Human Embryology and Developmental Biology – Lecture 3
15-02-2018
Fundamental molecular processes in development, are:
- Cell specification
- Induction and cell determination
- Fate mapping
- Morphogenesis
- Morphogens and positional information
Cell Specification:
- Autonomous
- Conditional
- Syncytial
See lecture 2
Morphogens and positional information:
Positional information is used by embryonic cells to differentiate in a certain
direction.
1. First, the cells acquire an identity or positional value that is related to their
position in the embryo
2. Second, the cells interpret this information and differentiate according to their
genetic program.
Morphogen: a soluble chemical molecule that provides positional information. A
combination of different morphogens + different gradients of each morphogen,
determines what a cell will be(come).
The combination of multiple morphogen gradients defines the mode of pattern
formation. The general mode of pattern formation can be illustrated with use of the
French flag model.
French flag model: Different gradients different thresholds.
, Positional information can be used to draw/generate 2D patterns.
- Cells, not under influence of morphogens, stay in their default stage
ectoderm = epidermis.
Examples:
- Activin turns cells into different types of mesoderm, depending on the
concentration.
Different types of activin/morphogens initiate different types of gene expression.
Depending on the concentration, different genes will be expressed.
Induction of mesoderm by the vegetal region in Xenopus blastula:
Different parts of the vegetal hemisphere induce different mesoderm;
- Dorsal vegetal cells induce dorsal mesoderm (muscle cells, notochord +
neural tube)
- Ventral vegetal cells induce ventral mesoderm (mesenchyme + blood cells
surrounded by epidermis)
This indicates that different signals are given from the vegetal cells at dorsal and
ventral side.
Mesoderm is formed after interaction between the animal cap and vegetal pole cells.
15-02-2018
Fundamental molecular processes in development, are:
- Cell specification
- Induction and cell determination
- Fate mapping
- Morphogenesis
- Morphogens and positional information
Cell Specification:
- Autonomous
- Conditional
- Syncytial
See lecture 2
Morphogens and positional information:
Positional information is used by embryonic cells to differentiate in a certain
direction.
1. First, the cells acquire an identity or positional value that is related to their
position in the embryo
2. Second, the cells interpret this information and differentiate according to their
genetic program.
Morphogen: a soluble chemical molecule that provides positional information. A
combination of different morphogens + different gradients of each morphogen,
determines what a cell will be(come).
The combination of multiple morphogen gradients defines the mode of pattern
formation. The general mode of pattern formation can be illustrated with use of the
French flag model.
French flag model: Different gradients different thresholds.
, Positional information can be used to draw/generate 2D patterns.
- Cells, not under influence of morphogens, stay in their default stage
ectoderm = epidermis.
Examples:
- Activin turns cells into different types of mesoderm, depending on the
concentration.
Different types of activin/morphogens initiate different types of gene expression.
Depending on the concentration, different genes will be expressed.
Induction of mesoderm by the vegetal region in Xenopus blastula:
Different parts of the vegetal hemisphere induce different mesoderm;
- Dorsal vegetal cells induce dorsal mesoderm (muscle cells, notochord +
neural tube)
- Ventral vegetal cells induce ventral mesoderm (mesenchyme + blood cells
surrounded by epidermis)
This indicates that different signals are given from the vegetal cells at dorsal and
ventral side.
Mesoderm is formed after interaction between the animal cap and vegetal pole cells.
