scholarly journals Inhibiting actin polymerization does not prevent the fast block to polyspermy in the African clawed frog, Xenopus laevis

2020 ◽  
Author(s):  
Maiwase Tembo ◽  
Monica L. Sauer ◽  
Bennett W. Wisner ◽  
David O. Beleny ◽  
Marc A. Napolitano ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Actin Polymerization ◽  
Sea Urchins ◽  
African Clawed Frog ◽  
Successful Reproduction ◽  
Sperm Entry ◽  
Egg Membrane ◽  
Clawed Frog

AbstractFertilization of an egg by more than one sperm presents one of the earliest and most prevalent obstacles to successful reproduction. As such, eggs employ multiple mechanisms to prevent sperm entry into the nascent zygote. The fast block to polyspermy is a depolarization of the egg membrane initiated by sperm entry and is employed by diverse external fertilizers including frogs and sea urchins. For some external fertilizers, sperm entry is associated with actin polymerization during the initiation of the fast block. We therefore sought to determine whether the fast block to polyspermy in the African clawed frog, Xenopus laevis, requires actin polymerization. Although actin polymerization is required for sperm entry into eggs from diverse external fertilizers, including sea urchins and zebrafish, here we demonstrate that actin polymerization is not required for the fast block to polyspermy in X. laevis.

scholarly journals The TMEM16A channel mediates the fast polyspermy block in Xenopus laevis

2018 ◽  
Vol 150 (9) ◽  
pp. 1249-1259 ◽  
Author(s):  
Katherine L. Wozniak ◽  
Wesley A. Phelps ◽  
Maiwase Tembo ◽  
Miler T. Lee ◽  
Anne E. Carlson
Keyword(s):  
Xenopus Laevis ◽  
Sea Urchins ◽  
Transmembrane Protein ◽  
Sequencing Data ◽  
African Clawed Frog ◽  
Cl Channels ◽  
Whole Cell Recordings ◽  
Clawed Frog ◽  
Effect Of Inhibitors ◽  
Event Triggered

In externally fertilizing animals, such as sea urchins and frogs, prolonged depolarization of the egg immediately after fertilization inhibits the entry of additional sperm—a phenomenon known as the fast block to polyspermy. In the African clawed frog Xenopus laevis, this depolarization is driven by Ca2+-activated Cl− efflux. Although the prominent Ca2+-activated Cl− currents generated in immature X. laevis oocytes are mediated by X. laevis transmembrane protein 16a (xTMEM16A) channels, little is known about the channels that contribute to the fast block in mature eggs. Moreover, the gamete undergoes a gross transformation as it develops from an immature oocyte into a fertilization-competent egg. Here, we report the results of our approach to identify the Ca2+-activated Cl− channel that triggers the fast block. By querying published proteomic and RNA-sequencing data, we identify two Ca2+-activated Cl− channels expressed in fertilization-competent X. laevis eggs: xTMEM16A and X. laevis bestrophin 2A (xBEST2A). By exogenously expressing xTMEM16A and xBEST2A in axolotl cells lacking endogenous Ca2+-activated currents, we characterize the effect of inhibitors on currents mediated by these channels. None of the inhibitors tested block xBEST2A currents specifically. However, 2-(4-chloro-2-methylphenoxy)-N-[(2-methoxyphenyl)methylideneamino]-acetamide (Ani9) and N-((4-methoxy)-2-naphthyl)-5-nitroanthranilic acid (MONNA) each reduce xTMEM16A currents by more than 70% while only nominally inhibiting those generated by xBEST2A. Using whole-cell recordings during fertilization, we find that Ani9 and MONNA effectively diminish fertilization-evoked depolarizations. Additionally, these inhibitors lead to increased polyspermy in X. laevis embryos. These results indicate that fertilization activates TMEM16A channels in X. laevis eggs and induces the earliest known event triggered by fertilization: the fast block to polyspermy.

scholarly journals The TMEM16A Channel Mediates the fast polyspermy block in Xenopus Laevis

2018 ◽  
Author(s):  
Katherine L. Wozniak ◽  
Wesley A. Phelps ◽  
Maiwase Tembo ◽  
Miler T. Lee ◽  
Anne E. Carlson
Keyword(s):  
Xenopus Laevis ◽  
Sea Urchins ◽  
List Type ◽  
Rna Seq ◽  
Whole Cell ◽  
African Clawed Frog ◽  
Pharmacologic Inhibitors ◽  
Whole Cell Recordings ◽  
Clawed Frog ◽  
Event Triggered

ABSTRACTIn externally fertilizing animals, such as sea urchins and frogs, prolonged depolarization of the egg immediately after fertilization inhibits the entry of additional sperm – a phenomenon known as the fast block to polyspermy. In the African clawed frog, Xenopus laevis, this depolarization is driven by a Ca2+-activated Cl− efflux. Although the prominent Ca2+-activated Cl− currents generated by immature X. laevis oocytes are conducted by xTMEM16A channels, little is known about which channels contribute to fertilization-competency in mature eggs. Moreover, the gamete undergoes a gross transformation as it matures from an immature oocyte into a fertilization-competent egg. Here we report the results of our approach to identify the Ca2+-activated Cl− channel that triggers the fast block. Querying published proteomics and RNA-seq data, we identified two Ca2+-activated Cl− channels expressed in fertilization-competent X. laevis eggs: xTMEM16A and xBEST2A. Furthermore, transcripts for these channels increase in abundance during gamete maturation. To determine if either of these mediates the fast block, we characterized exogenously expressed xTMEM16A and xBEST2A using pharmacologic inhibitors. None of the inhibitors tested blocked xBEST2A currents specifically. However, Ani9 and MONNA each reduced xTMEM16A currents by more than 70%, while only nominally inhibiting those generated by xBEST2A. Using whole-cell recordings during fertilization, we found that Ani9 and MONNA effectively diminished fertilization-evoked depolarizations. These results indicate that fertilization activates TMEM16A channels in X. laevis eggs and induces the earliest known event triggered by fertilization: the fast block to polyspermy.HIGHLIGHTSProtein for the channels xBEST2A and xTMEM16A is present in X. laevis eggs.The inhibitors MONNA and Ani9 effectively block xTMEM16A compared to xBEST2A.Xenopus laevis fertilization opens TMEM16A to trigger egg depolarization.The TMEM16A-mediated depolarization is critical for the fast block to polyspermy.

scholarly journals Developmental changes of purinergic control of intestinal motor activity during metamorphosis in the African clawed frog, Xenopus laevis

2007 ◽  
Vol 292 (5) ◽  
pp. R1916-R1925 ◽  
Author(s):  
Monika Sundqvist
Keyword(s):  
Xenopus Laevis ◽  
Motor Activity ◽  
Receptor Antagonist ◽  
Circular Muscle ◽  
Developmental Changes ◽  
Disulfonic Acid ◽  
Developmental Phase ◽  
African Clawed Frog ◽  
Low Concentrations ◽  
Clawed Frog

Little is known about the purinergic regulation of intestinal motor activity in amphibians. Purinergic control of intestinal motility is subject to changes during development in mammals. The aim of this study was to investigate purinergic control of intestinal smooth muscle in the amphibian Xenopus laevis and explore possible changes in this system during the developmental phase of metamorphosis. Effects of purinergic compounds on mean force and contraction frequency in intestinal circular muscle strips from prometamorphic, metamorphic, and juvenile animals were investigated. Before metamorphosis, low concentrations of ATP reduced motor activity, whereas the effects were reversed at higher concentrations. ATP-induced relaxation was not inhibited by the P2-receptor antagonist pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS) but was blocked by the ecto-nucleotidase inhibitor 6- N, N-diethyl-d-β,γ-dibromomethylene ATP ( ARL67256 ), indicating that an ATP-derived metabolite mediated the relaxation response at this stage. Adenosine induced relaxation before, during, and after metamorphosis, which was blocked by the A1-receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). The stable ATP-analog adenosine 5′-[γ-thio]-triphosphate (ATPγS) and 2-methylthioATP (2-MeSATP) elicited contractions in the circular muscle strips in prometamorphic tadpoles. However, in juvenile froglets, 2-MeSATP caused relaxation, as did ATPγS at low concentrations. The P2Y11/P2X1-receptor antagonist NF157 antagonized the ATPγS-induced relaxation. The P2X-preferring agonist α-β-methyleneadenosine 5′-triphosphate (α-β-MeATP) evoked PPADS-sensitive increases in mean force at all stages investigated. This study demonstrates the existence of an adenosine A1-like receptor mediating relaxation and a P2X-like receptor mediating contraction in the X. laevis gut before, during, and after metamorphosis. Furthermore, the development of a P2Y11-like receptor-mediated relaxation during metamorphosis is shown.

scholarly journals Toxic effects of carbendazim andn-butyl isocyanate, metabolites of the fungicide benomyl, on early development in the African clawed frog,Xenopus laevis

2008 ◽  
Vol 23 (1) ◽  
pp. 131-144 ◽  
Author(s):  
Chun-Sik Yoon ◽  
Jung-Hyo Jin ◽  
Joo-Hung Park ◽  
Chang-Yeol Yeo ◽  
Song-Ja Kim ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Early Development ◽  
Toxic Effects ◽  
African Clawed Frog ◽  
Clawed Frog

scholarly journals First parasitological study of the African clawed frog (Xenopus laevis, Amphibia) in Chile

2017 ◽  
Vol 26 (2) ◽  
pp. 243-247 ◽  
Author(s):  
Cristóbal Castillo ◽  
Gabriel Lobos ◽  
Daniel González-Acuña ◽  
Lucila Moreno ◽  
Cynthya Elizabeth González ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Introduced Species ◽  
Batrachochytrium Dendrobatidis ◽  
First Record ◽  
Central Chile ◽  
African Clawed Frog ◽  
Parasite Richness ◽  
Native Birds ◽  
Clawed Frog ◽  
Parasitological Study

Abstract Introduced species can arrive into new territories with parasites; however, these species are expected to face lower parasite richness than in their original regions. Both introduced hosts and parasites can affect native fauna. Since their release into the wild in Chile following laboratory use, Xenopus laevis Daudin, 1802 has widely spread throughout central Chile. The only pathogen described on the host is the fungus Batrachochytrium dendrobatidis Longcore, Pessier, Nichols, 1999; thus, this is the first parasitological study of this species in Chile. In 10 localities in central Chile, 179 specimens of X. laevis were captured and examined for parasites in the gastrointestinal tube, cavities, lungs, liver, and skin. Only nine specimens of the genus Contracaecum Railliet, Henry, 1912 were found in six specimens of X. laevis from a private dam in La Patagua. It is likely that these parasites originated from species of native birds. This is the first record of Contracaecum sp. in Chilean amphibians.

Sign in / Sign up

Export Citation Format

Share Document