BGM1004/L22 Vertebrate Development Flashcards
When does patterning occur?
Initiated on day 12
What is morphogenesis?
Process by which an organism or structure begins to develop 3-dimensional form
Give the 3 fundamental processes of developmental biology.
Morphogenesis
Cell differentiation
Growth
Define axis formation.
Establishment of body plan
What is body plan?
Map of an organism developed by three axis
Give and define the 3 axis.
Antero-posterior axis - head to tail
Dorso-ventral axis - back to belly
Left-right axis - as stated
Give another name for the anterior end of the embryo.
Rostral
Cranial
Give another name for the posterior end of the embryo.
Caudal
What is body axis formation dependent on?
Different parts of the embryo becoming distinct
Name the 4 components to cell signalling.
Release and transmission of signal by source cell
Reception by target cell
Transduction
Cellular response
Give 2 example of cellular responses to cell signalling.
Differentiation
Proliferation
Cell shape change
Migration
Death
What signalling molecules pattern the embryo?
Growth factors/ morphogens
How do morphogens control positioning of specialised cell types?
Form gradients which activate/repress different genes at different concentrations
What is the role of the protein bicoid in flies?
First step in establishing A-P polarity
Give 2 ways that morphogens achieve long range signalling in cellularised tissues.
Diffusion over long distances
Relay from cell to cell
Cellular extensions
Describe the role of the Sonic Hedgehog (Shh) protein.
Crucial vertebrate morphogen
Name the 2 main signalling centres in early mammalian embryos.
Anterior visceral endoderm (AVE)
Node (organiser)
What gene is crucial for the formation of the anterior visceral endoderm?
Lim-1
Name 3 genes that severely affect body plan when knocked out.
Lim-1
Chordin
Noggin
Shh
Where does breaking of left-right symmetry first occur?
At the node
Name 2 morphogens involved in left-right axis formation.
Shh
RA
FGF
Describe how morphogens create left-right axis in vertebrates.
Activates specific signalling pathway only in left side
Describe the L-R signalling pathway (4)
Initiated at node
Release of morphogens
Nodel signalling activated on L side
Nodal activates Pitx2
Downstream gene expression activated
Which side of the body is default?
Right side - left actively specified
What is the role of Homeobox gene Pitx2? (2)
Regulates downstream gene expression
Governs asymmetric organ development
What tools are used to determine L-R patterning? (2)
Physical inversion and transplantation of node
Genetic knockout of Lefty-1 or Shh gene
What occurs when Lefty-1 or Shh are knocked out?
Both sides present as ‘left’
What occurs when the nodal is on the right side of the body?
Situs inversus totalis
Total inversion of organs
No effects
What occurs when the nodal is on both sides/ neither side?
Left isomerism
Right isomerism
Poor prognosis
What occurs in situs inversus thoracalis?
Thoracic organs are inverted
Poor prognosis
What occurs in situs inversus abdominalis?
Abdominal organs are inverted
Poor prognosis
What is the role of Wnt in AP axis formation?
Specifies early anterior region
What is the role of RA in AP axis formation?
Patterns midbrain, hindbrain and trunk
What is the role of FGF in AP axis formation?
Patterns the caudal region
Which genes code for vertebrae with/without ribs?
Hox6
Hox10 respectively
Which 2 morphogens determine neuronal sub-types? By which mechanism?
Shh and BMP
Opposing gradients
Describe the patterning of the neural tube.
BMP and Wnt determine from dorsal region
Shh determines from vental region
Where are the signals required for limb outgrowth?
Apical ectodermal ridge (AER)
What morphogen principally determines limb outgrowth?
FGF8
How does thalidomide disrupt limb patterning? (3)
Stops production of blood vessels
Blocks proliferation
Alters expression of Shh, FGF and Hox genes
SALL4 mutations have been shown to cause what syndrome?
Duane Radial Ray Syndrome
How do teratogens act?
Disrupt patterning signals and genes
