HOMEOBOX GENE-PRODUCT NKX-6.1 IMMUNOREACTIVITY IN NUCLEI OF ENDOCRINE-CELLS OF RAT AND MOUSE STOMACH

The homeobox gene product Nkx 6.1 is of unknown function but is expres sed in the pancreas and the antropyloric mucosa of the stomach. In the adult pancreas, Nkx 6.1 possesses an insulin cell-restricted distribu tion, whereas its localization in the stomach is unknown. We now show that the vast majority of serotonin-producing enterochromaffin cells o f the antropyloric mucosa contain Nkx 6.1-immunoreactive nuclei. In ad dition, a subpopulation of cells co-storing serotonin and gastrin disp lay Nkx 6.1-positive nuclei. Such cells have been postulated to repres ent precursors of mature gastrin and serotonin cells. The nuclei of th e co-storing cells have previously also been found to be positive for another homeodomain protein, Pdx-1. Pdx-1-deficient animals were there fore investigated and were found to be devoid of Nkx 6.1-positive nucl ei. Our data show that Pdx-1 is needed for Nkx 6.1 expression and sugg est a role for Nkx 6.1 in the maturation of gastrin-and serotonin-posi tive precursor cells.