Follistatin-like 1 attenuates differentiation and survival of erythroid cells through Smad2/3 signaling.

Hematopoiesis is a complex process tightly controlled by sets of transcription factors in a context-dependent and stage-specific manner. Smad2/3 transcription factor plays a central role in differentiation and survival of erythroid cells. Here we report that follistatin-like 1 (FSTL1) treatment impairs hemin-induced erythroid differentiation and cell survival. FSTL1 differentially regulates transforming growth factor beta (TGF-β) and bone morphogenetic protein (BMP) signaling. Blockade of Smad2/3 signaling with the ALK5/type I TGF-βR kinase inhibitor, SB-525334, was efficacious for rescue of erythroid differentiation blockage and apoptosis. Reversely, activation of Smad1/5/8 signaling with BMP4 cannot rescue FSTL1-mediated erythroid differentiation blockage and apoptosis. Collectively, these data provide mechanistic insight into the regulation of erythropoiesis by FSTL1 signaling and lay a foundation for exploring FSTL1 signaling as a therapeutic target for anemia.