The scaffolding function of LSD1/KDM1A reinforces a negative feedback loop to repress stem cell gene expression during primitive hematopoiesis.

Lsd1/Kdm1a functions both as a histone demethylase enzyme and as a scaffold for assembling chromatin modifier and transcription factor complexes to regulate gene expression. The relative contributions of Lsd1's demethylase and scaffolding functions during embryogenesis are not known. Here, we analyze two independent zebrafish mutant lines and show Lsd1 is required to repress primitive hematopoietic stem cell gene expression.