An arm promoter drives expression of a cDNA that encodes the stan-PA protein isoform, in which sequence encoding the C-terminal three amino acids (the PDZ-binding motif) has been deleted. An EGFP tag has been introduced in frame after residue Q355 (this is 5 residues downstream of the predicted PRO cleavage site and 7 residues upstream of the start of the first cadherin repeat).