Mechanism of SB431542 in inhibiting mouse embryonic stem cell differentiation.

SB431542 (SB) is an established small molecular inhibitor that specifically binds to the ATP binding domains of the activin receptor-like kinase receptors, ALK5, ALK4 and ALK7, and thus specifically inhibits Smad2/3 activation and blocks TGF-β signal transduction. SB maintains the undifferentiated state of mouse embryonic stem cells. However, the way of SB in maintaining the undifferentiated state of mouse embryonic stem cells remains unclear. Considering that SB could not maintain embryonic stem cells pluripotency when leukemia inhibitory factor was withdrawn, we sought to identify the mechanism of SB on pluripotent maintenance. Transcripts regulated by SB, including message RNAs and small non-coding RNAs were examined through microarray and deep-sequence experiments. After examination, Western blot analysis, and quantitative real-time PCR verification, we found that SB regulated the transcript expressions related to self-renewal and differentiation. SB mainly functioned by inhibiting differentiation. The key pluripotent factors expression were not significantly affected by SB, and intrinsic differentiation-related transcripts including fibroblast growth factor family members, were significantly down-regulated by SB. Moreover, SB could partially inhibit the retinoic acid response to neuronal differentiation of mouse embryonic stem cells.