Figure 3. Non-neutral competition in the Drosophila testis niche.
(a) In a wild type testis stem cell niche (left image), a one-to-two ratio of GSCs (gray) to CySCs (blue) is maintained around the hub (green). Following global ectopic Bam expression (right image), GSCs differentiate into spermatogonia (gray clusters), leaving CySCs (blue) completely surrounding the hub. Following restoration of normal Bam expression, spermatogonial cysts dedifferentiate into GSCs which outcompete CySCs, restoring the wild type GSC to CySC ratio around the hub (left image). (b) The wild type ratio of GSCs to CySCs (left image) is also disrupted when a Socs36E mutation is induced in the CySCs. The CySCs become more adherent and outcompete neighboring GSCs for space around the hub, decreasing the GSC to CySC ratio (right image).