CREB1 and bipolar disorder: However, further studies are needed to establish whether reduced expression of BDNF is sufficient to produce the altered expression of Spry2 in the DLPFC of subjects with schizophrenia or bipolar disorder since other growth factors, such EGF and FGF are also known to regulate Spry2 expression, at least in in vitro conditions [31]–[33], and the transcription factors CREB and Sp1 are involved in other growth factor signaling pathways [34]–[35].