Described are methods for identifying, selecting, and obtaining mammalian cells capable of producing proteinaceous molecules having predetermined post-translational modifications, wherein the post-translational modifications are brought about by the mammalian cell in which the proteinaceous molecule is expressed. Preferably, the predetermined post-translational modifications include glycosylation. Also described are methods for obtaining and producing proteinaceous molecules, using mammalian cells obtainable by a method of the present invention. Preferably, the proteinaceous molecules include erythropoietin (EPO), since EPO's effect depends heavily on its glycosylation pattern. Mammalian cells that have been obtained on the basis of their ability to produce proteins and/or post-translational modifications that are indicative for a predetermined post-translational modification that is desired are also provided. Preferably, the mammalian cells have neural characteristics and properties, such that significant amounts of recombinant proteins can be produced that harbor “neural- or brain-type” properties.