Xenopus laevis

Jake Nieb Developmental Biology

April 15, 2014

Background and History •  African clawed frog •  “Xeno” – strange; “pus” – foot •  “laevis” – smooth •  1930s – first brought to the

United States and used as a low-cost pregnancy test [6]

–  Lancelot Hogben (comparative endocrinologist)

–  Urine injected into female hind leg, chorionic gonadotropin causes Xenopus to lay eggs [3]

•  Pieter D. Nieuwkoop – used series of experiments to show benefits of Xenopus as a model organism [3]

Classification and Genetic Information

                             

•  Vertebrate

•  Deuterostome (“mouth second”)

•  Life cycle: approximately 12 months [6]

•  Brood size: 300-1000 eggs [6]

•  Genome: 3.1 × 109 bp; 18 chromosomes; allotetraploid (four sets of chromosomes) [6]

–  Genome is structurally similar to humans

Related Species and Habitat

•  Closely related to Xenopus tropicalis[2]

•  Sub-Saharan Africa[4]

•  Aquatic [6]

Advantages •  Eggs

–  Large and Robust –  Ability to induce regardless of season

(chorionic gonadotropin) [3]

•  Fertilization –  External, easy to visualize and

manipulate [4]

•  Embryos –  Respond well to surgical procedures [5]

Advantages •  Responds well to gain-of-

function experiments[4]

•  Interactive fate maps available at xenbase (less detailed) [6]

•  Fate map from 32-cell stage published in 1987 [1]

•  Genome is sequenced [6]

•  Effective technical approaches: –  Morpholinos, RNAi,

transgenic chimeras [4]

–  Nuclear transplants and cloning [2]

Disadvantages •  Tetraploidy

–  Loss of function mutations are difficult to implement [2]

•  Comparison to X. tropicalis –  Diploid, much more

useful for loss-of-function mutations [2]

–  Shorter life cycle [6]

–  Larger brood size [6]

•  Only somewhat related to humans, less pertinent than mammalian model organisms [2]

Fun Facts •  First cloned vertebrate

(1958) – genomic equivalence [2]

•  Males lack vocal cords – mating “call” is actually muscle contractions –  Acceptance call or

Rejection call [7]

•  Populations in California, Virginia, and Delaware are overtaking native wildlife [7]

•  They were originally injected with women’s urine! [3]

References •  [1] Dale, L; Slack, J. 1987. Fate map for the 32-cell stage of Xenopus laevis. Development.

99:527-551.

•  [2] Grainger, R. 2012. Xenopus tropicalis as a model organism for genetics and genomics: past, present and future. Methods in Molecular Biology. 917:3-15.

•  [3] Gurdon, J; Hopwood, N. 2000. The introduction of Xenopus laevis into developmental biology: of empire, pregnancy testing and ribosomal genes. Journal of Developmental Biology. 44:43-50.

•  [4] Harland, R; Grainger, R. 2011. Xenopus research: metamorphosed by genetics and genomics. Trends in Genetics. 27(12):507-515.

•  [5] Hellsten, U; Harland, R; Gilchrist, M; Hendrix, D; Jurka, J; Kapitonov, V; Ovcharenko, I; Putnam, N; Shu, S; Taher, L; Blitz, I; Blumberg, B; Dichmann, D; Dubchak, I; Amaya, E; Detter, J; Fletcher, R; Gerhard, D; Goodstein, D; Graves, T; Grigoriev, I; Grimwood, J; Kawashima, T; Lindquist, E; Lucas, S; Mead, P; Mitros, T; Ogino, H; Ohta, Y; Poliakov, A; Pollet, N; Robert, J; Salamov, A; Sater, A; Schmutz, J; Terry, A; Vize, P; Warren, W; Wells, D; Wills, A; Wilson, R; Zimmerman, L; Zorn, A; Grainger, R; Grammer, T; Khokha, M; Richardson, P; Rokhsar, D. 2010. The genome of the western clawed frog Xenopus tropicalis. Science. 328:633-636.

•  [6] Xenbase. 2014. National Institute of Child Health and Human Development.

•  [7] Xenopus laevis – the African Clawed Frog. 2014. Smithsonian National Zoological Park.