Introduction Flashcards
Diseases connected to developmental defects.
polydactyly (abnormal digits)
microcephaly (depletion of CNS stem cells)
situs inversus (defective lateralization)
Treacher Collins syndrome (abnormal crest cell migration)
Causes of congenital abnormalities - when and which?
when = intrauterine development
- genetic
- maternal infectons (rubella, zika, syphillis)
- maternal nutritional (folic acid, iodine)
- environmental (alcohol, tobacco, pesticides, radiation)
SPIM microscopy
selective plane illumination microscopy
(same as light sheet fluorescence microscopy)
- planar illumination of focal plane from the side
- only a thin section at a time = minimal photodamage
- optical sectioning -> better resolution
Spemann-Mangold organizer experiment
dorsal lip of blastopore transplanted to the blastocoel roof
induces secondary axis formation, neuralization
dorsalization of ventral mesoderm -> somite formation
What is an organizer?
What is primary organizer?
organizer:
region of the embryo
capable of determining the differentiation of other regions
primary organizer:
dorsal blastopore lip
What does it mean if the cell fates are determined?
can differentiate autonomously when placed in a different part of the embryo
What is a cell fate?
commitment to a cell type
specification ->
determination (by transcriptome and proteome on molecular level; maintained by epigenetics) ->
differentiation
What is the role of morphogen gradients in development?
- red out of positional information acording to the shape of the gradient
- cell fate is induced by a threshold of morphogen concentration (French flag model)
Explain the french flag model.
localized source of morphogen +
+ degradation at its sink
= creating a gradient of morphogen throughout not yet differentiated tissue
–> cells sense whether they are above or below the threshold
–> become specified and differentiate by turning on target genes
boundaries correspond to thresholds exactly
Examples of cells reading out morphogen concentration.
- limb bud organizer –> digit identity
- neural tube patterning –> roof and floor plate
How do cells interprete graded signals? How do they read out the gradient?
- binding site affinity
- combinatorial input
- reciprocal repressor gradient
What affects cell fate decisions besides morphogen gradient? Examples.
direct cell-cell contact (adhesion & repulsion)
- -> sorting of cell types into regions based on quantity and type:
- CNS = N-cadherin
- epithelial cells = E-cadherin
- placenta = P-cadherin
- retina = R-cadherin
Example of cell sorting in development.
Neural tube formation:
- Presumptive epidermis with E-cadherin
- neural tube with N-cadherin
- invagination and neural tube closing
Define gastrulation.
Define morphogenesis.
Gastrulation = transformatio/rearrangement/movement of cells
Morphogenesis = formation of a feature during development, driven by EMT and MET
Difference between epithelial and mesenchymal cells.
Epithelial: tightly connected, stationary, function as a unit
Mesenchymal: loosely connected, mobile, independend of each other
