Protein-Tyrosine Phosphatase Receptor-Type IA-2(beta) (PTP IA-2(beta)), alternately known as PTPRN2 or Phogrin, localizes in dense-core secretory vesicles of pancreas islet cells and influences insulin secretion. The PTP IA-2(beta) precursor is an autoantigen that contributes to insulin-dependent diabetes mellitus (IDDM). The autoantigenic epitopes of PTP IA-2(beta) appear within the cytoplasmic domain of this transmembrane protein. PTP IA-2(beta) is present at high levels in brain and pancreas with lower levels in trachea, prostate, stomach and spinal cord. The human PTPRN2 gene maps to chromosome 7q36. Northern blot analysis showed that PTPRN2 was expressed as 5.5- and 3.7-kb transcripts primarily in human brain and pancreas. Three alternative transcript splice variants of this gene encode distinct proteins.