The present invention concerns improved methods and compositions for producing a Neublastin polypeptide as well as local delivery of Neublastin to specific regions of the nervous system including the central nervous system and the eye for example by gene therapy. The invention also concerns Neublastin expression constructs which do not encode a pro-region of a Neublastin polypeptide, which expression construct result in increased secretion of bioactive Neublastin. The invention includes the delivery of Neublastin from transduced or transfected cells encapsulated into a macrocapsule with a semipermeable membrane. The invention further concerns mammalian cells capable of producing Neublastin in increased amounts.