Agrin is a large chimeric proteoglycan, a heparan sulfate and chondroitin proteoglycan, whose best-characterised role is in the development of the neuromuscular junction during embryogenesis

Agrin was originally found in the electric organ of Tarpedo california and in the basal lamina at the neuromuscular junction as a protein that directs the aggregation of acetylcholine receptors (AChR) and acetylcholinesterase (AChE) at synaptic