Wikipedia

Xenopus

Xenopus(/ˈzɛnəpəs/[1][2]) (Gk., ξενος,xenos= strange, πους,pous= foot, commonly known as theclawed frog) is agenusof highly aquaticfrogsnative tosub-Saharan Africa.Twenty species are currently described within it. The two best-known species of this genus areXenopus laevisandXenopus tropicalis,which are commonly studied asmodel organismsfor developmental biology, cell biology, toxicology, neuroscience and for modelling human disease and birth defects.[3][4][5]

Xenopus
Temporal range:Oligocene–Recent
Xenopus laevis
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Pipidae
Genus: Xenopus
Wagler1827
Species

See text

The genus is also known for itspolyploidy,with some species having up to 12 sets ofchromosomes.

Characteristics

edit

Xenopus laevisis a rather inactive creature. It is incredibly hardy and can live up to 15 years. At times the ponds thatXenopus laevisis 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 laevismay 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.

Description

edit

All species ofXenopushave flattened, somewhat egg-shaped and streamlined bodies, and very slippery skin (because of a protective mucus covering).[6]The frog's skin is smooth, but with alateral linesensory 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 blackclaws.

The frog's eyes are on top of the head, looking upwards. Thepupilsare circular. They have no moveableeyelids,tongues(rather it is completely attached to the floor of the mouth[6]) oreardrums(similarly toPipa pipa,the common Suriname toad[7]).[8]

Unlike most amphibians, they have nohaptoglobinin theirblood.[8]

Behaviour

edit

Xenopusspecies are entirelyaquatic,though they have been observed migrating on land to nearby bodies of water during times ofdroughtor in heavy rain. They are usually found inlakes,rivers,swamps,potholes in streams, and man-made reservoirs.[8]

Adult frogs are usually bothpredatorsandscavengers,and since their tongues are unusable, the frogs use their small fore limbs to aid in the feeding process. Since they also lackvocal sacs,they make clicks (brief pulses of sound) underwater (again similar toPipa pipa).[7]Males establish a hierarchy of social dominance in which primarily one male has the right to make the advertisement call.[9]The females of many species produce a release call, andXenopus laevisfemales produce an additional call when sexually receptive and soon to lay eggs.[10]TheXenopusspecies are also active during the twilight (orcrepuscular) hours.[8]

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.[8]

Species

edit
AXenopus laevisfemale with a batch of freshly laid eggs and aXenopus tropicalismale

Extant species

edit

Fossil species

edit

The following fossil species have been described:[11]

Model organism for biological research

edit

Like many otherfrogs,they are often used in laboratory as research subjects.[6]Xenopusembryos and eggs are a popular model system for a wide variety of biological studies.[4][5]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.[4][5]

Xenopushas long been an important tool forin vivo studiesin molecular, cell, and developmental biology of vertebrate animals.[5]However, the wide breadth ofXenopusresearch stems from the additional fact thatcell-free extractsmade fromXenopusare a premierin vitrosystem for studies of fundamental aspects of cell and molecular biology. Thus,Xenopusis a vertebrate model system that allows for high-throughputin vivoanalyses of gene function and high-throughput biochemistry. Furthermore,Xenopusoocytes are a leading system for studies of ion transport and channel physiology.[4]Xenopusis also a unique system for analyses of genome evolution and whole genome duplication in vertebrates,[12]as differentXenopusspecies form aploidyseries formed byinterspecific hybridization.[13]

In 1931,Lancelot Hogbennoted thatXenopus laevisfemales ovulated when injected with the urine of pregnant women.[14]This led to a pregnancy test that was later refined by South African researchersHillel Abbe Shapiroand Harry Zwarenstein.[15]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 firstXenopustest, Zwarenstein's colleague, Dr Louis Bosman, reported that the test was accurate in more than 99% of cases.[16]From the 1930s to the 1950s, thousands of frogs were exported across the world for use in these pregnancy tests.[17]

TheNational Xenopus Resourceof theMarine Biological Laboratoryis anin vivorepository for transgenic and mutant strains and a training center.[18]

Online Model Organism Database

edit

Xenbase[19]is theModel Organism Database (MOD)for bothXenopus laevisandXenopus tropicalis.[20]

Investigation of human disease genes

edit

All modes ofXenopusresearch (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.[21]Xenopusembryos forin vivostudies of human disease gene function:Xenopusembryos are large and easily manipulated, and moreover, thousands of embryos can be obtained in a single day. Indeed,Xenopuswas the first vertebrate animal for which methods were developed to allow rapid analysis of gene function using misexpression (by mRNA injection[22]). Injection of mRNA inXenopusthat led to the cloning of interferon.[23]Moreover, the use of morpholino-antisense oligonucleotides for gene knockdowns in vertebrate embryos, which is now widely used, was first developed by Janet Heasman usingXenopus.[24]

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 inXenopusembryos, shedding new light on the link between these disorders,ciliogenesisandWnt signaling.[25]Xenopusembryos have also provided a rapid test bed for validating newly discovered disease genes. For example, studies inXenopusconfirmed and elucidated the role ofPYCR1incutis laxawith progeroid features.[26]

TransgenicXenopusfor studying transcriptional regulation of human disease genes:Xenopusembryos develop rapidly, so transgenesis inXenopusis a rapid and effective method for analyzing genomic regulatory sequences. In a recent study, mutations in theSMAD7locus were revealed to associate with humancolorectal cancer.The mutations lay in conserved, but noncoding sequences, suggesting these mutations impacted the patterns ofSMAD7transcription. To test this hypothesis, the authors usedXenopustransgenesis, and revealed this genomic region drove expression ofGFPin the hindgut. Moreover, transgenics made with the mutant version of this region displayed substantially less expression in the hindgut.[27]

Xenopuscell-free extracts for biochemical studies of proteins encoded by human disease genes: A unique advantage of theXenopussystem 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.Xenopusegg 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 inXenopusegg 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,BRCA1inherited breast and ovarian cancer,Nbs1Nijmegen breakage syndrome,RecQL4Rothmund-Thomson syndrome,c-Myconcogene and FANC proteins (Fanconi anemia).[28][29][30][31][32]

Xenopusoocytes for studies of gene expression and channel activity related to human disease: Yet another strength ofXenopusis 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 totrypanosometransmission,[33]Epilepsywithataxiaandsensorineural deafness[34]Catastrophiccardiac arrhythmia(Long-QT syndrome)[35]and Megalencephalic leukoencephalopathy.[36]

Gene editing by the CRISPR/CAS system has recently been demonstrated inXenopustropicalis[37][38]andXenopus laevis.[39]This technique is being used to screen the effects of human disease genes inXenopusand the system is sufficiently efficient to study the effects within the same embryos that have been manipulated.[40]

Investigation of fundamental biological processes

edit

Signal transduction:Xenopusembryos and cell-free extracts are widely used for basic research in signal transduction. In just the last few years,Xenopusembryos have provided crucial insights into the mechanisms of TGF-beta and Wnt signal transduction. For example,Xenopusembryos were used to identify the enzymes that control ubiquitination of Smad4,[41]and to demonstrate direct links between TGF-beta superfamily signaling pathways and other important networks, such as the MAP kinase pathway[42]and the Wnt pathway.[43]Moreover, new methods using egg extracts revealed novel, important targets of the Wnt/GSK3 destruction complex.[44]

Cell division:Xenopusegg extracts have allowed the study of many complicated cellular eventsin vitro.Because egg cytosol can support successive cycling between mitosis and interphasein 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, butXenopusegg extracts revealed the critical role of Ran GTPase in mitosis independent of its role in interphase nuclear transport.[45]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.[46]More recently, usingXenopusegg extracts, it was possible to demonstrate the mitosis-specific function of the nuclear lamin B in regulating spindle morphogenesis[47]and to identify new proteins that mediate kinetochore attachment to microtubules.[48]Cell-free systemshave recently become practical investigatory tools, andXenopusoocytes are often the source of the extracts used. This has produced significant results in understandingmitoticoscillation andmicrotubules.[49]

Embryonic development:Xenopusembryos are widely used in developmental biology. A summary of recent advances made byXenopusresearch in recent years would include:

  1. Epigeneticsof cell fate specification[50]and epigenome reference maps[51]
  2. microRNAin germ layer patterning and eye development[52][53]
  3. Link betweenWnt signalingandtelomerase[54]
  4. Development of thevasculature[55]
  5. Gut morphogenesis[56]
  6. Contact inhibition andneural crestcell migration[57]and the generation of neural crest from pluripotent blastula cells[58]
  7. Developmental fate- Role ofNotch:Dorsky et al 1995 elucidated a pattern of expression followed by downregulation[59]

DNA replication:Xenopuscell-free extracts also support the synchronous assembly and the activation of origins of DNA replication. They have been instrumental in characterizing the biochemical function of the prereplicative complex, including MCM proteins.[60][61]

DNA damageresponse: Cell-free extracts have been instrumental to unravel the signaling pathways activated in response to DNA double-strand breaks (ATM), replication fork stalling (ATR) or DNA interstrand crosslinks (FA proteins and ATR). Notably, several mechanisms and components of these signal transduction pathways were first identified inXenopus.[30][62][63]

Apoptosis:Xenopusoocytes provide a tractable model for biochemical studies of apoptosis. Recently, oocytes were used recently to study the biochemical mechanisms of caspase-2 activation; importantly, this mechanism turns out to be conserved in mammals.[64]

Regenerative medicine:In recent years, tremendous interest in developmental biology has been stoked by the promise of regenerative medicine.Xenopushas played a role here, as well. For example, expression of seven transcription factors in pluripotentXenopuscells rendered those cells able to develop into functional eyes when implanted intoXenopusembryos, providing potential insights into the repair of retinal degeneration or damage.[65]In a vastly different study,Xenopusembryos was used to study the effects of tissue tension on morphogenesis,[66]an issue that will be critical forin vitrotissue engineering.Xenopusspecies are important model organisms for the study of spinal cord regeneration, because while capable of regeneration in their larval stages,Xenopuslose this capacity in early metamorphosis.[67]

Physiology:The directional beating of multiciliated cells is essential to development and homeostasis in the central nervous system, the airway, and the oviduct. The multiciliated cells of theXenopusepidermis have recently been developed as the firstin vivotest-bed for live-cell studies of such ciliated tissues, and these studies have provided important insights into the biomechanical and molecular control of directional beating.[68][69]

Actin:Another result from cell-freeXenopusoocyte extracts has been improved understanding of actin.[49]

Small molecule screens to develop novel therapies

edit

Because huge amounts of material are easily obtained, all modalities ofXenopusresearch are now being used for small-molecule based screens.

Chemical geneticsof vascular growth inXenopustadpoles: Given the important role of neovascularization in cancer progression,Xenopusembryos were recently used to identify new small molecules inhibitors of blood vessel growth. Notably, compounds identified inXenopuswere effective in mice.[70][71]Notably, frog embryos figured prominently in a study that used evolutionary principles to identify a novel vascular disrupting agent that may have chemotherapeutic potential.[72]That work was featured in the New York Times Science Times[73]

In vivotesting of potentialendocrine disruptorsin transgenicXenopusembryos; A high-throughput assay for thyroid disruption has recently been developed using transgenicXenopusembryos.[74]

Small molecule screens inXenopusegg 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.[75][76]

Genetic studies

edit

WhileXenopus laevisis the most commonly used species fordevelopmental biologystudies, genetic studies, especially forward genetic studies, can be complicated by theirpseudotetraploidgenome.Xenopus tropicalisprovides a simpler model for genetic studies, having adiploidgenome.

Gene expression knockdown techniques

edit

The 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 stabilityin vivo.The chemical modifications used for this purpose include phosphorothioate, 2'-O-methyl, morpholino, MEA phosphoramidate and DEED phosphoramidate.[77]

Morpholino oligonucleotides

edit
Main article:Morpholino

Morpholino oligos are used in bothX. laevisandX. tropicalisto probe the function of a protein by observing the results of eliminating the protein's activity.[77][78]For example, a set ofX. tropicalisgenes has been screened in this fashion.[79]

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 earlyXenopusembryos 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,[78]including:

  • Phenocopy of genetic mutation
  • Verification of reduced protein by western or immunostaining
  • mRNA rescue by adding back a mRNA immune to the MO
  • use of 2 different MOs (translation blocking and splice blocking)
  • injection of control MOs

Xenbaseprovides a searchable catalog of over 2000 MOs that have been specifically used in Xenopusresearch.The data is searchable via sequence, gene symbol and various synonyms (as used in different publications).[80]Xenbase maps the MOs to the latestXenopusgenomes in GBrowse, predicts 'off-target' hits, and lists allXenopusliterature in which the morpholino has been published.

References

edit
  1. ^"Xenopus".LexicoUK English Dictionary.Oxford University Press.Archived fromthe originalon 2020-03-22.
  2. ^"Xenopus".Merriam-Webster.com Dictionary.Merriam-Webster.Retrieved2016-01-21.
  3. ^Nenni MJ, Fisher ME, James-Zorn C, Pells TJ, Ponferrada V, Chu S, et al. (2019)."Xenbase: Facilitating the Use ofXenopusto Model Human Disease ".Frontiers in Physiology.10:154.doi:10.3389/fphys.2019.00154.PMC6399412.PMID30863320.
  4. ^abcdWallingford JB, Liu KJ, Zheng Y (March 2010)."Xenopus".Current Biology.20(6):R263 –R264.Bibcode:2010CBio...20.R263W.doi:10.1016/j.cub.2010.01.012.PMID20334828.
  5. ^abcdHarland RM, Grainger RM (December 2011)."Xenopus research: metamorphosed by genetics and genomics".Trends in Genetics.27(12):507–515.doi:10.1016/j.tig.2011.08.003.PMC3601910.PMID21963197.
  6. ^abc"IACUC Learning Module —Xenopus laevis".University of Arizona. Archived fromthe originalon 2010-06-26.Retrieved2009-10-11.
  7. ^abRoots C (2006).Nocturnal animals.Greenwood Press. p. 19.ISBN978-0-313-33546-4.
  8. ^abcdePassmore NI, Carruthers VC (1979).South African Frogs.Johannesburg: Witwatersrand University Press. pp.42–43.ISBN0-85494-525-3.
  9. ^Tobias ML, Corke A, Korsh J, Yin D, Kelley DB (November 2010)."Vocal competition in male Xenopus laevis frogs".Behavioral Ecology and Sociobiology.64(11):1791–1803.doi:10.1007/s00265-010-0991-3.PMC3064475.PMID21442049.
  10. ^Tobias ML, Viswanathan SS, Kelley DB (February 1998)."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.Bibcode:1998PNAS...95.1870T.doi:10.1073/pnas.95.4.1870.PMC19205.PMID9465109.
  11. ^[Xenopus] atFossilworks.org
  12. ^Session AM, Uno Y, Kwon T, Chapman JA, Toyoda A, Takahashi S, et al. (October 2016)."Genome evolution in the allotetraploid frog Xenopus laevis".Nature.538(7625):336–343.Bibcode:2016Natur.538..336S.doi:10.1038/nature19840.PMC5313049.PMID27762356.
  13. ^Schmid M, Evans BJ, Bogart JP (2015)."Polyploidy in Amphibia".Cytogenetic and Genome Research.145(3–4):315–330.doi:10.1159/000431388.PMID26112701.
  14. ^Hogben L, Charles E, Slome D (1931)."Studies on the pituitary. 8. The relation of the pituitary gland to calcium metabolism and ovarian function in Xenopus".Journal of Experimental Biology.8:345–54.doi:10.1242/jeb.8.4.345.
  15. ^Elkan ER (December 1938)."The Xenopus Pregnancy Test".British Medical Journal.2(4067): 1253–1274.2.doi:10.1136/bmj.2.4067.1253.PMC2211252.PMID20781969.
  16. ^Diagnosis of Pregnancy,Louis P. Bosman, British Medical Journal 1937;2:939, 6 November 1937
  17. ^Nuwer R(16 May 2013)."Doctors Used to Use Live African Frogs As Pregnancy Tests".Smithsonian.com.Retrieved30 October2018.
  18. ^"The National Xenopus Resource".Marine Biological Laboratory.Retrieved2022-04-05.
  19. ^Karimi K, Fortriede JD, Lotay VS, Burns KA, Wang DZ, Fisher ME, et al. (January 2018)."Xenbase: a genomic, epigenomic and transcriptomic model organism database".Nucleic Acids Research.46(D1):D861 –D868.doi:10.1093/nar/gkx936.PMC5753396.PMID29059324.
  20. ^"Xenopus model organism database".Xenbase.org.
  21. ^Hardwick LJ, Philpott A (December 2015)."An oncologist׳s friend: How Xenopus contributes to cancer research".Developmental Biology.Modeling Human Development and Disease in Xenopus.408(2):180–187.doi:10.1016/j.ydbio.2015.02.003.PMC4684227.PMID25704511.
  22. ^Gurdon JB, Lane CD, Woodland HR, Marbaix G (September 1971). "Use of frog eggs and oocytes for the study of messenger RNA and its translation in living cells".Nature.233(5316):177–182.Bibcode:1971Natur.233..177G.doi:10.1038/233177a0.PMID4939175.S2CID4160808.
  23. ^Reynolds FH, Premkumar E, Pitha PM (December 1975)."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.Bibcode:1975PNAS...72.4881R.doi:10.1073/pnas.72.12.4881.PMC388836.PMID1061077.
  24. ^Heasman J, Kofron M, Wylie C (June 2000)."Beta-catenin signaling activity dissected in the early Xenopus embryo: a novel antisense approach".Developmental Biology.222(1):124–134.doi:10.1006/dbio.2000.9720.PMID10885751.
  25. ^Schäfer T, Pütz M, Lienkamp S, Ganner A, Bergbreiter A, Ramachandran H, et al. (December 2008)."Genetic and physical interaction between the NPHP5 and NPHP6 gene products".Human Molecular Genetics.17(23):3655–3662.doi:10.1093/hmg/ddn260.PMC2802281.PMID18723859.
  26. ^Reversade B, Escande-Beillard N, Dimopoulou A, Fischer B, Chng SC, Li Y, et al. (September 2009). "Mutations in PYCR1 cause cutis laxa with progeroid features".Nature Genetics.41(9):1016–1021.doi:10.1038/ng.413.PMID19648921.S2CID10221927.
  27. ^Pittman AM, Naranjo S, Webb E, Broderick P, Lips EH, van Wezel T, et al. (June 2009)."The colorectal cancer risk at 18q21 is caused by a novel variant altering SMAD7 expression".Genome Research.19(6):987–993.doi:10.1101/gr.092668.109.PMC2694486.PMID19395656.
  28. ^Joukov V, Groen AC, Prokhorova T, Gerson R, White E, Rodriguez A, et al. (November 2006)."The BRCA1/BARD1 heterodimer modulates ran-dependent mitotic spindle assembly".Cell.127(3):539–552.doi:10.1016/j.cell.2006.08.053.PMID17081976.S2CID17769149.
  29. ^You Z, Bailis JM, Johnson SA, Dilworth SM, Hunter T (November 2007). "Rapid activation of ATM on DNA flanking double-strand breaks".Nature Cell Biology.9(11):1311–1318.doi:10.1038/ncb1651.PMID17952060.S2CID17389213.
  30. ^abBen-Yehoyada M, Wang LC, Kozekov ID, Rizzo CJ, Gottesman ME, Gautier J (September 2009)."Checkpoint signaling from a single DNA interstrand crosslink".Molecular Cell.35(5):704–715.doi:10.1016/j.molcel.2009.08.014.PMC2756577.PMID19748363.
  31. ^Sobeck A, Stone S, Landais I, de Graaf B, Hoatlin ME (September 2009)."The Fanconi anemia protein FANCM is controlled by FANCD2 and the ATR/ATM pathways".The Journal of Biological Chemistry.284(38):25560–25568.doi:10.1074/jbc.M109.007690.PMC2757957.PMID19633289.
  32. ^Dominguez-Sola D, Ying CY, Grandori C, Ruggiero L, Chen B, Li M, et al. (July 2007). "Non-transcriptional control of DNA replication by c-Myc".Nature.448(7152):445–451.Bibcode:2007Natur.448..445D.doi:10.1038/nature05953.PMID17597761.S2CID4422771.
  33. ^Dean S, Marchetti R, Kirk K, Matthews KR (May 2009)."A surface transporter family conveys the trypanosome differentiation signal".Nature.459(7244):213–217.Bibcode:2009Natur.459..213D.doi:10.1038/nature07997.PMC2685892.PMID19444208.
  34. ^Bockenhauer D, Feather S, Stanescu HC, Bandulik S, Zdebik AA, Reichold M, et al. (May 2009)."Epilepsy, ataxia, sensorineural deafness, tubulopathy, and KCNJ10 mutations".The New England Journal of Medicine.360(19):1960–1970.doi:10.1056/NEJMoa0810276.PMC3398803.PMID19420365.
  35. ^Gustina AS, Trudeau MC (August 2009)."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.Bibcode:2009PNAS..10613082G.doi:10.1073/pnas.0900180106.PMC2722319.PMID19651618.
  36. ^Duarri A, Teijido O, López-Hernández T, Scheper GC, Barriere H, Boor I, et al. (December 2008)."Molecular pathogenesis of megalencephalic leukoencephalopathy with subcortical cysts: mutations in MLC1 cause folding defects".Human Molecular Genetics.17(23):3728–3739.doi:10.1093/hmg/ddn269.PMC2581428.PMID18757878.
  37. ^Blitz IL, Biesinger J, Xie X, Cho KW (December 2013)."Biallelic genome modification in F(0) Xenopus tropicalis embryos using the CRISPR/Cas system".Genesis.51(12):827–834.doi:10.1002/dvg.22719.PMC4039559.PMID24123579.
  38. ^Nakayama T, Fish MB, Fisher M, Oomen-Hajagos J, Thomsen GH, Grainger RM (December 2013)."Simple and efficient CRISPR/Cas9-mediated targeted mutagenesis in Xenopus tropicalis".Genesis.51(12):835–843.doi:10.1002/dvg.22720.PMC3947545.PMID24123613.
  39. ^Wang F, Shi Z, Cui Y, Guo X, Shi YB, Chen Y (2015-04-14)."Targeted gene disruption in Xenopus laevis using CRISPR/Cas9".Cell & Bioscience.5(1): 15.doi:10.1186/s13578-015-0006-1.PMC4403895.PMID25897376.
  40. ^Bhattacharya D, Marfo CA, Li D, Lane M, Khokha MK (December 2015)."CRISPR/Cas9: An inexpensive, efficient loss of function tool to screen human disease genes in Xenopus".Developmental Biology.Modeling Human Development and Disease in Xenopus.408(2):196–204.doi:10.1016/j.ydbio.2015.11.003.PMC4684459.PMID26546975.
  41. ^Dupont S, Mamidi A, Cordenonsi M, Montagner M, Zacchigna L, Adorno M, et al. (January 2009)."FAM/USP9x, a deubiquitinating enzyme essential for TGFbeta signaling, controls Smad4 monoubiquitination".Cell.136(1):123–135.doi:10.1016/j.cell.2008.10.051.PMID19135894.S2CID16458957.
  42. ^Cordenonsi M, Montagner M, Adorno M, Zacchigna L, Martello G, Mamidi A, et al. (February 2007)."Integration of TGF-beta and Ras/MAPK signaling through p53 phosphorylation".Science.315(5813):840–843.Bibcode:2007Sci...315..840C.doi:10.1126/science.1135961.PMID17234915.S2CID83962686.
  43. ^Fuentealba LC, Eivers E, Ikeda A, Hurtado C, Kuroda H, Pera EM, De Robertis EM (November 2007)."Integrating patterning signals: Wnt/GSK3 regulates the duration of the BMP/Smad1 signal".Cell.131(5):980–993.doi:10.1016/j.cell.2007.09.027.PMC2200633.PMID18045539.
  44. ^Kim NG, Xu C, Gumbiner BM (March 2009)."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.Bibcode:2009PNAS..106.5165K.doi:10.1073/pnas.0810185106.PMC2663984.PMID19289839.
  45. ^Kaláb P, Pralle A, Isacoff EY, Heald R, Weis K (March 2006). "Analysis of a RanGTP-regulated gradient in mitotic somatic cells".Nature.440(7084):697–701.Bibcode:2006Natur.440..697K.doi:10.1038/nature04589.PMID16572176.S2CID4398374.
  46. ^Tsai MY, Wang S, Heidinger JM, Shumaker DK, Adam SA, Goldman RD, Zheng Y (March 2006). "A mitotic lamin B matrix induced by RanGTP required for spindle assembly".Science.311(5769):1887–1893.Bibcode:2006Sci...311.1887T.doi:10.1126/science.1122771.PMID16543417.S2CID12219529.
  47. ^Ma L, Tsai MY, Wang S, Lu B, Chen R, Yates JR, et al. (March 2009)."Requirement for Nudel and dynein for assembly of the lamin B spindle matrix".Nature Cell Biology.11(3):247–256.doi:10.1038/ncb1832.PMC2699591.PMID19198602.
  48. ^Emanuele MJ, Stukenberg PT (September 2007)."Xenopus Cep57 is a novel kinetochore component involved in microtubule attachment".Cell.130(5):893–905.doi:10.1016/j.cell.2007.07.023.PMID17803911.S2CID17520550.
  49. ^abNoireaux V, Liu AP (June 2020)."The New Age of Cell-Free Biology".Annual Review of Biomedical Engineering.22(1).Annual Reviews:51–77.doi:10.1146/annurev-bioeng-092019-111110.PMID32151150.S2CID212652742.
  50. ^Akkers RC, van Heeringen SJ, Jacobi UG, Janssen-Megens EM, Françoijs KJ, Stunnenberg HG, Veenstra GJ (September 2009)."A hierarchy of H3K4me3 and H3K27me3 acquisition in spatial gene regulation in Xenopus embryos".Developmental Cell.17(3):425–434.doi:10.1016/j.devcel.2009.08.005.PMC2746918.PMID19758566.
  51. ^Hontelez S, van Kruijsbergen I, Georgiou G, van Heeringen SJ, Bogdanovic O, Lister R, Veenstra GJ (December 2015)."Embryonic transcription is controlled by maternally defined chromatin state".Nature Communications.6:10148.Bibcode:2015NatCo...610148H.doi:10.1038/ncomms10148.PMC4703837.PMID26679111.
  52. ^Walker JC, Harland RM (May 2009)."microRNA-24a is required to repress apoptosis in the developing neural retina".Genes & Development.23(9):1046–1051.doi:10.1101/gad.1777709.PMC2682950.PMID19372388.
  53. ^Rosa A, Spagnoli FM, Brivanlou AH (April 2009)."The miR-430/427/302 family controls mesendodermal fate specification via species-specific target selection".Developmental Cell.16(4):517–527.doi:10.1016/j.devcel.2009.02.007.PMID19386261.
  54. ^Park JI, Venteicher AS, Hong JY, Choi J, Jun S, Shkreli M, et al. (July 2009)."Telomerase modulates Wnt signalling by association with target gene chromatin".Nature.460(7251):66–72.Bibcode:2009Natur.460...66P.doi:10.1038/nature08137.PMC4349391.PMID19571879.
  55. ^De Val S, Chi NC, Meadows SM, Minovitsky S, Anderson JP, Harris IS, et al. (December 2008)."Combinatorial regulation of endothelial gene expression by ets and forkhead transcription factors".Cell.135(6):1053–1064.doi:10.1016/j.cell.2008.10.049.PMC2782666.PMID19070576.
  56. ^Li Y, Rankin SA, Sinner D, Kenny AP, Krieg PA, Zorn AM (November 2008)."Sfrp5 coordinates foregut specification and morphogenesis by antagonizing both canonical and noncanonical Wnt11 signaling".Genes & Development.22(21):3050–3063.doi:10.1101/gad.1687308.PMC2577796.PMID18981481.
  57. ^Carmona-Fontaine C, Matthews HK, Kuriyama S, Moreno M, Dunn GA, Parsons M, et al. (December 2008)."Contact inhibition of locomotion in vivo controls neural crest directional migration".Nature.456(7224):957–961.Bibcode:2008Natur.456..957C.doi:10.1038/nature07441.PMC2635562.PMID19078960.
  58. ^Buitrago-Delgado E, Nordin K, Rao A, Geary L, LaBonne C (June 2015)."NEURODEVELOPMENT. Shared regulatory programs suggest retention of blastula-stage potential in neural crest cells".Science.348(6241):1332–1335.doi:10.1126/science.aaa3655.PMC4652794.PMID25931449.
  59. ^Gaiano N, Fishell G (2002). "The role of notch in promoting glial and neural stem cell fates".Annual Review of Neuroscience.25(1).Annual Reviews:471–490.doi:10.1146/annurev.neuro.25.030702.130823.PMID12052917.S2CID15691580.
  60. ^Tsuji T, Lau E, Chiang GG, Jiang W (December 2008)."The role of Dbf4/Drf1-dependent kinase Cdc7 in DNA-damage checkpoint control".Molecular Cell.32(6):862–869.doi:10.1016/j.molcel.2008.12.005.PMC4556649.PMID19111665.
  61. ^Xu X, Rochette PJ, Feyissa EA, Su TV, Liu Y (October 2009)."MCM10 mediates RECQ4 association with MCM2-7 helicase complex during DNA replication".The EMBO Journal.28(19):3005–3014.doi:10.1038/emboj.2009.235.PMC2760112.PMID19696745.
  62. ^Räschle M, Knipscheer P, Knipsheer P, Enoiu M, Angelov T, Sun J, et al. (September 2008)."Mechanism of replication-coupled DNA interstrand crosslink repair".Cell.134(6):969–980.doi:10.1016/j.cell.2008.08.030.PMC2748255.PMID18805090.
  63. ^MacDougall CA, Byun TS, Van C, Yee MC, Cimprich KA (April 2007)."The structural determinants of checkpoint activation".Genes & Development.21(8):898–903.doi:10.1101/gad.1522607.PMC1847708.PMID17437996.
  64. ^Nutt LK, Buchakjian MR, Gan E, Darbandi R, Yoon SY, Wu JQ, et al. (June 2009)."Metabolic control of oocyte apoptosis mediated by 14-3-3zeta-regulated dephosphorylation of caspase-2".Developmental Cell.16(6):856–866.doi:10.1016/j.devcel.2009.04.005.PMC2698816.PMID19531356.
  65. ^Viczian AS, Solessio EC, Lyou Y, Zuber ME (August 2009)."Generation of functional eyes from pluripotent cells".PLOS Biology.7(8): e1000174.doi:10.1371/journal.pbio.1000174.PMC2716519.PMID19688031.
  66. ^Dzamba BJ, Jakab KR, Marsden M, Schwartz MA, DeSimone DW (March 2009)."Cadherin adhesion, tissue tension, and noncanonical Wnt signaling regulate fibronectin matrix organization".Developmental Cell.16(3):421–432.doi:10.1016/j.devcel.2009.01.008.PMC2682918.PMID19289087.
  67. ^Beattie MS, Bresnahan JC, Lopate G (October 1990). "Metamorphosis alters the response to spinal cord transection in Xenopus laevis frogs".Journal of Neurobiology.21(7):1108–1122.doi:10.1002/neu.480210714.PMID2258724.
  68. ^Park TJ, Mitchell BJ, Abitua PB, Kintner C, Wallingford JB (July 2008)."Dishevelled controls apical docking and planar polarization of basal bodies in ciliated epithelial cells".Nature Genetics.40(7):871–879.doi:10.1038/ng.104.PMC2771675.PMID18552847.
  69. ^Mitchell B, Jacobs R, Li J, Chien S, Kintner C (May 2007). "A positive feedback mechanism governs the polarity and motion of motile cilia".Nature.447(7140):97–101.Bibcode:2007Natur.447...97M.doi:10.1038/nature05771.PMID17450123.S2CID4415593.
  70. ^Kälin RE, Bänziger-Tobler NE, Detmar M, Brändli AW (July 2009)."An in vivo chemical library screen in Xenopus tadpoles reveals novel pathways involved in angiogenesis and lymphangiogenesis".Blood.114(5):1110–1122.doi:10.1182/blood-2009-03-211771.PMC2721788.PMID19478043.
  71. ^Ny A, Koch M, Vandevelde W, Schneider M, Fischer C, Diez-Juan A, et al. (September 2008)."Role of VEGF-D and VEGFR-3 in developmental lymphangiogenesis, a chemicogenetic study in Xenopus tadpoles".Blood.112(5):1740–1749.doi:10.1182/blood-2007-08-106302.PMID18474726.S2CID14663578.
  72. ^Cha HJ, Byrom M, Mead PE, Ellington AD, Wallingford JB, Marcotte EM (2012-01-01)."Evolutionarily repurposed networks reveal the well-known antifungal drug thiabendazole to be a novel vascular disrupting agent".PLOS Biology.10(8): e1001379.doi:10.1371/journal.pbio.1001379.PMC3423972.PMID22927795.
  73. ^Zimmer C (2012-08-21)."Gene Tests in Yeast Aid Work on Cancer".The New York Times.
  74. ^Fini JB, Le Mevel S, Turque N, Palmier K, Zalko D, Cravedi JP, Demeneix BA (August 2007). "An in vivo multiwell-based fluorescent screen for monitoring vertebrate thyroid hormone disruption".Environmental Science & Technology.41(16):5908–5914.Bibcode:2007EnST...41.5908F.doi:10.1021/es0704129.PMID17874805.
  75. ^Dupré A, Boyer-Chatenet L, Sattler RM, Modi AP, Lee JH, Nicolette ML, Kopelovich L, Jasin M, Baer R, Paull TT, Gautier J (February 2008)."A forward chemical genetic screen reveals an inhibitor of the Mre11-Rad50-Nbs1 complex".Nature Chemical Biology.4(2):119–25.doi:10.1038/nchembio.63.PMC3065498.PMID18176557.
  76. ^Landais I, Sobeck A, Stone S, LaChapelle A, Hoatlin ME (February 2009)."A novel cell-free screen identifies a potent inhibitor of the Fanconi anemia pathway".International Journal of Cancer.124(4):783–92.doi:10.1002/ijc.24039.PMID19048618.S2CID33589304.
  77. ^abDagle JM, Weeks DL (December 2001). "Oligonucleotide-based strategies to reduce gene expression".Differentiation; Research in Biological Diversity.69(2–3):75–82.doi:10.1046/j.1432-0436.2001.690201.x.PMID11798068.
  78. ^abBlum M, De Robertis EM, Wallingford JB, Niehrs C (October 2015)."Morpholinos: Antisense and Sensibility".Developmental Cell.35(2):145–149.doi:10.1016/j.devcel.2015.09.017.PMID26506304.
  79. ^Rana AA, Collart C, Gilchrist MJ, Smith JC (November 2006)."Defining synphenotype groups in Xenopus tropicalis by use of antisense morpholino oligonucleotides".PLOS Genetics.2(11): e193.doi:10.1371/journal.pgen.0020193.PMC1636699.PMID17112317.
    "AXenopus tropicalisantisense morpholino screen ".Gurdon Institute. 4 March 2014. Archived fromthe originalon 12 June 2018.Retrieved17 January2007.
  80. ^Xenbase
edit
  • Xenbase~ AXenopus laevisandtropicalisWeb Resource
Retrieved from "https://en.wikipedia.org/w/index.php?title=Xenopus&oldid=1238092882"