A Rho-signaling pathway mediates cortical granule translocation in the sea urchin oocyte

Eggs of many species including those of echinoderms, amphibians and mammals exhibit an extensive extracellular matrix (ECM) that is important both in the reception of sperm and in providing a block to polyspermy after fertilization.In sea urchin eggs there are two distinctive coats, the vitelline layer which contains glycoprotein sperm receptors and the jelly layer that contains fucose sulfate glycoconjugates which trigger the acrosomal reaction and small peptides which act as chemoattractants for sperm. The vitelline layer (VL), as visualized by quick-freezing, deep-etching, and rotary-shadowing (QFDE-RS), is a fishnet-like structure, anchored to the plasma membrane by short posts. Orbiting above the VL are horizontal filaments which are thought to anchor the thicker jelly layer to the egg. Upon fertilization, the VL elevates and is transformed by cortical granule secretions into the fertilization envelope (FE). The rounded casts of microvilli in the VL are transformed into angular peaks and the envelope becomes coated inside and out with sheets of paracrystalline protein having a quasi-two dimensional crystalline structure.

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Sea urchin larvae utilize light for regulating the pyloric opening

BMC Biology ◽

10.1186/s12915-021-00999-1 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Junko Yaguchi ◽

Shunsuke Yaguchi

Keyword(s):

Signaling Pathway ◽

Digestive Tract ◽

Sea Urchin ◽

Visual Information ◽

Biological Activities ◽

Regulatory System ◽

Sister Group ◽

Animal Evolution ◽

Deuterostome Evolution ◽

Visual Systems

Abstract Background Light is essential for various biological activities. In particular, visual information through eyes or eyespots is very important for most of animals, and thus, the functions and developmental mechanisms of visual systems have been well studied to date. In addition, light-dependent non-visual systems expressing photoreceptor Opsins have been used to study the effects of light on diverse animal behaviors. However, it remains unclear how light-dependent systems were acquired and diversified during deuterostome evolution due to an almost complete lack of knowledge on the light-response signaling pathway in Ambulacraria, one of the major groups of deuterostomes and a sister group of chordates. Results Here, we show that sea urchin larvae utilize light for digestive tract activity. We found that photoirradiation of larvae induces pyloric opening even without addition of food stimuli. Micro-surgical and knockdown experiments revealed that this stimulating light is received and mediated by Go(/RGR)-Opsin (Opsin3.2 in sea urchin genomes) cells around the anterior neuroectoderm. Furthermore, we found that the anterior neuroectodermal serotoninergic neurons near Go-Opsin-expressing cells are essential for mediating light stimuli-induced nitric oxide (NO) release at the pylorus. Our results demonstrate that the light>Go-Opsin>serotonin>NO pathway functions in pyloric opening during larval stages. Conclusions The results shown here will lead us to understand how light-dependent systems of pyloric opening functioning via neurotransmitters were acquired and established during animal evolution. Based on the similarity of nervous system patterns and the gut proportions among Ambulacraria, we suggest the light>pyloric opening pathway may be conserved in the clade, although the light signaling pathway has so far not been reported in other members of the group. In light of brain-gut interactions previously found in vertebrates, we speculate that one primitive function of anterior neuroectodermal neurons (brain neurons) may have been to regulate the function of the digestive tract in the common ancestor of deuterostomes. Given that food consumption and nutrient absorption are essential for animals, the acquirement and development of brain-based sophisticated gut regulatory system might have been important for deuterostome evolution.

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An ultrastructural study of cross-fertilization (Arbacia female x Mytilus male).

The Journal of Cell Biology ◽

10.1083/jcb.73.1.14 ◽

1977 ◽

Vol 73 (1) ◽

pp. 14-26 ◽

Cited By ~ 22

Author(s):

F J Longo

Keyword(s):

Sea Urchin ◽

Ultrastructural Study ◽

Cortical Granule ◽

Male Pronucleus ◽

Female Pronucleus ◽

Sperm Nuclei ◽

Cross Fertilization ◽

Sperm Aster

Insemination of sea urchin (Arbacia) ova with mussel (Mytilus) sperm has been accomplished by treating eggs with trypsin and suspending the gametes in seawater made alkaline with NaOH. Not all inseminated eggs undergo a cortical granule reaction. Some eggs either elevate what remains of their vitelline layer or demonstrate no cortical modification whatsoever. After its incorporation into the egg, the nucleus of Mytilus sperm undergoes changes which eventually give rise to the formation of a male pronucleus. Concomitant with these transformations, a sperm aster may develop in association with the centrioles brought into the egg with the spermatozoon. Both the male pronucleus and the sperm aster may then migrate centrad to the female pronucleus. Evidence is presented which suggests that fusion of the male pronuclei from Mytilus sperm with female pronuclei from Arbacia eggs may occur, although this was not directly observed. These results demonstrate that Mytilus sperm nuclei are able to react to conditions within Arbacia eggs and differentiate into male pronuclei.

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OOCYTE DIFFERENTIATION IN THE SEA URCHIN, ARBACIA PUNCTULATA, WITH PARTICULAR REFERENCE TO THE ORIGIN OF CORTICAL GRANULES AND THEIR PARTICIPATION IN THE CORTICAL REACTION

The Journal of Cell Biology ◽

10.1083/jcb.37.2.514 ◽

1968 ◽

Vol 37 (2) ◽

pp. 514-539 ◽

Cited By ~ 198

Author(s):

Everett Anderson

Keyword(s):

Sea Urchin ◽

Golgi Complex ◽

Morphological Evidence ◽

Cortical Granule ◽

Perivitelline Space ◽

Unit Membrane ◽

Cortical Granules ◽

Arbacia Punctulata ◽

Cortical Reaction ◽

Oocyte Differentiation

This paper presents morphological evidence on the origin of cortical granules in the oocytes of Arbacia punctulata and other echinoderms. During oocyte differentiation, those Golgi complexes associated with the production of cortical granules are composed of numerous saccules with companion vesicles. Each element of the Golgi complex contains a rather dense homogeneous substance. The vesicular component of the Golgi complex is thought to be derived from the saccular member by a pinching-off process. The pinched-off vesicles are viewed as containers of the precursor(s) of the cortical granules. In time, they coalesce and form a mature cortical granule whose content is bounded by a unit membrane. Thus, it is asserted that the Golgi complex is involved in both the synthesis and concentration of precursors utilized in the construction of the cortical granule. Immediately after the egg is activated by the sperm the primary envelope becomes detached from the oolemma, thereby forming what we have called the activation calyx (see Discussion). Subsequent to the elaboration of the activation calyx, the contents of cortical granules are released (cortical reaction) into the perivitelline space. The discharge of the constituents of a cortical granule is accomplished by the union of its encompassing unit membrane, in several places, with the oolemma.

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Poisson-distributed active fusion complexes underlie the control of the rate and extent of exocytosis by calcium.

The Journal of Cell Biology ◽

10.1083/jcb.134.2.329 ◽

1996 ◽

Vol 134 (2) ◽

pp. 329-338 ◽

Cited By ~ 35

Author(s):

S S Vogel ◽

P S Blank ◽

J Zimmerberg

Keyword(s):

Poisson Process ◽

Sea Urchin ◽

Physiological Responses ◽

Cortical Granule ◽

Cortical Granules ◽

Granule Exocytosis ◽

Calcium Dependence ◽

Sea Urchin Egg ◽

High Calcium ◽

Cortical Granule Exocytosis

We have investigated the consequences of having multiple fusion complexes on exocytotic granules, and have identified a new principle for interpreting the calcium dependence of calcium-triggered exocytosis. Strikingly different physiological responses to calcium are expected when active fusion complexes are distributed between granules in a deterministic or probabilistic manner. We have modeled these differences, and compared them with the calcium dependence of sea urchin egg cortical granule exocytosis. From the calcium dependence of cortical granule exocytosis, and from the exposure time and concentration dependence of N-ethylmaleimide inhibition, we determined that cortical granules do have spare active fusion complexes that are randomly distributed as a Poisson process among the population of granules. At high calcium concentrations, docking sites have on average nine active fusion complexes.

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Phosphoprotein inhibition of calcium-stimulated exocytosis in sea urchin eggs.

The Journal of Cell Biology ◽

10.1083/jcb.113.4.769 ◽

1991 ◽

Vol 113 (4) ◽

pp. 769-778 ◽

Cited By ~ 21

Author(s):

T Whalley ◽

I Crossley ◽

M Whitaker

Keyword(s):

Sea Urchin ◽

Okadaic Acid ◽

Cortical Granule ◽

Granule Exocytosis ◽

Sea Urchin Eggs ◽

Transduction Mechanisms ◽

Egg Signal ◽

Cortical Granule Exocytosis ◽

Gamma S

We have investigated the role of protein phosphorylation in the control of exocytosis in sea urchin eggs by treating eggs with a thio-analogue of ATP. ATP gamma S (adenosine 5'-O-3-thiotriphosphate) is a compound which can be used as a phosphoryl donor by protein kinases, leading to irreversible protein thiophosphorylation (Gratecos, D., and E.H. Fischer. 1974. Biochem. Biophys. Res. Commun. 58:960-967). Microinjection of ATP gamma S inhibits cortical granule exocytosis, but has no effect on the sperm-egg signal transduction mechanisms which normally cause exocytosis by generating an increase in [Ca2+]i. ATP gamma S requires cytosolic factors for its inhibition of cortical granule exocytosis: it does not affect exocytosis when applied directly to the isolated exocytotic apparatus. Our data suggest that ATP gamma S irreversibly inhibits exocytosis via thiophosphorylation of proteins associated with the egg cortex. We have identified two thiophosphorylated proteins (33 and 27 kD) that are associated with the isolated exocytotic apparatus. They may mediate the inhibition of exocytosis by ATP gamma S. In addition, we show that okadaic acid, an inhibitor of phosphoprotein phosphatases, prevents cortical granule exocytosis at fertilization without affecting calcium mobilization. Like ATP gamma S, okadaic acid has no effect on exocytosis in vitro. Our results suggest that an inhibitory phosphoprotein can obstruct calcium-stimulated exocytosis in sea urchin eggs; on the other hand, they do not readily support the idea that a protein phosphatase is an essential component of the mechanism controlling exocytosis.

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Cortical Granule Exocytosis and Fertilization Coat Elevation is Reduced in Aging Sea Urchin Eggs

Microscopy and Microanalysis ◽

10.1017/s1431927600037326 ◽

2000 ◽

Vol 6 (S2) ◽

pp. 966-967

Author(s):

Amitabha Chakrabarti ◽

Heide Schatten

Keyword(s):

Plasma Membrane ◽

Sea Urchin ◽

Sea Water ◽

Secretory Granules ◽

Cortical Granule ◽

Cortical Granules ◽

Lytechinus Pictus ◽

Sea Urchin Eggs ◽

Cortical Granule Exocytosis ◽

Granule Secretion

Cortical granules are specialized Golgi-derived membrane-bound secretory granules that are located beneath the plasma membrane in unfertilized sea urchin eggs. Upon fertilization cortical granules discharge in a reaction induced by calcium and release their contents between the plasma membrane and a thin vitelline layer that lines the plasma membrane. Microvilli at the plasma membrane elongate incorporting cortical granule membranes during elongation. The vitelline layer elevates and becomes the egg's fertilization coat that hardens and serves as physical block to polyspermy. While we do not understand the precise mechanisms that participate in cortical granule discharge it is believed that actin plays a role in this process. Because actin and calcium metabolism is affected in aging cells we investigated if cortical granule secretion is affected in aging sea urchin eggs.Lytechinus pictus eggs were obtained by intracoelomic injection of 0.5M KCI to release the eggs into sea water at 23°C.

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Revisiting the Role of H+ in Chemotactic Signaling of Sperm

The Journal of General Physiology ◽

10.1085/jgp.200409030 ◽

2004 ◽

Vol 124 (2) ◽

pp. 115-124 ◽

Cited By ~ 21

Author(s):

Johannes Solzin ◽

Annika Helbig ◽

Qui Van ◽

Joel E. Brown ◽

Eilo Hildebrand ◽

...

Keyword(s):

Signaling Pathway ◽

Sea Urchin ◽

Kinetic Measurements ◽

Arbacia Punctulata ◽

Cellular Events ◽

Intracellular Release ◽

Proposal A ◽

Voltage Dependent ◽

Chemotactic Behavior

Chemotaxis of sperm is an important step toward fertilization. During chemotaxis, sperm change their swimming behavior in a gradient of the chemoattractant that is released by the eggs, and finally sperm accumulate near the eggs. A well established model to study chemotaxis is the sea urchin Arbacia punctulata. Resact, the chemoattractant of Arbacia, is a peptide that binds to a receptor guanylyl cyclase. The signaling pathway underlying chemotaxis is still poorly understood. Stimulation of sperm with resact induces a variety of cellular events, including a rise in intracellular pH (pHi) and an influx of Ca2+; the Ca2+ entry is essential for the chemotactic behavior. Previous studies proposed that the influx of Ca2+ is initiated by the rise in pHi. According to this proposal, a cGMP-induced hyperpolarization activates a voltage-dependent Na+/H+ exchanger that expels H+ from the cell. Because some aspects of the proposed signaling pathway are inconsistent with recent results (Kaupp, U.B., J. Solzin, J.E. Brown, A. Helbig, V. Hagen, M. Beyermann, E. Hildebrand, and I. Weyand. 2003. Nat. Cell Biol. 5:109–117), we reexamined the role of protons in chemotaxis of sperm using kinetic measurements of the changes in pHi and intracellular Ca2+ concentration. We show that for physiological concentrations of resact (<25 pM), the influx of Ca2+ precedes the rise in pHi. Moreover, buffering of pHi completely abolishes the resact-induced pHi signal, but leaves the Ca2+ signal and the chemotactic motor response unaffected. We conclude that an elevation of pHi is required neither to open Ca2+-permeable channels nor to control the chemotactic behavior. Intracellular release of cGMP from a caged compound does not cause an increase in pHi, indicating that the rise in pHi is induced by cellular events unrelated to cGMP itself, but probably triggered by the consumption and subsequent replenishment of GTP. These results show that the resact-induced rise in pHi is not an obligatory step in sperm chemotactic signaling. A rise in pHi is also not required for peptide-induced Ca2+ entry into sperm of the sea urchin Strongylocentrotus purpuratus. Speract, a peptide of S. purpuratus may act as a chemoattractant as well or may serve functions other than chemotaxis.

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Calcium uptake and release by isolated cortices and microsomes from the unfertilized egg of the sea urchin Strongylocentrotus droebachiensis.

The Journal of Cell Biology ◽

10.1083/jcb.102.6.2205 ◽

1986 ◽

Vol 102 (6) ◽

pp. 2205-2210 ◽

Cited By ~ 42

Author(s):

J A Oberdorf ◽

J F Head ◽

B Kaminer

Keyword(s):

Sea Urchin ◽

Calcium Uptake ◽

Inositol Trisphosphate ◽

Calcium Ionophore ◽

Strongylocentrotus Droebachiensis ◽

Cortical Granule ◽

Free Calcium ◽

Cortical Region ◽

Ionophore A23187 ◽

Dependent Manner

Isolated cortices from unfertilized sea urchin eggs sequester calcium in an ATP-dependent manner when incubated in a medium containing free calcium levels characteristic of the resting cell (approximately 0.1 microM). This ATP-dependent calcium uptake activity was measured in the presence of 5 mM Na azide to prevent mitochondrial accumulation, was increased by oxalate, and was blocked by 150 microM quercetin and 50 microM vanadate (known inhibitors of calcium uptake into the sarcoplasmic reticulum). Cortical regions preloaded with 45Ca in the presence of ATP were shown to dramatically increase their rate of calcium efflux upon the addition of (a) the calcium ionophore A23187 (10 microM), (b) trifluoperazine (200 microM), (c) concentrations of free calcium that activated cortical granule exocytosis, and (d) the calcium mobilizing agent inositol trisphosphate. This pool of calcium is most likely sequestered in the portion of the egg's endoplasmic reticulum that remains associated with the cortical region during its isolation. We have developed a method for obtaining a high yield of purified microsomal vesicles from whole eggs. This preparation also demonstrates ATP-dependent calcium sequestering activity which increases in the presence of oxalate and has similar sensitivities to calcium transport inhibitors; however, the isolated microsomal vesicles did not show any detectable release of calcium when exposed to inositol trisphosphate.

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