intro to DevSteR Flashcards
what’s Developmental biology
-the study of the process by which animals and plants grow and develop
-It also involves the study of tissue homeostasis in adulthood (mechanisms important in embryo are maintained in adult hood)
what are stem cells
found in the embryo and also in adults. Stem cells are also studied in vitro to aid in regenerative medicine
-highly studied- cultured in petri-dish and differentiate into different cells
-produce progeny with different cell type
what does The study of regenerative biology aim to do
-aims to elucidate the innate ability of organisms to replace tissues or organs after they have been removed or damaged
why are model organisms used in DevSteR studies
- complex interactions within the whole organism
- genetics
- surgical accessibility- doesn’t kill animal but you can surgically look at it
- low cost
- ethics - restricted for vertebrates
- genome sequencing- so you can look at sequence of protein for its function
- shared methods and knowledge worldwide - without this= very slow progress
what are Cell fate maps
-what essentially that cell will turn into
- Early on in the embryo, cells all look the same.
- But they may already be fated to give rise to a certain structure or cell type
- Sometimes we can watch patiently for days to follow a cell and its offspring to see what it forms (C.elegans)- label cells with dye put embryo away then look later to see what the cell gives rise to- about 1000 cells
- Otherwise, we need to label the cell so that we can follow the cells for days, weeks or longer
what are Fate maps
-8 cells in embryo
-inject dye into cell B
-B is specified to become muscle in the tail of fish
-signal received by cell telling into be muscle or does it already know to be muscle (committed irreversibly)
-inject dye into cell C
-C is specified to become eye cells
-lineage tracing
whats Cell fate commitment and plasticity
-take dyed b cell from one embryo and place it in the place of c of another
-2 b cells
-B remains committed to muscle fate. B has been determined by intrinsic factors such as a transcription factor.
-Perhaps the fish would have extra muscle and less eye tissue
-or B has been reprogrammed to C’s cell fate.
This suggests that cell signalling is taking place so that the transplanted cell knows its position- cell signalling in place C
what are Induction (instructive) signals
-dyed D cell put into another embryo in place of A cell- ectopic signalling source
-duplicated D cell
- The fish has less muscle and an extra eye
- This suggests that D is a signalling cell that induces eye cell fate
- These types of experiments that involve physical manipulation of the embryo are called embryology
What do we mean by cell signalling?
- Signals (ligands) are secreted (as proteins) by signalling cells and usually do not pass through the cell membrane
- Specific receptors need to be present on the cell membrane to transduce the signal into the cell
- In this example B and C are competent (receptive) to receive the signal from D because they both express the receptor
- Signal transduction often results in activation of a transcription factor
- There are many exceptions to these rules
-C cell has very specific recs
-lots of signals made by D cells which can’t pass through membrane to neighbouring cell (can’t bind to recs)
how can cell signals have different activities
-patterning cells: a signal can cause identical cells to adopt different fates as they develop - cells are similar and not differentiated therefore adopt different cell fates
-cause cells to proliferate (eg FGF Lecture 3)
-cause cells to live or die (eg Growth Factors)
-allow or block cells from responding to other signals (eg permissive signals)
-attract or repulse cells during migration (eg chemoattractants)
-regulate cell metabolism (eg insulin) etc
-Signal pathways often can have more than one activity
whats Gene expression analysis
- Expression analysis tells us about what is happening within a cell or regionally within a tissue
-all have same genes, its which ones are activated which make it different
-RNA in situ hybridisation stains cells blue/purple if they express the RNA for a particular gene - Antibody staining is a technique that uses antibodies to detect where specific proteins are expressed
-The edge of the limb bud expresses FGF4 which is a signal- drives proliferation
-Actin staining (in green) shows the cytoskeleton of these two cells- Fluorescent labels give very high contrast
whats Genetic and ectopic expression analysis
-Since mutations that remove FGF genes result in limbless mice, we know that FGFs are required for limb development. Mouse is a good model for genetic analysis because we can do genetic engineering.
-implant a bead soaked in FGF protein between the limb buds
-This results in a chick embryo with an ectopic limb. This shows that FGFs are sufficient to induce limb formation (in the flank of the embryo).
