Practice question

Stem maintenance integrates canonical pathways coordinating self-renewal versus fate choice. Wnt beta-catenin drives intestinal crypt and hematopoietic self-renewal via TCF4 target Myc, JAK-STAT activated by LIF maintains mouse embryonic stem pluripotency and Drosophila male germline via Upd ligand and Stat92E, Hedgehog via Gli supports neural and hair follicle proliferation. Complement cascade constitutes innate immune effector activating C3a C5a opsonization, membrane attack complex and inflammation leading to pathogen clearance not intrinsic stem regulation. While inflammation indirectly modulates niche, complement components are not core fate determinants like Wnt, Hedgehog or JAK-STAT pathways.