GMFB and schizophrenia: In conclusion, there is a great potential for BDNF, GMF-β, and the 115-kDa isoform of RAB3GAP1 proteins to act as possible biomarkers of schizophrenia, and they may even differentiate early stages (e.g. BDNF) from later stages (e.g. GMF-β) of the disease.