Faculty Bibliography

Nerve growth factor (NGF) receptor mRNA was found to be widely distributed throughout the human central nervous system, with the highest levels in the basal forebrain; this suggests that NGF may function as a retrograde trophic messenger for basal forebrain magnocellular cholinergic nerve cells. The degeneration of the latter constitutes one of the main features of Alzheimer's disease and it may be responsible for some of the cognitive impairment that characterizes the disease. No evidence was obtained for an insufficient synthesis of NGF receptor mRNA in the basal forebrain in Alzheimer's disease, where NGF receptor-like immunoreactivity was confined to neuronal cell bodies. NGF could thus be therapeutically beneficial. It could be expected to induce basal forebrain cholinergic cells to hypertrophy, synthesize more choline acetyltransferase and extend neurites

Recent work has indicated that the trophic protein, nerve growth factor (NGF), is detectable in several brain regions, in addition to its well-known localization to the periphery. In addition, a number of cholinergic populations in the brain respond to NGF by increasing enzymes involved in acetylcholine metabolism. It is well recognized that responsiveness to NGF is dependent on expression of specific receptors; we have recently detected expression by the responsive rat basal forebrain/septal, cholinergic neurons, suggesting that NGF plays a physiologic role in the development of this brain pathway. To define a potential role for NGF in other rat brain regions, we isolated a rat receptor cDNA clone to use as a probe to detect receptor message by sensitive Sl nuclease protection experiments. Our studies indicate that the NGF receptor (NGF-R) gene is expressed by anatomically, functionally and biochemically diverse populations, widely distributed in the rat brain, and is not restricted to the basal forebrain/septal region. We detect NGF receptor message in frontal cortex, hippocampus, caudate, cerebellum and olfactory bulb. Moreover, developmental profiles of steady-state quantities varied differently for each area. Our observations support the contention that NGF regulates multiple brain systems, in addition to forebrain cholinergic pathways

Normal differentiation and malignant transformation of human melanocytes involve a complex series of interactions during which both genetic and environmental factors play roles. At present, the regulation of these processes is poorly understood. We have induced the expression of nerve growth factor (NGF) receptors on cultured human melanocytes with phorbol 12-tetradecanoate 13-acetate and have correlated this event with the appearance of a more differentiated, dendritic morphology. Criteria for NGF receptor expression included protein accumulation and cell-surface immunofluorescent staining with a monoclonal antibody directed against the human receptor and induction of the messenger RNA species as determined by blot-hybridization studies. The presence of the receptor could also be induced by UV irradiation or growth factor deprivation. The NGF receptor is inducible in cultured human melanocytes, and we suggest that NGF may modulate the behavior of this neural crest-derived cell in the skin

The melanoma-associated antigen ME491 is expressed strongly during the early stages of tumor progression. The ME491 gene was molecularly cloned by means of DNA-mediated gene transfer followed by screening a lambda genomic library with human repetitive Alu sequences as a probe. The cloned DNA, after transfection into mouse L-cells, generated a protein with characteristics that were indistinguishable in Western blot analysis from the ME491 antigen expressed by human melanoma cells. Repeat-free subfragments of the cloned DNA were used for further studies. By Northern blot analysis, the subfragments detected a single 1.2-kilobase mRNA in the transformants and various human melanoma cell lines. ME491 complementary DNA clones were then obtained by probing a melanoma complementary DNA library with the genomic subfragments. Nucleotide sequence analysis of the cloned complementary DNA indicated that the ME491 antigen consists of 237 amino acids (Mr 25,475) with four transmembrane regions and three putative N-glycosylation sites. No significant structural homology was observed with other proteins thus far reported. We observed that the amounts of mRNA varied greatly with different melanoma cell lines. Southern blot analysis revealed no amplification or rearrangement of the ME491 gene in the human melanoma cell lines tested, including both high and low expressors of this antigen. The ME491 gene has been mapped to chromosome region 12p12----12q13 by somatic cell hybrid analysis and more narrowly localized to 12q12----12q14 by in situ hybridization

The nerve growth factor (NGF) receptor is an integral membrane protein that is phosphorylated and heavily glycosylated. Determination of the amino acid sequence by molecular cloning indicates that the receptor is a cysteine-rich protein which contains a signal peptide sequence and spans the lipid bilayer with a single transmembrane sequence. A single mRNA of 3.8 kilobases was observed for the receptor, of which 1.5 kilobases is coding sequence. We have used microinjection of receptor RNA in Xenopus laevis oocytes to obtain cell surface expression of the receptor. The presence of NGF receptors in oocytes was verified by radioimmunoassay, specific binding of [125I]NGF, and metabolic labeling followed by immunoprecipitation. The NGF receptor protein was rapidly processed in oocytes and displayed extensive glycosylation. Furthermore, the presence of NGF receptors in oocytes potentiates the ability of progesterone to induce maturation

von Recklinghausen neurofibromatosis (VRNF) is one of the most common inherited disorders affecting the human nervous system. VRNF is transmitted as an autosomal dominant defect with high penetrance but variable expressivity. The disorder is characterized clinically by hyperpigmented patches of skin (cafe au lait macules, axillary freckles) and by multiple tumors of peripheral nerve, spinal nerve roots, and brain (neurofibromas, optic gliomas). These tumors can cause disfigurement, paralysis, blindness, and death. We have determined the chromosomal location of the VRNF gene by genetic linkage analysis using DNA markers. The VRNF gene is genetically linked to the locus encoding nerve growth factor receptor, located on the long arm of chromosome 17 in the region 17q12----17q22. However, crossovers with the VRNF locus suggest that a mutation in the nerve growth factor receptor gene itself is unlikely to be the fundamental defect responsible for the VRNF phenotype

Nerve growth factor (NGF) regulates development and maintenance of function of peripheral sympathetic and sensory neurons. A potential role for the trophic factor in brain has been detected only recently. The ability of a cell to respond to NGF is due, in part, to expression of specific receptors on the cell surface. To study tissue-specific expression of the NGF receptor gene, we have used sensitive cRNA probes for detection of NGF receptor mRNA. Our studies indicate that the receptor gene is selectively and specifically expressed in sympathetic (superior cervical) and sensory (dorsal root) ganglia in the periphery, and by the septum-basal forebrain centrally, in the neonatal rat in vivo. Moreover, examination of tissues from neonatal and adult rats reveals a marked reduction in steady-state NGF receptor mRNA levels in sensory ganglia. In contrast, a 2- to 4-fold increase was observed in the basal forebrain and in the sympathetic ganglia over the same time period. Our observations suggest that NGF receptor mRNA expression is developmentally regulated in specific areas of the nervous system in a differential fashion