Recently, IA-2, one of Ihs major diabetic autoantigens, and PTP35 cDNA were independently isolated by subtraction cloning using insulinoma cells and a polymerase chain reaction (PCR)-based search for conserved sequences using NIH3T3 fibroblast cell line, respectively. By Southern blot analysis and nucleotide sequence determination of reverse transcription PCR products, we showed that IA-2 and PTP35 are identical and exist as a single gene in a mouse genome. The expression of IA-2/PTP35 messages was detected by northern blot analysis in MIN6N8 cells, an insulinoma cell line derived from non-obese diabetic mice, but its expression level was not affected by the ambient glucose level, phorbol-12-myristate 13-acetate or tumour necrosis factor-alpha. We also generated polyclonal antibodies to murine IA-2/PTP35 by immunization with recombinant proteins. Subsequent immunohistochemical analysis using those polyclonal antibodies disclosed that IA-2/PTP35 is strongly expressed in mouse neuroendocrine tissues such as pancreatic islets and the hypothalamus-pituitary gland. These results suggest that IA-2/PTP35 functions primarily in neuroendocrine tissues. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.