The pancreatic homeodomain transcription factor IDX1/IPF1 is expressed in neural cells during brain development

Expression of the homeodomain transcription factor IDX1/IPF1 has been shown to be restricted to cells in the developing foregut that form the pancreatic primordium. In the adult, IDX1/IPF1 is expressed in the duodenum and pancreatic islets. The IDX1/IPF1 gene is required for pancreatic development, and in the human, heterozygous mutations have been linked to diabetes mellitus. In the present communication, we report that IDX1/IPF1 is expressed in discrete cells of the rat central nervous system during embryonic development. Using RT-PCR, IDX1/IPF1 mRNA was detected in neural precursor RC2.E10 cells, as well as in both forebrain and hindbrain of developing rats at embryonic day 15 (E15). The presence of IDX1/IPF1 protein was confirmed by Western immunoblotting. Immunohistochemical analyses of sagittal sections of E15 rats demonstrated the presence of scattered IDX1/IPF1-immunopositive cells in the forebrain. Finally, electrophoretic mobility shift assays using nuclear extracts from neural cells revealed the presence of IDX1/IPF1 bound to a putative homeodomain protein DNA-binding site present in the promoter of the glial fibrillary acidic protein gene. Our results suggest that IDX1/IPF1 may have previously unsuspected extrapancreatic functions during development of neural cells in the central nervous system.