Regional expression of a gene encoding a neuron-specific Na+-dependent inorganic phosphate cotransporter (DNPI) in the rat forebrain

We have analyzed expression of a gene encoding a brain-specific Na+-depende nt inorganic phosphate cotransporter (DNPI), which was recently cloned from human brain, in rat forebrain using in situ hybridization. The expression of DNPI mRNA showed a widespread but highly heterogeneous pattern of distri bution in the forebrain, where hybridization signals were observed in neuro ns but not in any other types of cells. Neurons expressing the mRNA were fa r more numerous in the diencephalon than in the telencephalon. In the thala mus, a number of neurons with high levels of signals were localized to all nuclei of the dorsal thalamus, habenular nuclei and subthalamic nucleus, bu t not the reticular nucleus and zona incerta. Moderate signal levels were s een in many neurons throughout the hypothalamus, particularly the ventromed ial, paraventricular, supraoptic and arcuate nuclei, lateral hypothalamic a rea and mammillary complex. In contrast, expression of DNPI mRNA in the tel encephalon was generally at a low level and occurred locally in some restri cted regions within the neocortex, retrosplenial cortex, piriform cortex, o lfactory regions, hippocampal formation and medial amygdaloid nucleus. The present results suggest that DNPI functions in heterogeneous neuron populat ions as a neuron-specific Nac-dependent inorganic phosphate cotransport sys tem predominantly expressed in the diencephalon of the rat. (C) 2000 Elsevi er Science B.V. All rights reserved.