Stonewalling Drosophila stem cell differentiation by epigenetic controls
2007
During Drosophila oogenesis, germline stem cell (GSC) identity is
maintained largely by preventing the expression of factors that promote
differentiation. This is accomplished via the activity of several genes acting
either in the GSC or in its niche. The translational repressors Nanos and
Pumilio act in GSCs to prevent differentiation, probably by inhibiting the
translation of early differentiation factors, whereas niche signals prevent
differentiation by silencing transcription of the differentiation factor Bam.
We have found that the DNA-associated protein Stonewall (Stwl) is also
required for GSC maintenance. stwl is required cell-autonomously;
clones of stwl - germ cells were lost by differentiation,
and ectopic Stwl caused an expansion of GSCs. stwl mutants acted as
Suppressors of variegation, indicating that stwl normally acts in
chromatin-dependent gene repression. In contrast to several previously
described GSC maintenance factors, Stwl probably functions epigenetically to
prevent GSC differentiation. Stwl-dependent transcriptional repression does
not target bam , but rather Stwl represses the expression of many
genes, including those that may be targeted by Nanos and Pumilio translational
inhibition.
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