VGF expression in the brain.

VGF is a neuronal polypeptide first identified as a cDNA clone in a gene library from nerve growth factor-stimulated PC12 cells. In the present paper, the expression of VGF is examined for the first time throughout the adult rat central nervous system with immunocytochemistry and Northern blot analysis. VGF RNA was found in all brain regions studied, including hypothalamus, hippocampus, cerebellum, olfactory bulb, and cortex. In contrast to the relatively strong immunostaining of hypothalamic neurons, the level of VGF RNA expression in the hypothalamus was relatively low in comparison with other brain regions. With the aid of antisera raised against bacterially produced recombinant proteins containing parts of the VGF sequence, immunoreactive neurons were detected throughout the brain, including regions of the olfactory tubercle, caudate-putamen, thalamus, cortex, amygdala, hypothalamus, midbrain, and hippocampus. VGF-immunoreactive neurons did not contain detectable amounts of nerve growth factor receptor; other neurons that showed nerve growth factor receptor immunoreactivity expressed no VGF immunoreactivity. The lack of colocalization of VGF and nerve growth factor receptor suggests that, unlike expression in PC12 cells, VGF expression in neurons from the central nervous system does not require nerve growth factor stimulation. Within the hippocampus, the location of VGF-immunoreactive cells was suggestive of inhibitory interneurons. VGF-immunoreactive axons and terminals were found throughout the brain. These observations extend our earlier work on VGF expression in the hypothalamus to other regions of the brain and support the conclusion that although VGF expression is only detected in subsets of neurons in each brain region, these subsets are widely distributed throughout the central nervous system.