Cloning of cDNAs from a mammalian expression library by a direct selection-amplification method

A sensitive method was devised for cloning cDNAs from a mammalian expression library based on single-cell detection and selection of transfected cells. The method is applicable for cloning cell-surface or cytoplasmic proteins for which a detection assay, such as immunofluorescence or immunohistochemical reactivity, exists. The widely used eukaryotic expression vector cdm8 is utilized, and the method is demonstrated using the gene for C-CAM, a liver glycoprotein adhesion molecule. After transfection, cells are plated out on a collagen gel substrate to allow retrieval of selected cells. Simultaneous fixation and permeabilization with acetone permits immunological and histochemical detection of cell-surface and cytoplasmic proteins without loss of plasmid vector. Inserts of interest are recovered by PCR with vector primers.