WEEK 3 Flashcards
LOOK OVER NOTES ON:
Metabolism and its control (2) and Structure and Function of connective tissue (+histology)
What are the key cellular processes in making a human?
Cell division (expansion) Cell death (elimination) Cell differentiation (specialisation)
What is cell differentiation?
What proteins a cell expresses and how cells interact with the outside world as a result
What is cell potency?
The ability of a cell to differentiate into different cell types (more cell types=greater potency)
Different types of stem cells written in order of decreasing potency
Totipotent (zygote)->Pluripotent (embryonic stem cell)->Multipotent (bone marrow stem cell)->Unipotent (tissue)
What happens to stem cells when they are not differentiating?
Self-renewal (maintenance)
What is a progenitor?
Intermediate cells of cell differentiation from stem cells which undergo expansion and form terminally differentiated cells
How is cell differentiation controlled?
Gene expression control, some activated/some inhibited
Give the control of RBC and platelet differentiation
stem cell->erythroblast->reticulocyte->RBC w/ cell specific proteins (alpha/beta globulins/spectrin/carbonic anhydrase)
stem cell->megakaryoblast->megakaryocyte->platelet w/ cell specific proteins (thrombin/collagen/fibrinogen receptors)
What factors control gene expression?
Transcription factors
What do transcription factors bind to on the DNA sequence?
Gene regulatory sequences-enhancer and promoter regions
What effect does binding of TF to gene regulatory sequences cause?
RNA polymerase transcribes DNA, forming mRNA
What two domains do TFs have?
DNA-binding domain (binds to enhancer/promoter regions) Activation domain (interacts with RNA polymerase resulting in gene transcription)
How are different steps of differentiation controlled?
By different transcription factors
How are transcription factors controlled?
Extracellular signals
Detail the Erythropoietin cycle
Low O2 in PCT->Epo->Bone marrow->stimulates stem cells into RBC progenitors->RBCs
Explain the process of Epo regulation of RBC-specific genes
Epo binds to Epo receptor in cell membrane of haematopoietic stem cells, activates gene regulatory proteins, binds to regulatory DNA, promotes activation of gene to produce another protein, protein binds to other regulatory regions, generates proteins required for RBCs
How does deregulated differentiation processes cause disease?
Stem Cell—>Precursor-X->B cell
inability to differentiate to terminally differentiated cell causes proliferation of precursor=tumour (eg. B cell acute lymphoblastic leukaemia)
What is an induced Pluripotent Stem Cell (iPS)?
A pluripotent stem cell generated from a unipotent stem cell via activation of certain deactivated genes
