PTPRN and type 1 diabetes mellitus: Interestingly, many autoantigens targeted by the immune response in T1D are expressed by different nervous and neuroendocrine tissues, such as GAD65, glutamic acid decarboxylase 67, islet cell antigen 512 (also referred to as IA-2), phogrin (also referred to as IA-2–β), islet cell antigen 69, or chromogranin A (39).