Talk:Frog Development

Background Reading

PLoS Biology

• Neural Induction in Xenopus: Requirement for Ectodermal and Endomesodermal Signals via Chordin, Noggin, β-Catenin, and Cerberus
• Controlling the Timing of Gene Expression during Organ Development
• Organizing the Vertebrate Embryo—A Balance of Induction and Competence

• Genetic Screens for Mutations Affecting Development of Xenopus tropicalis Tadahiro Goda, Anita Abu-Daya, Samantha Carruthers, Matthew D Clark, Derek L Stemple, and Lyle B Zimmerman PLoS Genet. 2006 June; 2(6): e91. Prepublished online 2006 April 28. Published online 2006 June 9. doi: 10.1371/journal.pgen.0020091. PMCID: PMC1475704

Frog Mitochondrial Genome

The complete nucleotide sequence of the Xenopus laevis mitochondrial genome. "The complete sequence of the 17,553-nucleotide Xenopus laevis mitochondrial genome has been determined. A comparison of this amphibian mitochondrial genomic sequence with those of the mammalian mitochondrial genomes reveals a similar gene order and compact genomic organization."

Xenopus laevis mitochondrial DNA, complete genome - 17553 bp GenBank report

Introduction

There are several different species of frog that have been used in many developmental studies. The frog was historically used by many of the early embryology investigators and currently there are many different molecular mechanisms concerning development of the frog.

File:Xenopus.gif Xenopus

The frog Xenopus laevis (African clawed frog, [#Taxon taxon]) has been used in many embryological and electrophysiological studies (More? see [frog4.htm Cell lineages]). The advantages of this frog is the fertility cycle can be easliy controlled and the eggs develop entirely independently and easily visible to the investigator. You can see an overview of the [frog1.htm#Frog%20Life%20Cycle Frog life cycle] with links to specific stages as well as movies of the early [frog2.htm process of gastrulation]. Localization of maternal messenger RNA (eg [#melton1 vegetal] and [#Mowry review]) appears to play a key role in the development of early embryological patterns.

The frog species Rana pipiens (Leopard frog) in 1952 became the first successful nuclear transfer experiment. Nuclear transfer is an embryological technique, and involves removal of the nucleus from an egg and replacement with the nucleus of another donor cell. This experiment paved the way for what we know today as the field of cloning. (More? read recent PNAS Article Nuclear Transfer: Bringing in the Clones | Original 1952 Paper Briggs, R. & King, T. J. (1952) Proc. Natl. Acad. Sci. USA 38, 455-463.)

In Australia Bufo marinus (cane toad) was a species introduced in 1935 to control cane insect pests. It has itself become an introduced pest and has also been studied/used more in order to try and biologically control. The area which they occupy has continued to expand. The toad has a poisonous secretion that is extremely toxic and should be handled with care at all times.

Page Links: [#Intro Introduction] | [#Recent Some Recent Findings] | [#Taxon Taxon] | [#External WWW External WWW] | [#References References]

Other Pages: [frog1.htm#Frog%20Life%20Cycle Frog life cycle] | [frog2.htm Frog Gastrulation] | [frog3.htm Frog localized mRNAs] | [../Movies/MRI.htm Frog Blastula MRI]

Some Recent Findings

Heart Development Yoshimoto S, Okada E, Umemoto H, Tamura K, Uno Y, Nishida-Umehara C, Matsuda Y, Takamatsu N, Shiba T, Ito M. A W-linked DM-domain gene, DM-W, participates in primary ovary development in Xenopus laevis. Proc Natl Acad Sci U S A. 2008 Feb 11;

"In the XX/XY sex-determining system, the Y-linked SRY genes of most mammals and the DMY/Dmrt1bY genes of the teleost fish medaka have been characterized as sex-determining genes that trigger formation of the testis. However, the molecular mechanism of the ZZ/ZW-type system in vertebrates, including the clawed frog Xenopus laevis, is unknown. ...these results suggest that DM-W is a likely sex (ovary)-determining gene in X. laevis."

(More? [../Notes/genitalXX.htm Genital System - Female])

Taxon

Xenopus Laevis

• Eukaryotae; mitochondrial eukaryotes; Metazoa; Chordata;Vertebrata; Amphibia; Batrachia; Anura; Mesobatrachia; Pipoidea;Pipidae; Xenopodinae; Xenopus

Rana pipiens

Taxonomy Id: 8404 Preferred common name: northern leopard frog Rank: species

Genetic code: Translation table 1 (Standard) Mitochondrial genetic code: Translation table 2 Lineage( abbreviated ):

• Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Amphibia; Batrachia; Anura; Neobatrachia; Ranoidea; Ranidae; Raninae; Rana

External WWW Links

Note the dynamic developmental nature of the Internet means that some links may not always work (search using the link term).

• Xenbase A database of information pertaining to the cell and developmental biology of the frog, Xenopus
• Xenopus Laboratory List A database of Labs studying Xenopus
• Xenopus Microarrays
• Xenopus Cell Biology
• The Xenopus Molecular Marker Resource
  • An electronic library of information on embryonic development of the frog, Xenopus laevis.
    • Excellent site designed and Managed by Peter D. Vize, UT Austin.
  • Index page for all Markers
  • It also contains a collection of wholemount staining patterns
  • Molecular Markers of Development
    • cement gland; XA, XAG, XCG
    • early mesoderm; BMP2, BMP4, Chordin, goosecoid, Mix,[Marker_pages/organizer/noggin.html noggin], Xbra, Xnr3, Xwnt-8, XVent1 and XVent2
    • endothelial; Xl-fli
    • germ cells; Xpat
    • heart; cardiac troponin I , XNKX-2.5, XTin1 (XNKX-2.3)
    • lateral line; tor70, [Marker_pages/CNS/2G9.html 2G9]
    • muscle; 5A3, 12/101, cardiac actin, XMyf-5, XMyoD
    • neural crest; Slug, XTwist , xAP2
    • notochord: Xnot, tor70
    • pronephros; [Marker_pages/pronephros/3G8.html 3G8 ], Wilms' tumor (xWT1), Xlim-1, Xwnt-4
    • pronephric duct; 4A6
    • Frogs of Greater Brisbane Region (Australia)
• DNA SequenceXenopus laevis mitochondrial DNA, complete genome- 17553 bp
  • gi|343717|gb|M10217.1|XELMTCG [343717] View GenBank report
  • The complete nucleotide sequence of the Xenopus laevis mitochondrial genome. Roe,B.A., Ma,D.P., Wilson,R.K. and Wong,J.F. J. Biol. Chem. 260 (17), 9759-9774 (1985)
    • Abstract: The complete sequence of the 17,553-nucleotide Xenopus laevis mitochondrial genome has been determined. A comparison of this amphibian mitochondrial genomic sequence with those of the mammalian mitochondrial genomes reveals a similar gene order and compact genomic organization.
• Developmental Biology- Laurie Iten's Serially Sectioned Frog and Chick Embryos
• Developmental Biology- Jeff Hardin's Amphibian Embryology Tutorial
• NIH- Organisms for biomedical research

References

PubMed

Requires internet connection.

Search PubMed:term=frog+development | term=xenopus+development

Developmental Biology (6th ed) Gilbert: Frog Life Cycle

Molecular Cell Biology (4th ed.)Lodish Figure 23-5. Early embryogenesis of the frog Xenopus laevis

• Organisation of Xenopus oocyte and egg cortices. Chang P, Perez-Mongiovi D, Houliston E Microsc Res Tech 1999 Mar 15;44(6):415-29
  • Abstract: The division of the Xenopus oocyte cortex into structurally and functionally distinct "animal" and "vegetal" regions during oogenesis provides the basis of the organisation of the early embryo. The vegetal region of the cortex accummulates specific maternal mRNAs that specify the development of the endoderm and mesoderm, as well as functionally-defined "determinants" of dorso-anterior development, and recognisable "germ plasm" determinants that segregate into primary germ cells. These localised elements on the vegetal cortex underlie both the primary animal-vegetal polarity of the egg and the organisation of the developing embryo. The animal cortex meanwhile becomes specialised for the events associated with fertilisation: sperm entry, calcium release into the cytoplasm, cortical granule exocytosis, and polarised cortical contraction. Cortical and subcortical reorganisations associated with meiotic maturation, fertilisation, cortical rotation, and the first mitotic cleavage divisions redistribute the vegetal cortical determinants, contributing to the specification of dorso-anterior axis and segregation of the germ line. In this article we consider what is known about the changing organisation of the oocyte and egg cortex in relation to the mechanisms of determinant localisation, anchorage, and redistribution, and show novel ultrastructural views of cortices isolated at different stages and processed by the rapid-freeze deep-etch method. Cortical organisation involves interactions between the different cytoskeletal filament systems and internal membranes. Associated proteins and cytoplasmic signals probably modulate these interactions in stage-specific ways, leaving much to be understood.
• Translocation of a localized maternal mRNA to the vegetal pole of Xenopus oocytes. Melton DA Nature 1987 Jul 2-8;328(6125):80-2
  • A key paper in establishing localization of maternal mRNAs as regulators of developmental pattern formation. This localization of mRNAs has also been found for many different drosophila (fly) mRNAs with many different patterns.
  • Abstract: A prominent hypothesis in embryology is that localized maternal factors are important in specifying cell fate. There are, however, only a few examples of maternal molecules that have been shown to be localized and very little is known about how such factors are physically localized within an egg (for review see ref. 1). Previously, cDNA clones were obtained for a class of localized maternal mRNAs from Xenopus laevis. These mRNAs are unusual in that they are concentrated at either the animal or vegetal pole of unfertilized eggs. In the present study the synthesis and intracellular distribution of one of them, Vg1, has been examined during oogenesis. The results show that Vg1 mRNA is localized as a crescent at the vegetal pole of mature oocytes. Surprisingly, this mRNA is uniformly distributed in the cytoplasm of immature oocytes. These findings suggest that a single cell, the frog oocyte, has some mechanism for translocating specific RNAs like Vg1. The process that moves Vg1 mRNA is evidently a cytoplasmic localization machinery which is not directly coupled to the synthesis of Vg1 RNA.
• A two-step model for the localization of maternal mRNA in Xenopus oocytes: involvement of microtubules and microfilaments in the translocation and anchoring of Vg1 mRNA. Yisraeli JK, Sokol S, Melton DA Development 1990 Feb;108(2):289-98.
  • Abstract: In an effort to understand how polarity is established in Xenopus oocytes, we have analyzed the process of localization of the maternal mRNA, Vg1. In fully grown oocytes, Vg1 mRNA is tightly localized at the vegetal cortex. Biochemical fractionation shows that the mRNA is preferentially associated with a detergent-insoluble subcellular fraction. The use of cytoskeletal inhibitors suggests that (1) microtubules are involved in the translocation of the message to the vegetal hemisphere and (2) microfilaments are important for the anchoring of the message at the cortex. Furthermore, immunohistochemistry reveals that a cytoplasmic microtubule array exists during translocation. These results suggest a role for the cytoskeleton in localizing information in the oocyte.
  • RNA sorting in Xenopus oocytes and embryos. Mowry KL, Cote CA FASEB J 1999 Mar;13(3):435-45
  • mRNA localisation during development. Micklem DR Dev Biol 1995 Dec;172(2):377-95.
• Thyroid hormone-dependent metamorphosis in a direct developing frog. Callery, EM and Elinson RP, Proc. Natl. Acad. Sci. USA, Vol. 97, Issue 6, 2615-2620, March 14, 2000
  • The direct developing anuran, Eleutherodactylus coqui, lacks a tadpole, hatching as a tiny frog. We investigated the role of the metamorphic trigger, thyroid hormone (TH), in this unusual ontogeny. Expression patterns of the thyroid hormone receptors, TR and TR, were similar to those of indirect developers. TR mRNA levels increased dramatically around the time of thyroid maturation, when remodeling events reminiscent of metamorphosis occur. Treatment with the goitrogen methimazole inhibited this remodeling, which was reinitiated on cotreatment with TH. Despite their radically altered ontogeny, direct developers still undergo a TH-dependent metamorphosis, which occurs before hatching. We propose a new model for the evolution of anuran direct development.