The protein was subsequently purified from the extract of the synapse rich Torpedo electric organ and, based on the observed aggregating activity, was named ����agrin����, coming from Greek ����ageirein���� which means ����to assemble����. Further studies revealed that agrin is synthesized by motor neurons that release it into the synaptic cleft where it stably integrates into the synaptic basal lamina, a specialized thin layer of the extracellular matrix. Based on these Flufenamic acid findings, McMahan proposed the ��agrin hypothesis�� which states that agrin is a nerve-derived synaptic organizing molecule. Agrin has been cloned from several vertebrate species including rat, chick, marine ray and man. All described agrin gene orthologues encode a large protein of more than 2000 amino acids with an approximate molecular weight of 225 kDa. Additional O-linked glycosylation by heparan and chondroitin sulphate glycosaminoglycan chains, together with N-linked carbohydrates, raise the molecular weight up to 400�C 600 kDa. The domain architecture of agrin is characterized by several repeated structural motifs which share homology with follistatin, laminin epidermal growth factor and laminin globular domains. To localize the agrin protein, the worms were co-stained with the monoclonal antibody pool against C. Halcinonide elegans agrin and with polyclonal anti-rim antibody, recognizing a pre-synaptic marker prominent in the nerve ring. The major site of agrin expression was around the pharynx and the staining was particularly enriched in the anterior part. The posterior bulb was labeled more weakly correlating with the fainter GFP reporter expression in the posterior part. Polyclonal antiserum staining resulted in the same staining pattern in wild type worms of different developmental stages. Young larvae generally showed stronger agrin staining compared to young adults. Pharyngeal staining was absent in all three agrin mutant strains, which is an additional confirmation for their lack of agrin expression. No staining could be observed in body wall muscles, in the synapses along the ventral and dorsal nerve cords, in the gonad and in the posterior gut cells.