Nucleic acids encoding the neurotrophic protein known as pigment epithelium-derived factor (PEDF), a truncated version of PEDF referred to as rPEDF, and equivalent proteins, vectors comprising such nucleic acids, host cells into which such vectors have been introduced, recombinant methods for producing PEDF, rPEDF, and equivalent proteins, the rPEDF protein and equivalent proteins of rPEDF and PEDF-BP, -BX and BA, and the PEDF protein produced by recombinant methods. Effects and uses of these variants on 1) neuronal differentiation (neurotrophic effect) 2) neuron survival (neuronotrophic effect) and 3) glial inhibition (gliastatic effect) are described.