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.
Xenopus
The frog Xenopus laevis (African
clawed frog, taxon)
has been used in many embryological and
electrophysiological studies
(More? see 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 Frog
life cycle with links to specific
stages as well as movies of the early
process of
gastrulation. Localization of maternal
messenger RNA (eg vegetal
and 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: Introduction | Some Recent Findings | Taxon | External WWW |
References
Other Pages: Frog life cycle | Frog Gastrulation | Frog localized mRNAs
| 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? 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.
- 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,
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,
2G9
- muscle; 5A3,
12/101,
cardiac
actin, XMyf-5,
XMyoD
- neural crest; Slug,
XTwist
, xAP2
- notochord: Xnot,
tor70
- pronephros; 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.
Comments
Note - You will be automatically sent to the current Frog Development page in 5 seconds.
This page introduces the Frog as a developmental model organism.
Frogs are readily available, the process of embryonic development easily viewed and manipulated, which made this animal a
model of choice for early embryological research. In fact historically, nuclear transfer in the frog opened the field of
cloning we know today.
Even today the entire process can be easily observed in the classroom using basically a small aquarium tank and eggs from a pond.
Please email Dr Mark Hill if you wish to make a comment about this current project.
