Anterior enhancement of neural stem cell program by PRC2–Hox.

EFs generate NBs and drive NB and daughter proliferation. In the nerve cord, EF activity is counteracted by Hox homeotic genes, forming a gradient of EF expression, NB proliferation, and the Type I->0 daughter proliferation switch. This results in a gradient of lineage size along the nerve cord. In the brain, PRC2 prevents Hox expression, allowing for further elevation of EF expression and thereby extended NB proliferation and an absence of the Type I->0 daughter proliferation switch. This results in even larger lineages in the brain (see text for details). Antp, Antennapedia; Ase, Asense; BX-C, Bithorax Complex; Cas, Castor; CycE, Cyclin E; Dap, Dacapo; EF, Early Factor; Grh, Grainy head; Hb, Hunchback; Hox, Homeobox; Kr, Kruppel; NB, neuroblast; Pdm, POU domain; PRC2, Polycomb Repressor Complex 2; SoxN, SoxNeuro; St, Stage; Stg, String; Wor, Worniou.