Cell differentiation 4

what are the main functions of the pancreas

digestion and maintaining blood sugar

what are the major specialised cell types in the pancreas

alpha cells, beta cells, somatostatin producing cells, PP cells, ghrelin producing cells

what happens in Ngn3 knockout mice

all endocrine cells fail to differentiate

what is cell fate choice determined by

cell lineage and environment, lineage defines what choices are still open to the cell, environment guides which choice is appropriate

what is the developmental origin of the pancreas

an outgrowth from the early foregut between the gall bladder and duodenum

what is required for the decision to become a pancreas

a signal from the notochord

how does the notochord signal influence the decision to become a pancreas

cells secrete Fgf2, the primordial gut cells can respond to this but are too far away, as growth of the gut occurs, one part comes closer to the notochord and is now close enough to respond to the signal from the notochord, allowing the transcription factors to switch on Pdx1

what does Cdx2 expression do

give the gut cells the potential or competence to become pre-pancreatic cells

when does Cdx2 activate Pdx1 expression

only if Fgf2 signal is received

what does the erythroid fate choice requires

GATA1

what does the myeloid fate choice require

PU.1

what do erythroid-myeloid progenitor cells express

both transcription factors, they are mutually antagonistic and do not differentiate yet

how does PU.1 repress GATA1 activity

GATA1 is bound to a target gene, PU.1 binds to GATA1, knocks off a coactivator protein, recruits chromatin methylation protein, tightens chromatin so becomes less accessible

what are some examples of the cell types in the drosophilia eye

photoreceptors, lens cells, pigment cells, structural cells, glial cells

what is the effect of a mutation in the PAX6 gene

the whole eye is missing, not just one cell type

what does the PAX6 gene do

encodes paired box and homeodomain transcription factor and is expressedin the early anterior ectoderm, this one transcription factor sets off the whole process so when it is mutation, the anterior ectoderm never becomes the eye primordium so the eyes don’t develop at all

what is the effect of expressing PAX6 in the wrong locations

there becomes extra eyes where each leg or wing should be

what does the case of pax6 demonstrate

that a single transcription factor can determine the identity of a whole organ

what does loss of one pax6 gene cause

aniridia, loss of the iris, defective retina, optic nerve, cornea, cataracts form very quickly