Stem Cells Flashcards
give an example of ES cell transfection
mouse sp8 gene expressed in neuroepithelium - limb buds, heart etc
sp8 deletion = limb truncation and failed neuropore closure
in vertebrates - Fgf8 expressed in AER - cells responsible for limb outgrowth - knockout = limb truncation
what are some solutions to graft problems?
mobilise peripheral blood stem cells - remove WBCs from donor blood, RBCs returned
WBCs contain some peripheral BCs - mobilise with SCs from BM with daily injections of granulocyte colony SF
increases SC population - aids engraftment
many diseases treated, lymphoma, leukaemia, solid tumours
what are autografts?
autologous haematopoeitic SCs require HSC extract from patient and cell storage in liquid N
BM ablated with chemo to eradicate malignant cells
frozen cells used to repopulate BM - standard lymphoma treatment
must remove cancer cells from BM - find areas free of cancer
what is the problem with immunorejection of xenografts?
mouse host rejects human cells
developed mice without T cells - longer graft survival but IS remained - some cells such as NK
what is epigenetics?
heritable traits excluding a change in underlying DNA sequence
involves change in chromatin structure
all cells inherit same dNA seq - so cell differentiation relies on epigenetics rather than genetic inheritance
describe the 3 cell lineages and the concept of potency
endoderm, ectoderm and mesoderm
Thomson et al 1998 proved potency by injecting cells into mice - teratoma growth with many cell types
hay flick et al 1974 - finite number of expansions before non dividing senescent state
high amount of telomerase = immortality
what are the main concepts of epigenetic regulation?
DNA methylation - marks cpG bases/represses gene activity
histone modification - alter activity of genes wrapped around
remodelling - tightly packed het c can prevent transcription factors accessing cis elements
loosely packed euchromatin allows TFs to access cis elements (DNA seq)
what are some effects of HOX gene patterning?
polydactyly caused by disrupted Hox D 13 - knockout - lumbar vertebrae = ribbed
nanog may block differentiation effect of Oct 4 - maintains Oct 4 transcription - not down regulated unless cells differentiated
dimerisation domain - 2 TFs bind = functional dimer - adds versatility
what are the consequences of driving key transcription factors in adult dermal fibroblast?
cell starts producing own key embryonic TFs
epigenetic regulation
changes cell ID from adult cell with restricted fate to something like ES cell
How could iPs cells be created without viral delivery?
reprogram cells - combination of yamanaka TFs - SoX2, Oct 4m klf4, CMyc
add small molecules that interfere with maintenance of epigenetic markers - can boost reprogramming
changing epigenetic regulation = key to making iPs
How did Takahashi et al (2007) bypass ethical worries?
ID’d main TFs controlling ES cells - force mature cell into embryonic like state
used viruses to introduce TFs to skin fibroblast - cultured - 4 retroviruses silenced in human iPs - cells efficiently programmed independently of continuous expression of transgenes for self renewal
iPs cells totipotent and can engineer any cell type - like ES cells
