PTPRN and type 1 diabetes mellitus: Phogrin (IA-2β or PTPRN2) and IA-2 (PTPRN or ICA512), autoantigens in insulin-dependent diabetes, are type 1 transmembrane proteins belonging to the IA-2 family of protein-tyrosine phosphatase (PTP) [1,2,3,4,5,6].