Lecture 3 Flashcards
What are the 3 steps for a cell to acquire its fate?
Specification: knows it is programmed for a certain fate but is still responsive to cellular cues.
Determination: knows it is programmed for a certain fate but is not responsive to external cues.
Differentiation: Acquires its fate
What are the three types of specifications?
Autonomous, conditional and syncytial.
What are the 2 types of development?
Mosaic (intrinsic factors) and regulative (cell-cell interactions = outside-in development)
What are the 3 rules of evidence?
Find it = correlation, be careful
Lose it = necessity
Move it = sufficiency
What is autonomous specification? Give examples.
Autonomous specification occurs through mosaic development: cells acquire their fate due to intrinsic factors, generally maternally loaded ones.
Ex: limpets trochoblasts, germ line specification in c. elegans embryos from P granules containing cells. Predominates in invertebrates.
What is conditional specification? Give examples.
Occurs through regulative. development: cells acquire their fate due to extrinsic factors like it’s position within embryo and signals from other cells.
Ex: Sea urchin 4 blastomeres where when you alter the planes of cell division to change the distribution of cytoplasmic determinants and still get a normal larvae. Case of identical twins. Moving of cells in a zebrafish embryo and cells still acquire the right fate. Predominates in vertebrates.
What are the 4 types of extrinsic signals?
Endocrine (hormones = large distance, need blood)
Paracrine (distance = microns, act as morphogens and activate signal transduction pathways)
Autocrine
Juxtacrine (Delta-Notch, Ephrin-Ephrin receptor)
What are the major four morphogens?
- Fibroblast Growth Factors family (FGF - FGF receptop - RTK transduction pathway).
- Hedgehog family (hedgehog - patched receptor - hedgehog signal pathway)
- Wnt family (Wnt - Frizzled - Wnt signal pathway)
- Transforming Growth Factor beta family (SMAD pathway)
What is the role of morphogens?
Their concentration can deterine cell fates: it is sufficient to induce spatial patterning in Xenopus embryo cells where high [activins] = dorsal, lower = muscle, none = heart and blood vessels.
What is syncytial specification?
Nucleus multiply without cytokinesis. Position of nucleus compared to concentrations of caudal and bicoid morphogens lead to axial patterning. Predominates in most insect classes.
