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The transcription factor C/EBPα reprograms B cells into macrophages by “short-circuiting” the cells so they re-express genes reserved for embryonic development, according to research published in Stem Cell Reports.
Over the past 28 years, researchers have shown that a number of specialized cell types can be forcibly converted into other cell types, but the science of how this change takes place is still emerging.
“For a long time, it was unclear whether forcing cell fate decisions by expressing transcription factors in the wrong cell type could teach us something about what happens normally during physiological differentiation,” said Thomas Graf, PhD, of the Center for Genomic Regulation in Barcelona, Spain.
“What we have now found is that the two processes are actually surprisingly similar.”
The researchers found that B-cell transdifferentiation takes place when C/EBPα binds to two regions of DNA that act as gene expression enhancers. One of these regions is normally active in immune cells, and the other is only turned on when macrophage precursors are ready to differentiate.
This indicates that the convergence of these two enhancer pathways can cause the B cell to act like a macrophage precursor, thus triggering the unnatural transdifferentiation.
“This has taught us a great deal about how a transcription factor can activate a new gene expression program (in our case, that of macrophages) but has left us in the dark about the other part of the equation; namely, how the factor silences the B-cell program, something that must happen if transdifferentiation is to work,” Dr Graf said. “This is one of the questions we are focusing on now.”
Dr Graf is interested in this pathway because C/EBPα-induced, B cell-to-macrophage transdifferentiation can convert both human B-cell lymphoma and leukemia cells into functional, non-cancerous macrophages.
He believes that induced transdifferentiation could become therapeutically relevant if a drug could be found that can replace the transcription factor. And understanding the mechanisms of the process could help labs that use this transdifferentiation approach to generate cells for regenerative purposes.
