there are approximately 1.25 x 10(4) platelet-derived growth factor-like receptors per cell at the mesenchyme blastula stage of L. pictus, and human platelet-derived growth factor bound with an apparent affinity of KD = 4.4 nM to dissociated cells at the mesenchyme blastula stage. Immunolabelling experiments showed that at the gastrula stage, the Lytechinus platelet-derived growth factor-like receptors are located on the primary mesenchyme cells, the gut, and most prominently on the secondary mesenchyme cells and the stomodeum. The epidermal growth factor-like receptors stained less intensely on the gut and primary and secondary mesenchyme cells. Both receptors are expressed on the ciliary band and the gut of the pluteus larva but only the PDGF-like receptor is expressed on the primary mesenchyme cells. Pulse studies showed that the embryos are sensitive to the platelet-derived growth factor receptor-beta and epidermal growth factor receptor antibodies from the blastula to sometime between the mesenchyme blastula and midgastrula stages. We show that antibodies enter the blastocoel as late as the gastrula stage. Our results suggest that platelet-derived growth factor-like and epidermal growth factor-like signaling pathways are involved in the early differentiation and morphogenesis of the sea urchin gut and spicules.
Eric H. Davidson - One of the best experts on this subject based on the ideXlab platform.
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Flexibility of transcription factor target site position in conserved cis-regulatory modules.
Developmental biology, 2009Co-Authors: R. Andrew Cameron, Eric H. DavidsonAbstract:Eight Strongylocentrotus purpuratus cis-regulatory modules, in each of which up to three different transcription factor target sites had been previously authenticated in gene transfer and mutagenesis studies, were compared to the orthologous modules in the genome of Lytechinus variegatus. These species diverged about 50 million years ago. The orthologous modules were identified in sequenced Lytechinus BACs, as conserved sequence patches in similar regions of the respective genes. The similar functionality of several of these control modules in the two species was confirmed by cross-species gene transfer experiments. In each case the repertoire of transcription factor target sites was the same in the orthologous modules, but the positions of the individual sites with respect to one another was evolutionarily flexible, even though the intervening sequence was often strongly conserved. The most invariably conserved features, as seen also in other systems, were pairs of target sites that are immediately adjacent to one another. Their conservation is probably due to the necessity for interaction of proximally bound transcription factors, while a facilitated form of sequence conversion might be the mechanism of site position change.
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Comparison of the bindin proteins of Strongylocentrotus franciscanus, S. purpuratus, and Lytechinus variegatus: sequences involved in the species specificity of fertilization.
Molecular Biology and Evolution, 1991Co-Authors: Joseph E. Minor, David R. Fromson, Roy J. Britten, Eric H. DavidsonAbstract:Bindin is the sea urchin sperm acrosomal protein that is responsible for the species-specific adhesion of the sperm to the egg. Two new bindin cDNA sequences that contain the entire open reading frame for the binding precursor are reported: one for Strongylocentrotus franciscanus and one for Lytechinus variegatus. Both contain inverted repetitive sequences in their 3' untranslated regions, and the S. franciscanus cDNA contains an inverted repetitive sequence match between the 5' untranslated region and the coding region. The middle third of the mature bindin sequence is highly conserved in all three species, and the flanking sequences share short repeated sequences that vary in number between the species. Cross-fertilization data are reported for the species S. purpuratus, S. franciscanus, L. variegatus, and L. pictus. A barrier to cross-fertilization exists between the sympatric Strongylocentrotus species, but there is no barrier between the allopatric Lytechinus species.
John M. Lawrence - One of the best experts on this subject based on the ideXlab platform.
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chapter 31 Lytechinus
Developments in Aquaculture and Fisheries Science, 2013Co-Authors: Stephen A. Watts, James B Mcclintock, John M. LawrenceAbstract:Tripneustes appears to be a generalist in habitat and food in tropical and subtropical, shallow-water habitats subject to disturbance. It can have major effects on seagrass and algal beds and cause barren grounds. Tripneustes has rapid growth, early maturation, high fecundity, sporadic and potentially high recruitment, and short longevity. All are characteristics of a ruderal species.
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Chapter 31 – Lytechinus
Developments in Aquaculture and Fisheries Science, 2013Co-Authors: Stephen A. Watts, James B Mcclintock, John M. LawrenceAbstract:Tripneustes appears to be a generalist in habitat and food in tropical and subtropical, shallow-water habitats subject to disturbance. It can have major effects on seagrass and algal beds and cause barren grounds. Tripneustes has rapid growth, early maturation, high fecundity, sporadic and potentially high recruitment, and short longevity. All are characteristics of a ruderal species.
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Chapter 23 Ecology of Lytechinus
Developments in Aquaculture and Fisheries Science, 2007Co-Authors: Stephen A. Watts, James B Mcclintock, John M. LawrenceAbstract:Publisher Summary Lytechinus species are dominant in many habitats. Lytechinus variegatus ( L. variegatus ) occurs in a great variety of habitats in shallow water, but the ecological role is primarily known for L. variegatus . In shallow water, the habitat densities of L. variegatus can vary, both seasonally and annually, and densities are generally less than 15 individuals per square meter. In some areas, populations may display a highly patchy spatial distribution. The absence of L. variegatus in an appropriate habitat may be the result of episodic biotic or abiotic factors, particularly in nearshore populations, such as in a bay or lagoon. As a ruderal genus, L. variegatus exhibits characteristics of a ruderal species: rapid growth, early reproductive maturity, and short longevity. Temperature is the most important factor influencing the distribution and abundance of L. variegatus , both latitudinally and locally. Omnivory is the most common strategy used by L. variegatus . The reproductive cycle of L. variegatus varies widely, depending on the location and, most likely, environmental conditions. The primary predators of L. variegatus are fish and several macroinvertebrates.
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interactive effects of temperature and nutritional condition on the energy budgets of the sea urchins arbacia punctulata and Lytechinus variegatus echinodermata echinoidea
Journal of the Marine Biological Association of the United Kingdom, 2006Co-Authors: Sophie K Hill, John M. LawrenceAbstract:Arbacia punctulata and Lytechinus variegatus are widely distributed echinoid species in shallow water in the western Atlantic Ocean, Caribbean Sea and Gulf of Mexico that seem to have diierent life history strategies. We evaluated the eiect of two types of stress (high temperature and starvation) on gonad production and scope for growth. We hypothesized that A. punctulata has a stress tolerant life strategy and would be more tolerant to stress and L. variegatus has a competitive ^ ruderal strategy and would be less tolerant to stress. Gonad production by A. punctulata was not as greatly aiected by temperature as L. variegatus, suggesting the hypothesis was correct. Arbacia punctulata had a signi¢cantly higher excretion rate indicating greater energy allocation to maintenance than production. Lytechinus variegatus had a signi¢cantly greater consumption rate but did not absorb signi¢cantly more energy. Arbacia punctulata compensated for its lower food consumption by a higher absorption e⁄ciency. Measured energy expenditure and calculated scope for growth did not diier. However, the percentage change in energy absorbed and energy expenditure was greater for L. variegatus than for A. punctulata with a change in temperature. Feeding had a greater eiect on production than temperature suggesting that the biotic stress of low food availability is more important than an abiotic stress such as temperature on energy budgets.
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habitats and characteristics of the sea urchins Lytechinus variegatus and arbacia punctulata echinodermata on the florida gulf coast shelf
Marine Ecology, 2003Co-Authors: Sophie K Hill, John M. LawrenceAbstract:Abstract Lytechinus variegatus and Arbacia punctulata have been studied primarily in inshore, shallow-water areas. However, they are abundant in deeper waters on the Florida gulf-coast shelf and seem important components of the benthic communities there. Lytechinus variegatus occurs alone on sand bottoms and A. punctulata occurs alone on rubble bottoms in these deeper waters. The species also co-occur there on heterogeneous bottoms, each in a distinct microhabitat with A. punctulata on rubble and L. variegatus on surrounding sand. Characteristics of the sea urchins in these different deeper-water habitat types and at one nearshore site with a heterogeneous rubble-sand bottom were compared. Over the 2-year study, offshore individuals of both species had low gut and gonad indices and the maximum size of individuals did not change. This suggests food limitation and low production. Offshore, A. punctulata had a higher Aristotle's lantern index and lower gut and gonad indices in populations where it co-occurred with L. variegatus compared to populations where it occurred alone. The Aristotle's lantern index of L. variegatus did not differ among the offshore sites. Neither species seemed food limited at the nearshore site. Although productivity is lower at the offshore sites, both species extend their distribution and reproduction potential by existing there.
James B Mcclintock - One of the best experts on this subject based on the ideXlab platform.
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Chapter 31 – Lytechinus
Developments in Aquaculture and Fisheries Science, 2013Co-Authors: Stephen A. Watts, James B Mcclintock, John M. LawrenceAbstract:Tripneustes appears to be a generalist in habitat and food in tropical and subtropical, shallow-water habitats subject to disturbance. It can have major effects on seagrass and algal beds and cause barren grounds. Tripneustes has rapid growth, early maturation, high fecundity, sporadic and potentially high recruitment, and short longevity. All are characteristics of a ruderal species.
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chapter 31 Lytechinus
Developments in Aquaculture and Fisheries Science, 2013Co-Authors: Stephen A. Watts, James B Mcclintock, John M. LawrenceAbstract:Tripneustes appears to be a generalist in habitat and food in tropical and subtropical, shallow-water habitats subject to disturbance. It can have major effects on seagrass and algal beds and cause barren grounds. Tripneustes has rapid growth, early maturation, high fecundity, sporadic and potentially high recruitment, and short longevity. All are characteristics of a ruderal species.
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Acetyl cholinesterase activity and muscle contraction in the sea urchin Lytechinus variegatus (Lamarck) following chronic phosphate exposure.
Environmental Toxicology, 2010Co-Authors: S. Anne Boettger, James B McclintockAbstract:The common shallow-water sea urchin Lytechinus variegatus is capable of surviving inorganic phosphate exposures as high as 3.2 mg L−1 and organic phosphate exposures of 1000 mg L−1. Nonetheless, chronic exposure to low, medium, and high-sublethal concentrations of organic phosphate inhibits the muscle enzyme acetyl cholinesterase (AChE), responsible for the break down of the neurotransmitter acetylcholine, as well as inhibiting contractions in the muscles associated with the Aristotle's lantern. AChE activity, measured in both a static enzyme assay and by vesicular staining, displayed concentration-dependent declines of activity in individuals maintained in organic phosphate for 4 weeks. The activity of AChE was not adversely affected by exposure to inorganic phosphate or seawater controls over the same time period. Maximum force of muscle contraction and rates of muscle contraction and relaxation also decreased with chronic exposure to increasing concentrations of organic phosphate. Chronic exposure to inorganic phosphates elicited no response except at the highest concentration, where the maximum force of muscular contraction increased compared to controls. These findings indicate that shallow-water populations of Lytechinus variegatus subjected to organic phosphate pollutants may display impaired muscular activity that is potentially related to the inhibition of the muscle relaxant enzyme AChE, and subsequently muscular overstimulation, and fatigue. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.
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Acetyl cholinesterase activity and muscle contraction in the sea urchin Lytechinus variegatus (Lamarck) following chronic phosphate exposure.
Environmental toxicology, 2010Co-Authors: S. Anne Boettger, James B McclintockAbstract:The common shallow-water sea urchin Lytechinus variegatus is capable of surviving inorganic phosphate exposures as high as 3.2 mg L(-1) and organic phosphate exposures of 1000 mg L(-1) . Nonetheless, chronic exposure to low, medium, and high-sublethal concentrations of organic phosphate inhibits the muscle enzyme acetyl cholinesterase (AChE), responsible for the break down of the neurotransmitter acetylcholine, as well as inhibiting contractions in the muscles associated with the Aristotle's lantern. AChE activity, measured in both a static enzyme assay and by vesicular staining, displayed concentration-dependent declines of activity in individuals maintained in organic phosphate for 4 weeks. The activity of AChE was not adversely affected by exposure to inorganic phosphate or seawater controls over the same time period. Maximum force of muscle contraction and rates of muscle contraction and relaxation also decreased with chronic exposure to increasing concentrations of organic phosphate. Chronic exposure to inorganic phosphates elicited no response except at the highest concentration, where the maximum force of muscular contraction increased compared to controls. These findings indicate that shallow-water populations of Lytechinus variegatus subjected to organic phosphate pollutants may display impaired muscular activity that is potentially related to the inhibition of the muscle relaxant enzyme AChE, and subsequently muscular overstimulation, and fatigue.
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Chapter 23 Ecology of Lytechinus
Developments in Aquaculture and Fisheries Science, 2007Co-Authors: Stephen A. Watts, James B Mcclintock, John M. LawrenceAbstract:Publisher Summary Lytechinus species are dominant in many habitats. Lytechinus variegatus ( L. variegatus ) occurs in a great variety of habitats in shallow water, but the ecological role is primarily known for L. variegatus . In shallow water, the habitat densities of L. variegatus can vary, both seasonally and annually, and densities are generally less than 15 individuals per square meter. In some areas, populations may display a highly patchy spatial distribution. The absence of L. variegatus in an appropriate habitat may be the result of episodic biotic or abiotic factors, particularly in nearshore populations, such as in a bay or lagoon. As a ruderal genus, L. variegatus exhibits characteristics of a ruderal species: rapid growth, early reproductive maturity, and short longevity. Temperature is the most important factor influencing the distribution and abundance of L. variegatus , both latitudinally and locally. Omnivory is the most common strategy used by L. variegatus . The reproductive cycle of L. variegatus varies widely, depending on the location and, most likely, environmental conditions. The primary predators of L. variegatus are fish and several macroinvertebrates.
Christopher A. Seid - One of the best experts on this subject based on the ideXlab platform.
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USF in the Lytechinus sea urchin embryo may act as a transcriptional repressor in non-aboral ectoderm cells for the cell lineage-specific expression of the LpS1 genes
Journal of molecular biology, 1996Co-Authors: Christopher A. Seid, Jenny M. George, Amy K. Sater, Mark T. Kozlowski, Haemin Lee, Venkatesh Govindarajan, Ravi K. Ramachandran, Craig R. TomlinsonAbstract:Abstract Expression of the aboral ectoderm-specific LpS1 gene in Lytechinus was used to study lineage-specific transcriptional regulation during sea urchin development. Band shift assays using anti-USF antibody showed that a USF-like protein bound the USF core sequence 5′-CACGTG-3′ in the promoter of the LpS1 gene. DNA constructs consisting of a wild-type LpS1 promoter and the same LpS1 promoter with a mutated USF binding site fused to the bacterial chloramphenicol acetyltransferase reporter gene were tested. The mutation in the USF binding site caused an increase in chloramphenicol acetyltransferse activity. We selected a clone that encodes USF, LvUSF, from a gastrula-stage cDNA library representing Lytechinus variegatus . Transactivation experiments, in which LvUSF RNA or a DNA construct consisting of the LvUSF cDNA clone fused to the Lytechinus pictus metallothionein promoter coinjected with the wild-type or mutated LpS1 promoter-chloramphenicol acetyltransferase gene construct, showed that chloramphenicol acetyltransferase activity from the wild-type construct was repressed, while the construct mutated at the USF binding site was active. The same wild-type and mutated LpS1 promoter DNA fragments ligated to the green fluorescent protein reporter gene were used to examine spatial expression. The reporter gene constructs containing the mutated USF binding site were expressed inappropriately in all cell types including the gut and oral ectoderm in gastrula and larva stage embryos, while the wild-type constructs were expressed primarily in the aboral ectoderm. USF was expressed in all cells of the early embryo and in all tissues except the aboral ectoderm in later embryos. The data are consistent with a model depicting Lytechinus USF, as a temporal and spatial regulator by repressing LpS1 gene transcription in non-aboral ectoderm cells.
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A tissue-specific repressor in the sea urchin embryo of Lytechinus pictus binds the distal G-string element in the LpS1-beta promoter.
DNA and cell biology, 1996Co-Authors: Christopher A. Seid, Amy K. Sater, Richard L. Falzone, Craig R. TomlinsonAbstract:ABSTRACT LpS1 RNA transcripts and proteins are expressed exclusively in the aboral ectoderm of the embryo in the sea urchin Lytechinus pictus. We have characterized the LpS1-β promoter to identify ...
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Two distinct forms of USF in the Lytechinus sea urchin embryo do not play a role in LpS1 gene inactivation upon disruption of the extracellular matrix
Molecular reproduction and development, 1996Co-Authors: Jenny M. George, Christopher A. Seid, Haemin Lee, Craig R. TomlinsonAbstract:Recent studies in our laboratory indicated that the upstream stimulatory factor (USF) in the sea urchin embryo of Lytechinus acts as a transcriptional repressor for the aboral ectoderm-specific expression of the LpS1 genes. Disruption of the extracellular matrix (ECM) arrests development prior to gastrulation and inactivates the LpS1 genes. We wanted to determine whether the inactivation of the LpS1 genes by ECM disruption may be due to an increase in USF expression. In the course of the investigation, a second L, variegatus USF cDNA clone (LvUSF2) was isolated and sequenced. The deduced amino acid sequence of LvUSF2 is nearly identical to LvUSF1 except at the amino end, where they are sharply divergent. Like LvUSF1, LvUSF2 has a USF-specific, a basic/hefixloop-helix, and a leucine zipper domain. Genomic DNA blots indicated that the two cDNA clones are derived from one gene, which suggested that the Lytechinus USF1 and USF2 mRNAs, of approximately 6.0 and 4.0 kb, respectively, are the result of differential RNA splicing. ECM disruption in Lytechinus embryos caused a relative drop in USF RNA accumulation levels to approximately 60% of control embryos, while LpS1 RNA accumulation levels dropped to less than 5%. USF protein levels and DNA binding activities in ECM-disrupted embryos also dropped to approximately 60% to that of control embryos. A mutation at the USF binding site in an LpS1 promoter-chloramphenicol acetyl transferase (CAT) fusion DNA construct did not cause a relative increase in CAT activity in ECM disrupted embryos. These results suggest that the induced drop in LpS1 gene expression by ECM disruption is not due to an increase in the repressive activity of USF.
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Role for platelet-derived growth factor-like and epidermal growth factor-like signaling pathways in gastrulation and spiculogenesis in the Lytechinus sea urchin embryo
Developmental dynamics : an official publication of the American Association of Anatomists, 1995Co-Authors: Ravi K. Ramachandran, Christopher A. Seid, Venkatesh Govindarajan, Sonali Patil, Craig R. TomlinsonAbstract:The mechanisms underlying sea urchin gastrulation and spiculogenesis have been sought for decades. We have identified two growth factor signaling pathways that are involved in these developmental events. Antibodies against mammalian platelet-derived growth factor (PDGF) receptor-beta inhibited gastrulation and spiculogenesis, and antibodies against human epidermal growth factor (EGF) receptor disrupted gastrulation and spicule placement in Lytechinus pictus and L. variegatus embryos. Our studies suggested that the antibodies affect development by inhibiting rather than activating the signaling pathways. Polyclonal and monoclonal antibodies against the mammalian receptors recognized specifically Lytechinus proteins of the expected size of 170-180 x 10(3) M(r). Growth factor binding assays indicated that there are approximately 1.25 x 10(4) platelet-derived growth factor-like receptors per cell at the mesenchyme blastula stage of L. pictus, and human platelet-derived growth factor bound with an apparent affinity of KD = 4.4 nM to dissociated cells at the mesenchyme blastula stage. Immunolabelling experiments showed that at the gastrula stage, the Lytechinus platelet-derived growth factor-like receptors are located on the primary mesenchyme cells, the gut, and most prominently on the secondary mesenchyme cells and the stomodeum. The epidermal growth factor-like receptors stained less intensely on the gut and primary and secondary mesenchyme cells. Both receptors are expressed on the ciliary band and the gut of the pluteus larva but only the PDGF-like receptor is expressed on the primary mesenchyme cells. Pulse studies showed that the embryos are sensitive to the platelet-derived growth factor receptor-beta and epidermal growth factor receptor antibodies from the blastula to sometime between the mesenchyme blastula and midgastrula stages. We show that antibodies enter the blastocoel as late as the gastrula stage. Our results suggest that platelet-derived growth factor-like and epidermal growth factor-like signaling pathways are involved in the early differentiation and morphogenesis of the sea urchin gut and spicules.
