Bio 1-L17- Appropriate Cell Differentiation and the Importance of time and Space

what is important for cell differentiation

• time- notch signalling- differentiation is progressive and coordinated

• space- hippo- positional information

how is gene expression detected in the embryo

• transcriptonomics- RNA sequencing

• PCR- amplification of RNA

• in situ hybridisation- where and when a gene is present using signals/probes

what is in situ hybridisation? what is used? and why is it used?

• visualises when and where master control genes and expressed. it is important for cell lineage/cell fate analysis

1. a probe that binds to RNA

2. reporter genes such as GFP

what is time?

time is when a cell goes through its journey and it becomes more restrictive until its fate is determined.

difference between specification and determination

• specification- early commitment- but still can be reversed

• determination- has fixed its fate

what is lateral inhibition and example

ensures all cells in a similar field of cells do not undergo differentiation at the same time

• in mice- when a cell differentiates it exhibits inhibitory cells to tell the cells around it not to differentiate the same way

delta notch pathway- and example

• how cell decides to become a neuron or not- JUXTACRINE

1. continuous neural plates- show delta, notch and neurogenins

2. one has more delta- which inhibits the other from doing the same

another example of juxatcrine signalling?

• in c.elegans-differentiation of different parts of the vulva

• the 2nd signal is sent out from inner vulva to tell the outer vulva not to differentiate into the same cell type as the inner vulva through Notch signalling

how do cells receive positional information? is it time/space? and examples for each

• asymmetrical cell division- different daughter cells- in drosphila- maternal effect genes- establish poles (bicoid)

• induction- cell-cell signalling- adjacent cells tells cells around It what to do- notch, Wnt and FGF

• morphogens- concentration of signal determines the cell fate- concentration of bicoid in drosophila

• biophysical cues- in bone development- YAP is expressed in developing bone to determine shape

what is a morphogen

a signal involved in pattern formation- cells have a graded response depending on level it is exposed to

examples of morphogens

• bicoid in drosophila- role in axis establishment

hippo signalling pathway- yap/taz

• Hpo/Lats 1/2- phosphorylated- Yap/tazcannot enter nucleus and control gene expression

• Hop/Lats 1/2- unphosphorylated- Yap/Tazenters nucleus and controls gene expression

• wild type- smaller, mutated- bigger increased size- Yap/Taz is always on

how is cell lineage analysed and examples?

1. GFP- insert it into specific locations of DNA- used in zebrafish and c.elegans to visualise specific neurons

2. XFP’s- different colours engineered to see many cell fate lineages- ie brainstorm in mouse brain

drosophila development is important for?

1. cytoplasmic determinants- products of maternal effect genes is localised to one side for pole axis

2. morphogens- the product of maternal genes- bicoid is on one side more which determines the hed

3. cell signalling- segmentation genes Wnt and Hedgehog divide the embryo

4. homeotic genes- such as how genes help the correct development of body parts in the right places

biophysical cues- what and who did the experiments to show these?

• it shows that physical movement of embryos ie chick- determines how a body part will form

• it is seen in knee development- when movement is lower- YAZ is in lower concentration and changes bone shape

• Enger et al- studied that soft substrate- nuerons and hard substrate- bones