B cell lymphoma 6 (Bcl6) is a proto-oncogene functioning as a transcriptional
repressor at the germinal centre (GC) stage of B cell development, regulating
proliferation, differentiation and survival. Bcl6 is commonly dysregulated in GCderived
lymphomas and hence a promising therapeutic target. Although a
number of agents targeting Bcl6 are being developed, there is currently no
good model available for functional analysis and hence drug target validation.
To address this issue, I have established a conditional BCL6 knockout cell line
for in-depth functional analyses of Bcl6. I have used homologous recombination
to disrupt one BCL6 allele in the human Burkitt’s lymphoma cell line DG75 with
a zeocin resistance cassette and have shown this line to be capable of
supporting tetracycline (tet)-regulated Bcl6 expression from an integrated
expression construct. The zeocin cassette used to disrupt the first BCL6 allele
was subsequently deleted by Cre recombination. This allowed me to reuse the
same targeting construct to disrupt the second BCL6allele. I subsequently set
out to characterise the resulting conditional knockout cell line and found that
depletion of Bcl6 leads to less proliferation, characterised by a prolonged
G0/G1cell cycle phase. I went on to further characterise the effect of Bcl6
depletion in my system by cDNA microarray analysis, which revealed
interesting insights into functions of Bcl6 such as the modulation of B cell
receptor signalling and calcium signalling. The system I have developed is the
first precisely regulated genetic model for studying Bcl6 function and will be of
great benefit for research aiming to develop Bcl6 targeted drug therapy.