VGF Expression Research Articles

Developmental expression of VGF mRNA in the prenatal and postnatal rat

VGF is a developmentally regulated, secretory peptide precursor that is expressed by neurons and neuroendocrine cells and that has its transcription and secretion induced rapidly by neurotrophins and by depolarization. To gain insight into the possible functions and regulation of VGF in vivo, we have characterized the distribution of VGF mRNA in the developing rat nervous system. VGF expression was first detectable at embryonic day 11.5 in the primordia of cranial, sympathetic, and dorsal root ganglia, and its distribution expanded throughout development to include significant expression throughout the brain, spinal cord, and retina of the adult rat. The earliest expression of VGF, therefore, appeared in the peripheral nervous system as developing neurons settled in their designated ganglia. In many regions of the brain, VGF mRNA levels were found to be highest during periods when axonal outgrowth and synaptogenesis predominate. Areas of the central nervous system that contain predominantly dividing cells never displayed any VGF mRNA expression, nor did the vast majority of nonneural tissues.

Comparison of VGF and trk mRNA distributions in the developing and adult rat nervous systems

The vgf gene encodes a neuronal secretory-peptide precursor that is rapidly induced by neurotrophic growth factors and by depolarization in vitro. To gain insight into the possible functions and regulation of VGF in vivo, we characterized the expression of VGF messenger RNA (mRNA) by in situ hybridization, during development and in adult brain, and directly compared it to the distributions of mRNAs encoding neurotrophin receptors TrkA, TrkB, and TrkC. Overlap in VGF and trk mRNA expression exists, and though no trk mRNA was exclusively colocalized with VGF message, the best correlation was found between the distributions of the VGF and trkB kinase mRNAs.

The messenger RNA encoding VGF, a neuronal peptide precursor, is rapidly regulated in the rat central nervous system by neuronal activity, seizure and lesion

The VGF gene encodes a neuronal secretory-peptide precursor that is rapidly induced by neurotrophic growth factors and by depolarization in vitro. VGF expression in the animal peaks during critical periods in the developing peripheral and central nervous systems. To gain insight into the possible functions and regulation of VGF in vivo, we have used in situ hybridization to examine the regulation of VGF messenger RNA by experimental manipulations, and have found it to be regulated in the CNS by paradigms that affect electrical activity and by lesion. Inhibition of retinal electrical activity during the critical period of visual development rapidly repressed VGF messenger RNA in the dorsal lateral geniculate nucleus of the thalamus. In the adult, kainate-induced seizures transiently induced VGF messenger RNA in neurons of the dentate gyrus, hippocampus, and cerebral cortex within hours. Cortical lesion strongly induced VGF messenger RNA in ipsilateral cortex within hours, and strongly repressed expression in ipsilateral striatum. Ten days postlesion there was a delayed induction of VGF messenger RNA in a portion of deafferented striatum where compensatory cortical sprouting has been detected. Expression of the neuronal secretory-peptide precursor VGF is therefore modulated in vivo by monocular deprivation, seizure, and cortical lesion, paradigms which lead to neurotrophin induction, synaptic remodeling and axonal sprouting.

Regulation of thevgf gene in the golden hamster suprachiasmatic nucleus by light and by the circadian clock

By using in situ hybridization in the golden hamster brain, we have found that vgf mRNA levels are induced as a response to light stimulation in the suprachiasmatic nuclei (SCN), the site of the mammalian circadian pacemaker. The induction exhibits delayed kinetics relative to known light-induced immediate early genes: induction of vgf mRNA occurs over a period of 3 to 9 hours after light exposure. Photic induction of vgf expression does not occur in the paraventricular nucleus (PVN) of the hypothalamus, though this nucleus expresses vgf at the mRNA and protein levels. Photic induction of vgf in the SCN occurs only at circadian times when light also causes a phase shift of the circadian system. The irradiance threshold of vgf induction in the SCN closely matches that of the behavioral phase shifting response. In addition, basal expression of vgf in the SCN, but not in the PVN, exhibits a circadian rhythm in constant darkness. The photic induction and circadian rhythm of vgf expression are anatomically separated in the caudal and rostral portions of the SCN, respectively. These results represent the first example of a delayed response to light relative to light-induced immediate early genes at the mRNA level in the SCN.

Expression and polarization of VGF in developing hippocampal neurons

Expression and polarization of VGF in developing hippocampal neurons

Expression and polarization of VGF in developing hippocampal neurons

VGF is an NGF-inducible protein whose expression closely correlates with PC12 cell neurite outgrowth. Immunolocalization of VGF in PC12 cells by electron microscopy revealed labeling of a subpopulation of large dense core vesicles. To determine whether VGF expression may be involved in neural and axonal differentiation, we examined VGF immunoreactivity in developing cultured hippocampal neurons. Most VGF appeared to be in vesicles which were present in neurons from the earliest developmental stages and were particularly abundant in a small number of neurons, most of which were GABAergic. VGF became restricted to axons after dendrites had begun to mature, a stage more closely associated with synaptogenesis than axonal polarization. Colocalization studies suggest that VGF-containing and synaptophysin-containing vesicles are distinct and differentially distributed.

The "VGF" protein in rat adenohypophysis: sex differences and changes during the estrous cycle and after gonadectomy

Gene expression and cell localization of the neuroendocrine protein VGF were studied in the rat anterior pituitary. In females, four antisera against nonoverlapping regions of VGF immunostained a small number of lactotropes and many gonadotropes. In the latter cells, VGF immunoreactivity was localized to a subpopulation of secretory granules. Distinct changes were seen after estrus, with a significant increase in VGF messenger RNA (whole pituitary), whereas VGF immunostaining was strikingly reduced in gonadotropes and somewhat more abundant in lactotropes. In male rats, gene expression was low, and immunoreactivity was restricted to a few lactotropes. After castration or ovariectomy, VGF messenger RNA was high, and VGF immunoreactivity was abundant in gonadotropes. Selective localization and cyclic modulation suggest involvement of the VGF gene product(s) in pituitary gonadotrope and/or lactotrope function.

A developmentally regulated nerve growth factor-induced gene, VGF, is expressed in geniculocortical afferents during synaptogenesis.

The expression of the nerve growth factor-inducible gene VGF has been examined by in situ hybridization. Western blot and immunohistochemical studies in the developing and adult rat central nervous system, with particular emphasis on the visual system. Both the messenger RNA and the protein are particularly abundant in the developing dorsal lateral geniculate nucleus, appearing, respectively, at embryonal day 16 and 18. After its onset at E16, VGF messenger RNA expression increases progressively in the dorsal lateral geniculate nucleus and remains high during the first two post-natal weeks; afterwards, it gradually decreases and, at the offset of the plasticity period, it reaches very low levels maintained in adulthood. A similar time course has been observed for VGF protein in the dorsal lateral geniculate nucleus area, by semi-quantitative Western blots. In addition to the presence of the protein in the geniculate neurons, a strong, transient immunoreactivity has been found at the embryonic cortical subplate at E18, reflecting the presence of the antigen in axonal terminals originating from thalamic neurons. Interestingly, we found that the blockade of afferent electrical activity by intraocular injection of tetrodotoxin strongly reduces the level of VGF messenger RNA in the dorsal lateral geniculate nucleus. Although the function of the VGF protein is not known, it had been previously proposed that VGF could be a precursor for neuropeptide/s. The spatiotemporal expression of VGF, together with the observation of a regulation by electrical activity, suggest that this protein may be relevant in the process of synaptogenesis and/or synaptic stabilization in the developing geniculocortical connections.

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.

Recombinant human bone morphogenetic protein 2B stimulates PC12 cell differentiation: potentiation and binding to type IV collagen.

Bone morphogenetic protein 2B (BMP 2B, also known as BMP 4) induces cartilage and bone morphogenesis in ectopic extraskeletal sites. BMP 2B is one of several bone morphogenetic proteins which along with activins and inhibins are members of the transforming growth factor-beta (TGF-beta) family. Both BMP 2B and activin A, but not TGF-beta 1, induce rat pheochromocytoma PC12 neuronal cell differentiation and expression of VGF, a nervous system-specific mRNA. PC12 cells exhibited approximately 2,500 receptors per cell for BMP 2B with an apparent dissociation constant of 19 pM. Extracellular matrix components, including fibronectin, laminin, and collagen type IV potentiated the activity of BMP and activin A, with the latter being the most active. Direct experiments demonstrated that radioiodinated BMP 2B bound to collagen type IV better than to either laminin or fibronectin. These data demonstrate a common neurotrophic activity of both BMP 2B and activin A, and suggest that these regulatory molecules alone and in conjunction with extracellular matrix components may play a role in both the development and repair of nervous tissue.

Expression in murine and human neuroblastoma cell lines of VGF, a tissue specific protein

Screening by different means has demonstrated the presence, in human and murine neuroblastoma cell lines, of VGF, a gene product identified in a limited number of neuronal and endocrine cells. Indirect immunofluorescence and Western and Northern blot analyses have shown the presence of this protein in some of the tested lines, confirming that VGF is not an ubiquitous molecule. Further studies, using human SK-N-BE and murine N18TG2 lines, showed that VGF expression is upregulated during differentiation, suggesting that various species, including man, express VGF and regulate it in a similar manner. The subcellular localization of the protein, which is associated with vesicles, its electrophoretic molecular profile and its specific release under different conditions are all consistent with results reported in other cells. Neuroblastomas are thus added to the class of VGF-positive cells and provide a new in vitro model for investigation of the structural and functional properties of this protein.

Regulatory elements in the promoter region of vgf, a nerve growth factor-inducible gene.

vgf, a gene coding for a protein secreted through the regulated pathway, is rapidly up-modulated by nerve growth factor in PC12 cells and is expressed in vivo only in cell subpopulations of neuronal and endocrine origin. Here we demonstrate the following: (i) the nerve growth factor-dependent induction of vgf mRNA occurs at the transcriptional level and requires ongoing protein synthesis, (ii) lack of vgf expression in the nonneuronal cell line HTC is in part mediated by the presence of a repressor, (iii) a 110-base-pair sequence in the vgf promoter region contains positive and negative regulatory elements that partially account for its regulated expression, and (iv) a 47-base-pair oligonucleotide within this sequence specifically binds nuclear proteins that differ between vgf-expressing and non-expressing cells.

Hypothalamic expression of a novel gene product, VGF: immunocytochemical analysis

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 PC12 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. Immunostaining of serial 1 micron 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 present in some regions of the hypothalamus and in the external and internal zones of the median eminence. Immunoreactivity is absent from the intermediate lobe of the hypophysis. In neonatal rats strong VGF immunoreactivity is found throughout the SCN at postnatal day 4 but not in the adjacent hypothalamus. VGF immunoreactivity is also seen in other areas of the brain in neonatal rats, including the lateral geniculate nucleus; while the staining in the dorsal lateral geniculate disappears in the adult, that in the intergeniculate leaflet, a visual center which projects to the SCN, remains.(ABSTRACT TRUNCATED AT 400 WORDS)