WEEK 1-2: Vertebrate Embryology and Animal Developmental Biology Notes

Animal Developmental Biology

study of embryonic developmental processes of integrated complex phenomena

Embryo

early stage when the developing animal does not yet resemble the adult of the species

Fertilization

birth, hatching, metamorphosis (development)

Ontogenic

processes that are involved in the transformation of a fertilized single oocyte into a new organism

Growth

generation of cell number

Differentiation

Cellular diversity within generation

Morphogenesis

cellular order within generation

Mosaic development

where the fate of a cell depends upon specific cytoplasmic determinants in the zygote

Regulative development

where the fate of a cell depends upon interactions with neighboring cells, not on what piece of cytoplasm it has

Phylogenetic

transformation of the forms of life (evolutionary development)

Pattern formation

(body axes formation)

Problem of Differentiation

How does the same genetic information results to different cell types?

Problem of morphogenesis

How do cells form ordered structures?

Problem of growth (cell division)

How are cell division and growth tightly regulated?

Problem of reproduction

How are reproductive cells set apart during embryonic development?

Problem of evolution

How do changes in development create new body forms and what changes are possible?

Environmental integration

How does the organism's phenotype influenced by the environment?

Guidelines

directive influences on development

Preformed guidelines

present right at the start of ontogeny; maternal genes/maternal effect genes

Progressively formed guidelines

appear gradually in every step of ontogeny; zygotic genes

Maternal genes/maternal effect genes

distribution of key maternal factors in the oocytes (maternal mRNA)

Balbiani body

accumulation of mitochondria and cytoplasmic granules (germ granules) containing silenced mRNAs

Maternal mRNAs

are organized in the cytoplasmic granules together with several regulatory proteins responsible for their post

Vegetal pole

is the end with the highest concentration of yolk

Cleavage

pattern is under mother's control

Blastula

participants of father's genes, new sets of genes, new proteins synthesized

Gastrula

new sets of genes, new proteins synthesized

Anterior

posterior axis

Developmental potential

inducing properties of cell in the dorsal lip of blastopore (DLB) change with time

Early cells in the DLB

→ anterior mesoderm → neural tissue

Latter cells of the DLB

→ posterior → induce posterior neural structures

Wnt signal activity

high in posterior; low in anterior

Gap genes

define broad territories of the embryo; enable the expression of the pair

Pair rule genes

divides the embryo into regions about two segments wide

Segment polarity genes

divide the embryo into segment

Homeotic genes

define the identities of each of the segments in the spatial domain

Fate

the range of cell types that a particular embryonic cell can give rise to

Potency

the ability of a cell to follow a developmental pathway

Embryonic stem cells

unspecialized; can undergo unlimited self

Totipotent

total potential of any cell

Pluripotent cells

can differentiate into any body tissue; it cannot support full development of the entire organism/embryo

Multipotent

differentiates into different cell types within given lineage

Unpotent

fully specialized; can generate its own specific type

Determination

the gradual commitment to a certain cell fate; geared to follow a certain developmental pathway

Embryonic induction

evocative influence of cells

Chordamesoderm

the capacity to induce

Ectoderm

competence to respond

Regulation of developmental process

it is the precise control of gene expressions, cell

Gene regulation

control of gene expression; specific genes turned on or off at precise times

Cell signaling pathways

pathways play a crucial role in cell

Epigenetic modifications

can influence gene expression without altering the DNA sequence, an additional layer of regulatory control over developmental processes

BMP/TGF signaling pathway

signals through SMAD proteins

FGF signaling pathway

activates the MAPK and Akt pathways

Wnt signaling pathway

promotes pluripotency

Notch signaling pathway

controls cell fate during animal development

Hedgehog signaling pathway

plays a key role in determining cell fate during embryonic development

Apoptosis

programmed cell death in mammalian tissues

PCD

is an important process during embryonic development

Sculpting

hollowing out to create lumen or cavities; formation of tubes and vesicles

Biological clock

the somite segmentation clock

Somites

repeated structures in embryogenesis; they are sequentially generated

Oscillatory genes

oscillate every 2

Cell intrinsic timers

intracellular developmental programs that change precursor cells over time

Intrinsic timing mechanism

helps determine when cells stop dividing and differentiate

Signaling factor (PDGF)

serves as timer component and measures elapsed time

Effector (TH)

stops cell division; initiates differentiation at the appropriate time

p27/Kip1

a cell cycle inhibitor accumulates in the precursor cells as they proliferate

Homeobox genes

the master developmental control genes; act at the top of genetic hierarchies, regulating aspects of morphogenesis and cell differentiation in animals

Descriptive embryology

involves detailed study of the structure and arrangements of minute internal organs

Comparative embryology

establishes relationships between developmental stages

Experimental Embryology

finds out why a process is carried out at a specific time in a specific manner

Chemical embryology

involves biochemical investigations of the embryo; ushered in molecular biology

Tertology

study of embryonic malformations

Reproductive embryology

techniques in fertilization, implantation of embryos; concepts of conception and contraception

Developmental biology

broader approach from embryonic development to postnatal development

Aristotle

1st systematic study of embryos; recorded different stages in the development of the chick embryo; recognized that there are multiple ways that organisms reproduce

William Harvey & Graaf

described the ovarian follicle and Graafian follicle

Hamm & Leuwenhoek

observed human sperm; laid down the theory of preformation

Splanzani

states that both male and femlae sex products are necessary for the initaiation of development

Wolff

states that embryological development occurs through progressive growth and development; laid down the epigenetic concept; theory of epigenesis

Lazzaro Spallanzani

successfully performed the first artificial insemination (using frog eggs)

Caspar Wolff

first person to demonstrate morphogenesis; saw the development of structure out of structureless materials

Karl Ernst Baer

made significant strides in descriptive embryology searching for the vital force; the first person to note the many similarities between the embryos of vertebrates, particularly amniotes

Karl Ernst Von Baer

father of embryology

Von Baer's Law

the more general features that are common to all members of a group of animals developed earlier than the more special features which distinguish the various members of the group

Ernst Heckel

laid down the concept that ontogeny recaptulates phylogeny

Law of biogenesis

ontogeny is a shortened/modified recaptulation of phylogeny

Christian Panderm

existence of germ layers

Heinrich Rathke

affinity between embryos of higher and lower vertebrates (pharyngeal pouches)

Schleiden & Schwann

laid the foundation of Modern Embryology & Histology

Wilhelm Roux

founder of experimental embryology; he began in the 1880s an experimental program using frog eggs

August Weismann

the germplasm theory; self

Oscar and Richard Hertwig

was the first man to observe sexual reproduction

Hans Spemann and Hilde Mangold

introduced the organizer effect (dorsal lip of blastopore) and concept of embryonic induction

Edward & Sleptoe

introduced IVF

cdx2

are expressed in the blastoderm, and affect the vegetal

oct4

is restricted to the cells of the inner cell mass, which generate the embryo proper

Embryo

Early developmental stage before resembling adult form.

Vertebrate Embryology

Study of vertebrate embryo development processes.

Animal Developmental Biology

Study of structural changes in animal embryos.