Chavan, A.; Isenhart, R.; Nguyen, S. C.; Kotb, N.; Harke, J.; Sintsova, A.; Ulukaya, G.; Uliana, F.; Ashiono, C.; Kutay, U.; Pegoraro, G.; Rangan, P.; Joyce, E. F.; Jagannathan, M.

The association of genomic loci to the nuclear periphery is proposed to facilitate cell-type specific gene repression and influence cell fate decisions. However, the interplay between gene position and expression remains incompletely understood, in part because the proteins that position genomic loci at the nuclear periphery remain unidentified. Here, we used an Oligopaint-based HiDRO screen targeting ~1000 genes to discover novel regulators of nuclear architecture in Drosophila cells. We identified the heterochromatin-associated protein, Stonewall (Stwl), as a factor promoting perinuclear chromatin positioning. In female germline stem cells (GSCs), Stwl binds and positions chromatin loci, including GSC differentiation genes, at the nuclear periphery. Strikingly, Stwl-dependent perinuclear positioning is associated with transcriptional repression, highlighting a likely mechanism for the known role of Stwl in GSC maintenance and ovary homeostasis. Thus, our study identifies perinuclear anchors in Drosophila and demonstrates the importance of gene repression at the nuclear periphery for cell fate.