Life SciencesCell BiologyDevelopmental BiologyCell DivisionEpigeneticsStem Cell BiologyChromatinDevelopmental EpigeneticsEpigenetic Regulation In DevelopmentGermline Stem CellsHistone ProteinsHistone VariantsDevelopmental Epigenetic DynamicsGermline EpigeneticsHistone Variant H3.3Histone Variant IncorporationProgenitor Cells
Stem cells can self-renew and generate differentiating daughter cells. It is not known whether these cells maintain their epigenetic information during asymmetric division. Using a dual-color method to differentially label "old" versus "new" histones in Drosophila male germline stem cells (GSCs), we show that preexisting canonical H3, but not variant H3.3, histones are selectively segregated to the GSC, whereas newly synthesized histones incorporated during DNA replication are enriched in the differentiating daughter cell. The asymmetric histone distribution occurs in GSCs but not in symmetrically dividing progenitor cells. Furthermore, if GSCs are genetically manipulated to divide symmetrically, this asymmetric mode is lost. This work suggests that stem cells retain preexisting canonical histones during asymmetric cell divisions, probably as a mechanism to maintain their unique molecular properties.
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