Deletion producing a frameshift followed by a premature stop codon, resulting in expression of a truncated Amnionless protein lacking the FXNPXF domain required for ligand-independent internalisation, but retaining the three-faced β-helix and the transmembrane domains required in vertebrates for docking of cubilin trimers and their traffic to the membrane (384 wild type amino acids, followed by 6 novel amino acids).