Effect of activated mNotch1
expression on the differentiation and proliferation of 32D cells. The
parental 32D line (WT) and 32D cells transduced with the pLXSN
retrovirus, pLXSN containing the active region of the intracellular
domain of mNotch1 (mNotch1-ICΔOP), or a pLXSN-mNotch1
control lacking the cdc10 repeats (mNotch1-ICΔOPΔCDC) were
evaluated for growth and differentiation in response to G-CSF. This
figure represents one of four experiments, all having comparable
results. (A) The relative percentages of viable cells
remaining undifferentiated (○) or showing morphologic
characteristics of mature granulocytes (▪) after successive
days in culture. Plots for the retroviral lines represent the averages
of four (LXSN) or six (mNotch1-ICΔOP and mNotch1-ICΔOPΔCDC)
individual clones. Error bars = SEM for each set of clones; error
bars are not included on the WT graphs since these represent a single
population. (B) Representative Wright-stained cells. IL-3,
undifferentiated parental 32D (WT) cells maintained in medium
containing 10% WCM as a source of IL-3; G-CSF, 32D WT cells and
representative clones expressing pLXSN, pLXSN-mNotch1-ICΔOPΔCDC or
pLXSN-mNotch1-ICΔOP after 6 days in medium containing 1% WCM and 10
ng/ml G-CSF. The cells depicted in the second and fourth panels (32D
WT and mNotch1-ICΔOPΔCDC) represent a single field condensed by
deleting vacant areas to show a greater number of cells. The white and
black arrows indicate band forms and segmented neutrophils,
respectively. (C) The proliferation of undifferentiated
cells (○) and mature granulocytes (▪) after
successive days in culture with IL-3 (32D WT, Upper) or
G-CSF. The total number of undifferentiated cells and mature
granulocytes relative to the original number of cells plated are
compared for the 32D parent line (WT) and each set of retroviral
clones. Again the graphs represent the averages of four (LXSN) or six
(mNotch1-ICΔOPΔCDC and mNotch1-ICΔOP) clones. SEMs were small;
error bars are not depicted for the sake of clarity and would not
change the impression created by the figure. Cells showing some
characteristics of differentiation, but which were less mature than
band cells were not included in either the undifferentiated or mature
categories.