Hypothalamic Expression of a lmmunocytochemical Analysis Novel Product, VGF:

VGF is the designation for a new 712 amino acid protein, regulated by nerve growth factor (NGF) in PC12 cells, that has not been previously described in the CNS. Northern blot analysis with a nick-translated VGF cDNA probe revealed a single band of mRNA in the brain with a molecular weight identical to that found in PC1 2 cells. The current paper presents a series of immunocytochemical studies of VGF expression with a focus on the hypothalamus. Two different antisera were raised against nonoverlapping amino acid sequences of a bacterial-expressed protein from the VGF gene cloned from PC12 cells. VGF immunoreactivity is strongly expressed in the rat suprachiasmatic nucleus (SCN), particularly in the dorsomedial part of the nucleus. The administration of colchicine to block axonal transport facilitates detection of the VGF immunoreactivity also in the ventrolateral suprachiasmatic nucleus. This protein appears to be the first one of limited neuronal distribution which is found in both dorsomedial SCN and ventrolateral SCN. lmmunostaining of serial 1 Mm SCN sections reveals co-localization of VGF in cells which also contain vasopressin or vasoactive intestinal polypeptide. Weaker immunoreactivity is also found in the magnocellular paraventricular and supraoptic nuclei, where the VGF immunoreactivity co-localizes with oxytocin or vasopressin. Mutant Brattleboro rats which do not express vasopressin showed strong VGF immunoreactivity both in the dorsomedial SCN and in cells of the magnocellular neuronal systems, including cells which normally express vasopressin. When axonal transport of the protein is blocked by colchicine, VGF-immunoreactive cells in the hypothalamic arcuate, parvocellular paraventricular, and tuberomammillary nuclei can also be detected, in addition to weakly immunoreactive scattered cells in the hippocampus, amygdala, thalamus, and cortex. VGF immunoreactivity is strong in the axonal projections of SCN and weak in the axons of the paraventricular and supraoptic nuclei. With ultrastructural studies, VGF immunoreactivity is found in presynaptic boutons in the SCN and in axons in the neurohypophysis. Weak axonal staining is