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Xenopus
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{{Short description|Genus of amphibians}}{{Automatic taxobox| oldest_fossil = Oligocene| image = Xenopus laevis.jpg| image_caption = Xenopus laevis| taxon = Xenopus- the content below is remote from Wikipedia
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| Johann Georg Wagler>Wagler 1827| subdivision_ranks = Species | #Species>See text}}Xenopus ({{IPAc-en|ˈ|z|É›|n|É™|p|É™|s}}{{refn|ENCYCLOPEDIA,www.lexico.com/definition/Xenopus,web.archive.org/web/20200322182228/https://www.lexico.com/definition/xenopus, dead, 2020-03-22, Xenopus, Lexico UK English Dictionary, Oxford University Press, }}{{refn|{{MerriamWebsterDictionary|access-date=2016-01-21|Xenopus}}}}) (Gk., ξενος, xenos = strange, πους, pous = foot, commonly known as the clawed frog) is a genus of highly aquatic frogs native to sub-Saharan Africa. Twenty species are currently described within it. The two best-known species of this genus are Xenopus laevis and Xenopus tropicalis, which are commonly studied as model organisms for developmental biology, cell biology, toxicology, neuroscience and for modelling human disease and birth defects.JOURNAL, Nenni MJ, Fisher ME, James-Zorn C, Pells TJ, Ponferrada V, Chu S, Fortriede JD, Burns KA, Wang Y, Lotay VS, Wang DZ, Segerdell E, Chaturvedi P, Karimi K, Vize PD, Zorn AM, 6, Xenbase: Facilitating the Use of Xenopus to Model Human Disease, Frontiers in Physiology, 10, 154, 2019, 30863320, 6399412, 10.3389/fphys.2019.00154, free, JOURNAL, Wallingford JB, Liu KJ, Zheng Y, Xenopus, Current Biology, 20, 6, R263–R264, March 2010, 20334828, 10.1016/j.cub.2010.01.012, free, 2010CBio...20.R263W, JOURNAL, Harland RM, Grainger RM, Xenopus research: metamorphosed by genetics and genomics, Trends in Genetics, 27, 12, 507–515, December 2011, 21963197, 3601910, 10.1016/j.tig.2011.08.003, The genus is also known for its polyploidy, with some species having up to 12 sets of chromosomes.CharacteristicsXenopus laevis is a rather inactive creature. It is incredibly hardy and can live up to 15 years. At times the ponds that Xenopus laevis is found in dry up, compelling it, in the dry season, to burrow into the mud, leaving a tunnel for air. It may lie dormant for up to a year. If the pond dries up in the rainy season, Xenopus laevis may migrate long distances to another pond, maintaining hydration by the rains. It is an adept swimmer, swimming in all directions with ease. It is barely able to hop, but it is able to crawl. It spends most of its time underwater and comes to surface to breathe. Respiration is predominantly through its well developed lungs; there is little cutaneous respiration.DescriptionAll species of Xenopus have flattened, somewhat egg-shaped and streamlined bodies, and very slippery skin (because of a protective mucus covering).WEB,www.iacuc.arizona.edu/training/xenopus/intro.html, IACUC Learning Module — Xenopus laevis, University of Arizona, 2009-10-11, 2010-06-26,www.iacuc.arizona.edu/training/xenopus/intro.html," title="web.archive.org/web/20100626190703www.iacuc.arizona.edu/training/xenopus/intro.html,">web.archive.org/web/20100626190703www.iacuc.arizona.edu/training/xenopus/intro.html, dead, The frog’s skin is smooth, but with a lateral line sensory organ that has a stitch-like appearance. The frogs are all excellent swimmers and have powerful, fully webbed toes, though the fingers lack webbing. Three of the toes on each foot have conspicuous black claws. The frog’s eyes are on top of the head, looking upwards. The pupils are circular. They have no moveable eyelids, tongues (rather it is completely attached to the floor of the mouth) or eardrums (similarly to Pipa pipa, the common Suriname toadBOOK, Roots C, Nocturnal animals, Greenwood Press, 19, 978-0-313-33546-4, 2006, ).BOOK, Passmore NI, Carruthers VC, 1979, South African Frogs, 42–43, Witwatersrand University Press, Johannesburg, 0-85494-525-3, Unlike most amphibians, they have no haptoglobin in their blood.BehaviourXenopus species are entirely aquatic, though they have been observed migrating on land to nearby bodies of water during times of drought or in heavy rain. They are usually found in lakes, rivers, swamps, potholes in streams, and man-made reservoirs.Adult frogs are usually both predators and scavengers, and since their tongues are unusable, the frogs use their small fore limbs to aid in the feeding process. Since they also lack vocal sacs, they make clicks (brief pulses of sound) underwater (again similar to Pipa pipa). Males establish a hierarchy of social dominance in which primarily one male has the right to make the advertisement call.JOURNAL, Tobias ML, Corke A, Korsh J, Yin D, Kelley DB, Vocal competition in male Xenopus laevis frogs, Behavioral Ecology and Sociobiology, 64, 11, 1791–1803, November 2010, 21442049, 3064475, 10.1007/s00265-010-0991-3, The females of many species produce a release call, and Xenopus laevis females produce an additional call when sexually receptive and soon to lay eggs.JOURNAL, Tobias ML, Viswanathan SS, Kelley DB, Rapping, a female receptive call, initiates male-female duets in the South African clawed frog, Proceedings of the National Academy of Sciences of the United States of America, 95, 4, 1870–1875, February 1998, 9465109, 19205, 10.1073/pnas.95.4.1870, free, 1998PNAS...95.1870T, The Xenopus species are also active during the twilight (or crepuscular) hours.During breeding season, the males develop ridge-like nuptial pads (black in color) on their fingers to aid in grasping the female. The frogs’ mating embrace is inguinal, meaning the male grasps the female around her waist.Species(File:Xenopus laevis female with egg batch and Xenopus tropicalis male - journal.pbio.1001201.g001.png|thumb|A Xenopus laevis female with a batch of freshly laid eggs and a Xenopus tropicalis male)Extant species{{Div col|colwidth=30em}}
Fossil speciesThe following fossil species have been described:[ Xenopus] at Fossilworks.org
Model organism for biological researchLike many other frogs, they are often used in laboratory as research subjects. Xenopus embryos and eggs are a popular model system for a wide variety of biological studies. This animal is used because of its powerful combination of experimental tractability and close evolutionary relationship with humans, at least compared to many model organisms.Xenopus has long been an important tool for in vivo studies in molecular, cell, and developmental biology of vertebrate animals. However, the wide breadth of Xenopus research stems from the additional fact that cell-free extracts made from Xenopus are a premier in vitro system for studies of fundamental aspects of cell and molecular biology. Thus, Xenopus is a vertebrate model system that allows for high-throughput in vivo analyses of gene function and high-throughput biochemistry. Furthermore, Xenopus oocytes are a leading system for studies of ion transport and channel physiology. Xenopus is also a unique system for analyses of genome evolution and whole genome duplication in vertebrates,JOURNAL, Session AM, Uno Y, Kwon T, Chapman JA, Toyoda A, Takahashi S, Fukui A, Hikosaka A, Suzuki A, Kondo M, van Heeringen SJ, Quigley I, Heinz S, Ogino H, Ochi H, Hellsten U, Lyons JB, Simakov O, Putnam N, Stites J, Kuroki Y, Tanaka T, Michiue T, Watanabe M, Bogdanovic O, Lister R, Georgiou G, Paranjpe SS, van Kruijsbergen I, Shu S, Carlson J, Kinoshita T, Ohta Y, Mawaribuchi S, Jenkins J, Grimwood J, Schmutz J, Mitros T, Mozaffari SV, Suzuki Y, Haramoto Y, Yamamoto TS, Takagi C, Heald R, Miller K, Haudenschild C, Kitzman J, Nakayama T, Izutsu Y, Robert J, Fortriede J, Burns K, Lotay V, Karimi K, Yasuoka Y, Dichmann DS, Flajnik MF, Houston DW, Shendure J, DuPasquier L, Vize PD, Zorn AM, Ito M, Marcotte EM, Wallingford JB, Ito Y, Asashima M, Ueno N, Matsuda Y, Veenstra GJ, Fujiyama A, Harland RM, Taira M, Rokhsar DS, 6, Genome evolution in the allotetraploid frog Xenopus laevis, Nature, 538, 7625, 336–343, October 2016, 27762356, 5313049, 10.1038/nature19840, 2016Natur.538..336S, as different Xenopus species form a ploidy series formed by interspecific hybridization.JOURNAL, Schmid M, Evans BJ, Bogart JP, Polyploidy in Amphibia, Cytogenetic and Genome Research, 145, 3–4, 315–330, 2015, 26112701, 10.1159/000431388, free, In 1931, Lancelot Hogben noted that Xenopus laevis females ovulated when injected with the urine of pregnant women.JOURNAL, Hogben L, Charles E, Slome D, Studies on the pituitary. 8. The relation of the pituitary gland to calcium metabolism and ovarian function in Xenopus., Journal of Experimental Biology, 1931, 8, 345–54,jeb.biologists.org/content/8/4/345, 10.1242/jeb.8.4.345, This led to a pregnancy test that was later refined by South African researchers Hillel Abbe Shapiro and Harry Zwarenstein.JOURNAL, Elkan ER, The Xenopus Pregnancy Test, British Medical Journal, 2, 4067, 1253–1274.2, December 1938, 20781969, 2211252, 10.1136/bmj.2.4067.1253, A female Xenopus frog injected with a woman’s urine was put in a jar with a little water. If eggs were in the water a day later it meant the woman was pregnant. Four years after the first Xenopus test, Zwarenstein’s colleague, Dr Louis Bosman, reported that the test was accurate in more than 99% of cases.Diagnosis of Pregnancy, Louis P. Bosman, British Medical Journal 1937;2:939, 6 November 1937 From the 1930s to the 1950s, thousands of frogs were exported across the world for use in these pregnancy tests.MAGAZINE,www.smithsonianmag.com/smart-news/doctors-used-to-use-live-african-frogs-as-pregnancy-tests-64279275/, Doctors Used to Use Live African Frogs As Pregnancy Tests, Nuwer R, Rachel Nuwer, Smithsonian Magazine, Smithsonian.com, 16 May 2013, 30 October 2018, The {{visible anchor|National Xenopus Resource|lc=National Xenopus Resource}} of the Marine Biological Laboratory is an in vivo repository for transgenic and mutant strains and a training center.WEB, The National Xenopus Resource, Marine Biological Laboratory,www.mbl.edu/research/resources-research-facilities/national-xenopus-resource, 2022-04-05,Online Model Organism DatabaseXenbaseJOURNAL, Karimi K, Fortriede JD, Lotay VS, Burns KA, Wang DZ, Fisher ME, Pells TJ, James-Zorn C, Wang Y, Ponferrada VG, Chu S, Chaturvedi P, Zorn AM, Vize PD, 6, Xenbase: a genomic, epigenomic and transcriptomic model organism database, Nucleic Acids Research, 46, D1, D861–D868, January 2018, 29059324, 5753396, 10.1093/nar/gkx936, is the Model Organism Database (MOD) for both Xenopus laevis and Xenopus tropicalis.WEB, Xenopus model organism database,www.xenbase.org, Xenbase.org,Investigation of human disease genesAll modes of Xenopus research (embryos, cell-free extracts, and oocytes) are commonly used in direct studies of human disease genes and to study the basic science underlying initiation and progression of cancer.JOURNAL, Hardwick LJ, Philpott A, An oncologist׳s friend: How Xenopus contributes to cancer research, Developmental Biology, 408, 2, 180–187, December 2015, 25704511, 4684227, 10.1016/j.ydbio.2015.02.003, Modeling Human Development and Disease in Xenopus, Xenopus embryos for in vivo studies of human disease gene function: Xenopus embryos are large and easily manipulated, and moreover, thousands of embryos can be obtained in a single day. Indeed, Xenopus was the first vertebrate animal for which methods were developed to allow rapid analysis of gene function using misexpression (by mRNA injectionJOURNAL, Gurdon JB, Lane CD, Woodland HR, Marbaix G, Use of frog eggs and oocytes for the study of messenger RNA and its translation in living cells, Nature, 233, 5316, 177–182, September 1971, 4939175, 10.1038/233177a0, 4160808, 1971Natur.233..177G, ). Injection of mRNA in Xenopus that led to the cloning of interferon.JOURNAL, Reynolds FH, Premkumar E, Pitha PM, Interferon activity produced by translation of human interferon messenger RNA in cell-free ribosomal systems and in Xenopus oöcytes, Proceedings of the National Academy of Sciences of the United States of America, 72, 12, 4881–4885, December 1975, 1061077, 388836, 10.1073/pnas.72.12.4881, free, 1975PNAS...72.4881R, Moreover, the use of morpholino-antisense oligonucleotides for gene knockdowns in vertebrate embryos, which is now widely used, was first developed by Janet Heasman using Xenopus.JOURNAL, Heasman J, Kofron M, Wylie C, Beta-catenin signaling activity dissected in the early Xenopus embryo: a novel antisense approach, Developmental Biology, 222, 1, 124–134, June 2000, 10885751, 10.1006/dbio.2000.9720, free, In recent years, these approaches have played in important role in studies of human disease genes. The mechanism of action for several genes mutated in human cystic kidney disorders (e.g. nephronophthisis) have been extensively studied in Xenopus embryos, shedding new light on the link between these disorders, ciliogenesis and Wnt signaling.JOURNAL, Schäfer T, Pütz M, Lienkamp S, Ganner A, Bergbreiter A, Ramachandran H, Gieloff V, Gerner M, Mattonet C, Czarnecki PG, Sayer JA, Otto EA, Hildebrandt F, Kramer-Zucker A, Walz G, 6, Genetic and physical interaction between the NPHP5 and NPHP6 gene products, Human Molecular Genetics, 17, 23, 3655–3662, December 2008, 18723859, 2802281, 10.1093/hmg/ddn260, Xenopus embryos have also provided a rapid test bed for validating newly discovered disease genes. For example, studies in Xenopus confirmed and elucidated the role of PYCR1 in cutis laxa with progeroid features.JOURNAL, Reversade B, Escande-Beillard N, Dimopoulou A, Fischer B, Chng SC, Li Y, Shboul M, Tham PY, Kayserili H, Al-Gazali L, Shahwan M, Brancati F, Lee H, O’Connor BD, Schmidt-von Kegler M, Merriman B, Nelson SF, Masri A, Alkazaleh F, Guerra D, Ferrari P, Nanda A, Rajab A, Markie D, Gray M, Nelson J, Grix A, Sommer A, Savarirayan R, Janecke AR, Steichen E, Sillence D, Hausser I, Budde B, Nürnberg G, Nürnberg P, Seemann P, Kunkel D, Zambruno G, Dallapiccola B, Schuelke M, Robertson S, Hamamy H, Wollnik B, Van Maldergem L, Mundlos S, Kornak U, 6, Mutations in PYCR1 cause cutis laxa with progeroid features, Nature Genetics, 41, 9, 1016–1021, September 2009, 19648921, 10.1038/ng.413, 10221927, Transgenic Xenopus for studying transcriptional regulation of human disease genes: Xenopus embryos develop rapidly, so transgenesis in Xenopus is a rapid and effective method for analyzing genomic regulatory sequences. In a recent study, mutations in the SMAD7 locus were revealed to associate with human colorectal cancer. The mutations lay in conserved, but noncoding sequences, suggesting these mutations impacted the patterns of SMAD7 transcription. To test this hypothesis, the authors used Xenopus transgenesis, and revealed this genomic region drove expression of GFP in the hindgut. Moreover, transgenics made with the mutant version of this region displayed substantially less expression in the hindgut.JOURNAL, Pittman AM, Naranjo S, Webb E, Broderick P, Lips EH, van Wezel T, Morreau H, Sullivan K, Fielding S, Twiss P, Vijayakrishnan J, Casares F, Qureshi M, Gómez-Skarmeta JL, Houlston RS, 6, The colorectal cancer risk at 18q21 is caused by a novel variant altering SMAD7 expression, Genome Research, 19, 6, 987–993, June 2009, 19395656, 2694486, 10.1101/gr.092668.109, Xenopus cell-free extracts for biochemical studies of proteins encoded by human disease genes: A unique advantage of the Xenopus system is that cytosolic extracts contain both soluble cytoplasmic and nuclear proteins (including chromatin proteins). This is in contrast to cellular extracts prepared from somatic cells with already distinct cellular compartments. Xenopus egg extracts have provided numerous insights into the basic biology of cells with particular impact on cell division and the DNA transactions associated with it (see below).Studies in Xenopus egg extracts have also yielded critical insights into the mechanism of action of human disease genes associated with genetic instability and elevated cancer risk, such as ataxia telangiectasia, BRCA1 inherited breast and ovarian cancer, Nbs1 Nijmegen breakage syndrome, RecQL4 Rothmund-Thomson syndrome, c-Myc oncogene and FANC proteins (Fanconi anemia).JOURNAL, Joukov V, Groen AC, Prokhorova T, Gerson R, White E, Rodriguez A, Walter JC, Livingston DM, 6, The BRCA1/BARD1 heterodimer modulates ran-dependent mitotic spindle assembly, Cell, 127, 3, 539–552, November 2006, 17081976, 10.1016/j.cell.2006.08.053, 17769149, free, JOURNAL, You Z, Bailis JM, Johnson SA, Dilworth SM, Hunter T, Rapid activation of ATM on DNA flanking double-strand breaks, Nature Cell Biology, 9, 11, 1311–1318, November 2007, 17952060, 10.1038/ncb1651, 17389213, JOURNAL, Ben-Yehoyada M, Wang LC, Kozekov ID, Rizzo CJ, Gottesman ME, Gautier J, Checkpoint signaling from a single DNA interstrand crosslink, Molecular Cell, 35, 5, 704–715, September 2009, 19748363, 2756577, 10.1016/j.molcel.2009.08.014, JOURNAL, Sobeck A, Stone S, Landais I, de Graaf B, Hoatlin ME, The Fanconi anemia protein FANCM is controlled by FANCD2 and the ATR/ATM pathways, The Journal of Biological Chemistry, 284, 38, 25560–25568, September 2009, 19633289, 2757957, 10.1074/jbc.M109.007690, free, JOURNAL, Dominguez-Sola D, Ying CY, Grandori C, Ruggiero L, Chen B, Li M, Galloway DA, Gu W, Gautier J, Dalla-Favera R, 6, Non-transcriptional control of DNA replication by c-Myc, Nature, 448, 7152, 445–451, July 2007, 17597761, 10.1038/nature05953, 4422771, 2007Natur.448..445D, Xenopus oocytes for studies of gene expression and channel activity related to human disease: Yet another strength of Xenopus is the ability to rapidly and easily assay the activity of channel and transporter proteins using expression in oocytes. This application has also led to important insights into human disease, including studies related to trypanosome transmission,JOURNAL, Dean S, Marchetti R, Kirk K, Matthews KR, A surface transporter family conveys the trypanosome differentiation signal, Nature, 459, 7244, 213–217, May 2009, 19444208, 2685892, 10.1038/nature07997, 2009Natur.459..213D, Epilepsy with ataxia and sensorineural deafnessJOURNAL, Bockenhauer D, Feather S, Stanescu HC, Bandulik S, Zdebik AA, Reichold M, Tobin J, Lieberer E, Sterner C, Landoure G, Arora R, Sirimanna T, Thompson D, Cross JH, van’t Hoff W, Al Masri O, Tullus K, Yeung S, Anikster Y, Klootwijk E, Hubank M, Dillon MJ, Heitzmann D, Arcos-Burgos M, Knepper MA, Dobbie A, Gahl WA, Warth R, Sheridan E, Kleta R, 6, Epilepsy, ataxia, sensorineural deafness, tubulopathy, and KCNJ10 mutations, The New England Journal of Medicine, 360, 19, 1960–1970, May 2009, 19420365, 3398803, 10.1056/NEJMoa0810276, Catastrophic cardiac arrhythmia (Long-QT syndrome)JOURNAL, Gustina AS, Trudeau MC, A recombinant N-terminal domain fully restores deactivation gating in N-truncated and long QT syndrome mutant hERG potassium channels, Proceedings of the National Academy of Sciences of the United States of America, 106, 31, 13082–13087, August 2009, 19651618, 2722319, 10.1073/pnas.0900180106, free, 2009PNAS..10613082G, and Megalencephalic leukoencephalopathy.JOURNAL, Duarri A, Teijido O, López-Hernández T, Scheper GC, Barriere H, Boor I, Aguado F, Zorzano A, PalacÃn M, MartÃnez A, Lukacs GL, van der Knaap MS, Nunes V, Estévez R, 6, Molecular pathogenesis of megalencephalic leukoencephalopathy with subcortical cysts: mutations in MLC1 cause folding defects, Human Molecular Genetics, 17, 23, 3728–3739, December 2008, 18757878, 2581428, 10.1093/hmg/ddn269, Gene editing by the CRISPR/CAS system has recently been demonstrated in Xenopus tropicalisJOURNAL, Blitz IL, Biesinger J, Xie X, Cho KW, Biallelic genome modification in F(0) Xenopus tropicalis embryos using the CRISPR/Cas system, Genesis, 51, 12, 827–834, December 2013, 24123579, 4039559, 10.1002/dvg.22719, JOURNAL, Nakayama T, Fish MB, Fisher M, Oomen-Hajagos J, Thomsen GH, Grainger RM, Simple and efficient CRISPR/Cas9-mediated targeted mutagenesis in Xenopus tropicalis, Genesis, 51, 12, 835–843, December 2013, 24123613, 3947545, 10.1002/dvg.22720, and Xenopus laevis.JOURNAL, Wang F, Shi Z, Cui Y, Guo X, Shi YB, Chen Y, Targeted gene disruption in Xenopus laevis using CRISPR/Cas9, En, Cell & Bioscience, 5, 1, 15, 2015-04-14, 25897376, 4403895, 10.1186/s13578-015-0006-1, free, This technique is being used to screen the effects of human disease genes in Xenopus and the system is sufficiently efficient to study the effects within the same embryos that have been manipulated.JOURNAL, Bhattacharya D, Marfo CA, Li D, Lane M, Khokha MK, CRISPR/Cas9: An inexpensive, efficient loss of function tool to screen human disease genes in Xenopus, Developmental Biology, 408, 2, 196–204, December 2015, 26546975, 4684459, 10.1016/j.ydbio.2015.11.003, Modeling Human Development and Disease in Xenopus,Investigation of fundamental biological processesSignal transduction: Xenopus embryos and cell-free extracts are widely used for basic research in signal transduction. In just the last few years, Xenopus embryos have provided crucial insights into the mechanisms of TGF-beta and Wnt signal transduction. For example, Xenopus embryos were used to identify the enzymes that control ubiquitination of Smad4,JOURNAL, Dupont S, Mamidi A, Cordenonsi M, Montagner M, Zacchigna L, Adorno M, Martello G, Stinchfield MJ, Soligo S, Morsut L, Inui M, Moro S, Modena N, Argenton F, Newfeld SJ, Piccolo S, 6, FAM/USP9x, a deubiquitinating enzyme essential for TGFbeta signaling, controls Smad4 monoubiquitination, Cell, 136, 1, 123–135, January 2009, 19135894, 10.1016/j.cell.2008.10.051, 16458957, free, and to demonstrate direct links between TGF-beta superfamily signaling pathways and other important networks, such as the MAP kinase pathwayJOURNAL, Cordenonsi M, Montagner M, Adorno M, Zacchigna L, Martello G, Mamidi A, Soligo S, Dupont S, Piccolo S, 6, Integration of TGF-beta and Ras/MAPK signaling through p53 phosphorylation, Science, 315, 5813, 840–843, February 2007, 17234915, 10.1126/science.1135961, 83962686, 2007Sci...315..840C, free, and the Wnt pathway.JOURNAL, Fuentealba LC, Eivers E, Ikeda A, Hurtado C, Kuroda H, Pera EM, De Robertis EM, Integrating patterning signals: Wnt/GSK3 regulates the duration of the BMP/Smad1 signal, Cell, 131, 5, 980–993, November 2007, 18045539, 2200633, 10.1016/j.cell.2007.09.027, Moreover, new methods using egg extracts revealed novel, important targets of the Wnt/GSK3 destruction complex.JOURNAL, Kim NG, Xu C, Gumbiner BM, Identification of targets of the Wnt pathway destruction complex in addition to beta-catenin, Proceedings of the National Academy of Sciences of the United States of America, 106, 13, 5165–5170, March 2009, 19289839, 2663984, 10.1073/pnas.0810185106, free, 2009PNAS..106.5165K, Cell division: Xenopus egg extracts have allowed the study of many complicated cellular events in vitro. Because egg cytosol can support successive cycling between mitosis and interphase in vitro, it has been critical to diverse studies of cell division. For example, the small GTPase Ran was first found to regulate interphase nuclear transport, but Xenopus egg extracts revealed the critical role of Ran GTPase in mitosis independent of its role in interphase nuclear transport.JOURNAL, Kaláb P, Pralle A, Isacoff EY, Heald R, Weis K, Analysis of a RanGTP-regulated gradient in mitotic somatic cells, Nature, 440, 7084, 697–701, March 2006, 16572176, 10.1038/nature04589, 4398374, 2006Natur.440..697K, Similarly, the cell-free extracts were used to model nuclear envelope assembly from chromatin, revealing the function of RanGTPase in regulating nuclear envelope reassembly after mitosis.JOURNAL, Tsai MY, Wang S, Heidinger JM, Shumaker DK, Adam SA, Goldman RD, Zheng Y, A mitotic lamin B matrix induced by RanGTP required for spindle assembly, Science, 311, 5769, 1887–1893, March 2006, 16543417, 10.1126/science.1122771, 12219529, 2006Sci...311.1887T, More recently, using Xenopus egg extracts, it was possible to demonstrate the mitosis-specific function of the nuclear lamin B in regulating spindle morphogenesisJOURNAL, Ma L, Tsai MY, Wang S, Lu B, Chen R, Yates JR, Zhu X, Zheng Y, 6, Requirement for Nudel and dynein for assembly of the lamin B spindle matrix, Nature Cell Biology, 11, 3, 247–256, March 2009, 19198602, 2699591, 10.1038/ncb1832, and to identify new proteins that mediate kinetochore attachment to microtubules.JOURNAL, Emanuele MJ, Stukenberg PT, Xenopus Cep57 is a novel kinetochore component involved in microtubule attachment, Cell, 130, 5, 893–905, September 2007, 17803911, 10.1016/j.cell.2007.07.023, 17520550, free, Cell-free systems have recently become practical investigatory tools, and Xenopus oocytes are often the source of the extracts used. This has produced significant results in understanding mitotic oscillation and microtubules.JOURNAL, Noireaux V, Liu AP, The New Age of Cell-Free Biology, Annual Review of Biomedical Engineering, 22, 1, 51–77, June 2020, 32151150, 10.1146/annurev-bioeng-092019-111110, Annual Reviews (publisher), Annual Reviews, 212652742, free, Embryonic development: Xenopus embryos are widely used in developmental biology. A summary of recent advances made by Xenopus research in recent years would include:
Small molecule screens to develop novel therapiesBecause huge amounts of material are easily obtained, all modalities of Xenopus research are now being used for small-molecule based screens.Chemical genetics of vascular growth in Xenopus tadpoles: Given the important role of neovascularization in cancer progression, Xenopus embryos were recently used to identify new small molecules inhibitors of blood vessel growth. Notably, compounds identified in Xenopus were effective in mice.JOURNAL, Kälin RE, Bänziger-Tobler NE, Detmar M, Brändli AW, An in vivo chemical library screen in Xenopus tadpoles reveals novel pathways involved in angiogenesis and lymphangiogenesis, Blood, 114, 5, 1110–1122, July 2009, 19478043, 2721788, 10.1182/blood-2009-03-211771, JOURNAL, Ny A, Koch M, Vandevelde W, Schneider M, Fischer C, Diez-Juan A, Neven E, Geudens I, Maity S, Moons L, Plaisance S, Lambrechts D, Carmeliet P, Dewerchin M, 6, Role of VEGF-D and VEGFR-3 in developmental lymphangiogenesis, a chemicogenetic study in Xenopus tadpoles, Blood, 112, 5, 1740–1749, September 2008, 18474726, 10.1182/blood-2007-08-106302, 14663578, free, Notably, frog embryos figured prominently in a study that used evolutionary principles to identify a novel vascular disrupting agent that may have chemotherapeutic potential.JOURNAL, Cha HJ, Byrom M, Mead PE, Ellington AD, Wallingford JB, Marcotte EM, Evolutionarily repurposed networks reveal the well-known antifungal drug thiabendazole to be a novel vascular disrupting agent, PLOS Biology, 10, 8, e1001379, 2012-01-01, 22927795, 3423972, 10.1371/journal.pbio.1001379, free, That work was featured in the New York Times Science TimesNEWS, Gene Tests in Yeast Aid Work on Cancer,www.nytimes.com/2012/08/21/health/research/clues-to-fighting-cancer-are-found-in-the-genes-of-yeast.html, The New York Times, 2012-08-21, Zimmer C, In vivo testing of potential endocrine disruptors in transgenic Xenopus embryos; A high-throughput assay for thyroid disruption has recently been developed using transgenic Xenopus embryos.JOURNAL, Fini JB, Le Mevel S, Turque N, Palmier K, Zalko D, Cravedi JP, Demeneix BA, An in vivo multiwell-based fluorescent screen for monitoring vertebrate thyroid hormone disruption, Environmental Science & Technology, 41, 16, 5908–5914, August 2007, 17874805, 10.1021/es0704129, 2007EnST...41.5908F, Small molecule screens in Xenopus egg extracts: Egg extracts provide ready analysis of molecular biological processes and can rapidly screened. This approach was used to identify novel inhibitors of proteasome-mediated protein degradation and DNA repair enzymes.JOURNAL, Dupré A, Boyer-Chatenet L, Sattler RM, Modi AP, Lee JH, Nicolette ML, Kopelovich L, Jasin M, Baer R, Paull TT, Gautier J, A forward chemical genetic screen reveals an inhibitor of the Mre11-Rad50-Nbs1 complex, Nature Chemical Biology, 4, 2, 119–25, February 2008, 18176557, 3065498, 10.1038/nchembio.63, JOURNAL, Landais I, Sobeck A, Stone S, LaChapelle A, Hoatlin ME, A novel cell-free screen identifies a potent inhibitor of the Fanconi anemia pathway, International Journal of Cancer, 124, 4, 783–92, February 2009, 19048618, 10.1002/ijc.24039, 33589304, free,Genetic studiesWhile Xenopus laevis is the most commonly used species for developmental biology studies, genetic studies, especially forward genetic studies, can be complicated by their pseudotetraploid genome. Xenopus tropicalis provides a simpler model for genetic studies, having a diploid genome.Gene expression knockdown techniquesThe expression of genes can be reduced by a variety of means, for example by using antisense oligonucleotides targeting specific mRNA molecules. DNA oligonucleotides complementary to specific mRNA molecules are often chemically modified to improve their stability in vivo. The chemical modifications used for this purpose include phosphorothioate, 2’-O-methyl, morpholino, MEA phosphoramidate and DEED phosphoramidate.JOURNAL, Dagle JM, Weeks DL, Oligonucleotide-based strategies to reduce gene expression, Differentiation; Research in Biological Diversity, 69, 2–3, 75–82, December 2001, 11798068, 10.1046/j.1432-0436.2001.690201.x,Morpholino oligonucleotidesMorpholino oligos are used in both X. laevis and X. tropicalis to probe the function of a protein by observing the results of eliminating the protein’s activity.JOURNAL, Blum M, De Robertis EM, Wallingford JB, Niehrs C, Morpholinos: Antisense and Sensibility, Developmental Cell, 35, 2, 145–149, October 2015, 26506304, 10.1016/j.devcel.2015.09.017, free, For example, a set of X. tropicalis genes has been screened in this fashion.JOURNAL, Rana AA, Collart C, Gilchrist MJ, Smith JC, Defining synphenotype groups in Xenopus tropicalis by use of antisense morpholino oligonucleotides, PLOS Genetics, 2, 11, e193, November 2006, 17112317, 1636699, 10.1371/journal.pgen.0020193, free, WEB,www.gurdon.cam.ac.uk/~smithlab/screens/Xenopus-morpholino-pilot/, A Xenopus tropicalis antisense morpholino screen, 4 March 2014, Gurdon Institute, 17 January 2007, 12 June 2018,web.archive.org/web/20180612164223/https://www.gurdon.cam.ac.uk/~smithlab/screens/Xenopus-morpholino-pilot/, dead, Morpholino oligos (MOs) are short, antisense oligos made of modified nucleotides. MOs can knock down gene expression by inhibiting mRNA translation, blocking RNA splicing, or inhibiting miRNA activity and maturation. MOs have proven to be effective knockdown tools in developmental biology experiments and RNA-blocking reagents for cells in culture. MOs do not degrade their RNA targets, but instead act via a steric blocking mechanism RNAseH-independent manner. They remain stable in cells and do not induce immune responses. Microinjection of MOs in early Xenopus embryos can suppress gene expression in a targeted manner.Like all antisense approaches, different MOs can have different efficacy, and may cause off-target, non-specific effects. Often, several MOs need to be tested to find an effective target sequence. Rigorous controls are used to demonstrate specificity, including:
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