Epigenetic control of pluripotency in Drosophila primordial and ovarian germ line stem cells

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Analysis of histone modification marks revealed specific epigenetic processes in PGCs and GSCs. Like in blastoderm also in PGCs chromatin differentiation is polar. H3K4me1 and H3K27me2/me3 are abundant and the SU(VAR)3-3 demethylase ensures a low level of H3K4me2 in PGCs. Su(var)3-3 mutations impair stemness and development of GSCs. The heterochromatic H3K9me2/me3 marks are controlled by SETDB1 in PGCs and by SU(VAR)3-9 and SETDB1 in GSCs. Abundant chromatin proteins in PGCs are SU(VAR)3-3 and SU(VAR)2-1 associating into an early chromatin protein complex. SU(VAR)2-1 is a novel factor essential for PGC and GSC development. Chromatin differentiation in PGCs is under control of ecdysone signaling. Genetic dissection of gene silencing in germ line stem cells revealed complex epigenetic programming and proved the function of many known epigenetic factors in these processes. In our future work we will focus on defining and functional analysis of epigenetic factors which control histone modifications in germ line stem cells. In our analysis of epigenetic processes in germ line stem cells we will combine genetic techniques with ChIP analysis of germ line chromatin.