2009 Group Project 4: Difference between revisions

Revision as of 14:35, 29 August 2009

MOUSE

Timeline of Development

Development of the Mouse Embryo
Day 0 One Cell Egg
Day 1 Dividing Egg. Cleavage of cells has begun. The Day ends with 4 cells present.
Day 2 Morula
Day 3 Advanced segmentation of the Morula. 16-25 cells within same sized morula.
Day 4 Blastocyst formation
Day 4.5 Implantation and Invasion of the blastocyst into the uterine epithelium
Day 5 Formation of the egg cylinder
Day 6 Differentiation of the egg cylinder
Day 6.5 Gastrulation starts during the period of Advanced Endometrial Reaction
Day 7 Amnion formation
Day 7.5 Neural plate and presomite stage
Day 8 Formation of the first seven somites.
Day 8.5 Rotation of the embryo. The embryo now has between 8 and 12 somites.
Day 9 Formation and closure of the anterior neuropore. There are 13 - 20 somites present in the embryo
Day 9.5 Formation of the posterior neuropore and forelimb bud. There are 21 to 29 somites present and the embryo measures 1.8 - 3.3 mm in length.
Day 10 The posterior neuropore closes and formation of the hind limb bud and tail bud occurs. there are 30 - 34 somites present and the embryo is 3.1 - 3.9mm
Day 10.5 Deep eye lens indentation occurs. There are 35-30 somites present and the embryo is now 3.5-4.9mm.
Day 11 Closure of the lens vesicle. There are 40-44 somites present and the embryo has reached 5-6mm in length.
Day 11.5 The lens vesicle is completely separated from the surface epithelium. There are currently 45 - 47 somites and the embryo reaches a length of 6 - 7mm
Day 12 First signs of fingers. The embryo is 7 - 9mm in length from crown to rump and there are 48 - 51 somites.
Day 13 The anterior footplate becomes indented and the external ear structure is more defined. The embryo is now 9 - 11mm in length and has 52 - 55 somites.
Day 14 The fingers separate. The embryo has 56 - 66 somites and is 11-12mm in length.
Day 15 The toes separate. At this stage the embryo is 12 - 14.4m from crown to rump
Day 16 The umbilical hernia is repositioned. The fetus now measures between 14 and 17 mm.
Day 17 The fingers and toes become joined together. The skin is wrinkled and thickened and the umbilical hernia has disappeared. The fetus measures 16.5 - 20mm depending on the degree of curvature.
Day 18 Whiskers elongate. The length of the embryo varies between 18 and 23 mm due to the degree of curvature of the fetus.
Day 19 The newborn mouse is between 23 and 27mm depending on the degree of flexure of the body axis

Staging

Mouse embryonic development commences once the female's egg or oocyte has become fertilized by the male's sperm. Mouse development has a gestation period of 19-21 days, and can range in different strains of mice. The development of an embryo can be categorized into different stages including cell number, somite stages and morphology. Link to movie showing mouse embryo [1] The most common method of staging is by Theiler (1989) which categorizes mouse development into prenatal and postnatal stages consisting of 26 and 2 stages respectively. Downs and Davies (1993 ) have also established a method of staging the mouse development based on morphological changes. Link to Downs and Davies [2]

Picture 1: Photo of a one day old mouse Wikipedia 2009

Figure 1: Illustration of Mouse embryonic stages of development from fertilization to zona free blastocyst (stages 1 to 5). E.Newton 2009

Figure 2: Illustration of Theiler stage 8 (6 dpc). E.Newton 2009

Figure 3: Illustration of Theiler stage 10 (7 dpc). E.Newton 2009

Figure 4: Illustration of Theiler stage 11. E.Newton 2009

Table 1: Mouse embryonic stages of development from fertilization to zona free blastocyst (Stages 1 to 5)
Theiler Stage	Embryonic Age in Days Post Coitum (dpc)	Stage Characteristic	Cell Characteristics	Zona Pellucida	Location
1	0-0.9 (range 0-0.25)	One-celled embryo (fertilized)	One cell	Present	Ampulla
2	1 (range 1-2.5)	Dividing egg	2-4 cells - 1st cleavage after 24hrs	Present	Travelling down oviduct
3	2 (range 1-3.5)	Morula (early to fully compacted)	4-16 cells	Present	Oviduct. Usually near utero-tubal junction.
4	3 (range 2-4)	Change from Morula to Blastocyst -Intra-cellular matrix present -Blastocoelic cavity evident	16-40 compacted cells -Inner cell mass -Outer layer of trophectoderm cells	Present	Uterine lumen
5	4 (range 3-5.5)	Zona free Blastocyst (hatching)	Blastocyst is ready to implant as surrounding cell layer of zona pelludica is lost	Absent	Uterine lumen

Dr Mark Hill 2009, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G

Link to ultrasound of mouse embryo [3]

Table 2: Mouse embryonic staging from blastocyst implantation to pre-somite formation (stage 6 to 11c)
Theiler Stage	Embryonic age in Days Post Coitum (dpc)	Stage Characteristic	Cell characteristics
6	4.5 (range 4-5.5) Human carnegie stage: 4	Attachment of blastocyst -Implantation	Embryonic Endoderm present covering the blastocoelic cells of the inner cell mass.
7	5 (range 4.5-6) Human carnegie stage: 5	Implantation -Egg cylinder formation -Ectoplacental cone	Inner cell mass increases in size -Epiblast formation (enlarged mass) -Proximal cells are cuboidal in shape -Mural trophectoderm is lined by primary endoderm
8	6 (range 5-6.5) Human carnegie stage: 5	Differentiation of egg cylinder into embryonic and extra-embryonic regions -Pro-amniotic cavity formation	Trophoblast giant cells invade maternal tissue -Maternal blood invades the ectoplacental cone -Reichert's membrane appears -Implantation site is 2x3mm
9 a)	Pre-streak	Advanced Endometrial and egg cylinder stage -First evidence of embryonic axis	Morphological difference can be seen between embryonic and extra-embryonic ectoderm -Maternal blood further invades ectoplacental cone -Uterine crypts lose their original lumen
9 b)	Early streak	Gastrulation begins (later in stage)	First mesodermal cells produced
10 a)	7 (range 6.5-7.5) Mid streak to late streak Human carnegie stage: 8	Amnion formation	The amniotic fold starts to form from posterior tissue of primitive streak bulging. -Allantoic bud evident -Gastrulation continues -Primitive node visible -Amnion begins to close
11	7.5 (range 7.25-8) Human carnegie stage: 9	Formation of neural plate and presomites	Amniotic cavity is sealed to form 3 cavities (amniotic cavity, exocoelom and ectoplacental cleft) -Allantoic bud elongates -Notochodal plate can be seen in the midline and subjacent to neural groove -Head form from the enlargement of the rostral end of neural plate (early head fold) -Formation of foregut pocket begins

History of Model Use

Introduction

The mouse has contributed an important part of research and finings in the biomedical field since the middle of the sixteenth century (Hendrich et al. 2004). This research using the mouse, especially the mouse embryo, has continued into and multiplied in the 20th century.

It's popularity over time in mammalian biology, biomedicine, immunology, oncology, pathology, and genetics is a result of:

The mouse breeding system: consistently monitoring the characterisitcs, that are precisley known, generation after generation, thereby producing highly standardised strains (Hedrich et al. 2004).

The metabolic and internal anatomical similarities between the mouse and the human allowing for comparisons. Because of these similarities, they share similar diseases, for example, cancer, diabetes, autoimmunity, endocrine disease, and neurological dysfunctions (Hedrich et al. 2004).

1895: Dr. Johannes Sobotta

Researched the fertilisation and cleavage of the mouse's egg (Sobotta, 1895). Link to Dr. Sobotta's research [4]

What did he find?

The corpus Luteum is formed by the enlargement of the epithelial cells of the follicle, aided by growth of connective tissue.
There is no distinction between corpora lutea vera and corpora lutea spuria.
The corpora lutea do not degenerate. They remain unchanged during the life of the animal, and therefore add to the size of the ovary.

1958: Professor Dame Anne McLaren

Developed the first birth of mice in-vitro. Link to Published article [5]

1962: George Todaro and Howard Green

By studying the fibroblast cells of the mouse embryo , they explained how cells behave in a similar fashion once they have undergone transformation (Bhamrah et al. 2002).

How did they do this?

Todaro and Green cultured the fibroblast cells from the mouse embryo.

What did they find?

A few weeks after the culture, the growth rate of the Fibroblast cells slowed down. They thought that the cells, as with normal human fibroblast cells, would eventually stop didviding and die. However this was not the case.

Two to three months later, the cell growth rate increased. This meant that the resulting new population of cells had undergone spontaneous transformation. The resulting permanently dividing cell line, called the '3T3 cell line', have been growing in culture for over 20 years. (Bhamrah et al. 2002)

Genetics

Genome

Sequencing of the mouse genome was completed in late 2002. Tha haploid genome is about 3 billion long (3000 Mb distributed over 20 chromosomes) and therefore equal to the size of the human genome. The current estimated gene count is 23,786 and humans are estimated to have 23,686 genes.

The genetic map of the mouse

Genetic maps, the road maps of genetics, are of two types: linkage and physical. The 'sign posts' on the maps are loci, any location or marker in the genome that can be detected by genetic or DNA analysis. The term 'gene' is more restrictive than loci and refers to DNA segments that encode proteins or can be linked to phenotypes. Linkage maps are recombinational maps and are constructed by carrying out linkage crosses that measure the recombination frequency between genes or loci on the same chromosome.

The first genetic linkage in the mouse (and first autosomal linkage in mammals) was described in 1915 in the classic paper on the linkage of pink-eyed dilution and albino (Haldane et al., 1915)
Genetic mapping with spontaneous mutations that created visible phenotypes, such as changes in coat colour/texture or behaviour was labarious and sometimes took years because crosses between mice carrying recessive mutations yielded so few informative progeny, and genes on only one or two chromosomes could be scored in each cross.
The first real breakthrough in linkage mapping, enabling the scoring of many test markers and chromosomes in the same cross, was the discovery and use of co-dominant biochemical (isoenzyme) genes (e.g. glucose phosphate isomerase 1, Gpil; Hutton and Coleman 1969).

Current Embryology Research

Overview

Mice are highly used models of developmental biology, immunity, neurobiology, and human diseases in pathology. It's main contribution to developmental biology has been through transgenic and knockout technology which are both very important to the research of early development or organogenesis (Slack, 2006).

References

1. Dr Mark Hill 2009, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G [6]

2. Bard, Kaufman, Dubreuil, Brune, Burger, Baldock, Davidson (1998). An internet accessible database of mouse development anatomy based on a systemic nomenclature, Mechanisms of development, (74) 111-120.

3.Hedrich, H., Bullock, G., & Petrusz, P. (2004). The Laboratory Mouse. London: Elsevier Academic Press

ANAT2341 group projects

@@ Line 186: / Line 186: @@
 Genetic maps, the road maps of genetics, are of two types: linkage and physical. The 'sign posts' on the maps are loci, any location or marker in the genome that can be detected by genetic or DNA analysis. The term 'gene' is more restrictive than loci and refers to DNA segments that encode proteins or can be linked to phenotypes. Linkage maps are recombinational maps and are constructed by carrying out linkage crosses that measure the recombination frequency between genes or loci on the same chromosome.
-: The first genetic linkage in the mouse (and first autosomal linkage in mammals) was described in 1915 in the classic paper on the linkage of pink-eyed dilution and albino (Haldane et al., 1915)
+*The first genetic linkage in the mouse (and first autosomal linkage in mammals) was described in 1915 in the classic paper on the linkage of pink-eyed dilution and albino (Haldane et al., 1915)
-: Genetic mapping with spontaneous mutations that created visible phenotypes, such as changes in coat colour/texture or behaviour was labarious and sometimes took years because crosses between mice carrying recessive mutations yielded so few informative progeny, and genes on only one or two chromosomes could be scored in each cross.
+*Genetic mapping with spontaneous mutations that created visible phenotypes, such as changes in coat colour/texture or behaviour was labarious and sometimes took years because crosses between mice carrying recessive mutations yielded so few informative progeny, and genes on only one or two chromosomes could be scored in each cross.
-: The first real breakthrough in linkage mapping, enabling the scoring of many test markers and chromosomes in the same cross, was the discovery and use of co-dominant biochemical (isoenzyme) genes (e.g. glucose phosphate isomerase 1, Gpil; Hutton and Coleman 1969).
+*The first real breakthrough in linkage mapping, enabling the scoring of many test markers and chromosomes in the same cross, was the discovery and use of co-dominant biochemical (isoenzyme) genes (e.g. glucose phosphate isomerase 1, Gpil; Hutton and Coleman 1969).