Asymmetric Division of Drosophila Male Germline Stem Cell Shows Asymmetric Histone Distribution

Epigenetic Inheritance A long-standing question is whether and how stem cells maintain their epigenetic information. Knowing that many types of stem cells undergo asymmetric cell divisions, Tran et al. (p. 679 ) probed the asymmetric division of Drosophila male germline stem cells and found that preexisting histones were selectively segregated to the stem cell, whereas new histones were enriched in the daughter cell that underwent differentiation. By contrast, asymmetric histone distribution was not seen in progenitor cells. This study suggests that stem cells retain preexisting canonical histones during asymmetric cell divisions in vivo.