Faculty Bibliography

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

Alleles for the single human nerve growth factor receptor gene (NGFR) on chromosome 17q can be distinguished by two polymorphic restriction sites for XmnI and one for HincII. The combined information content for haplotypes is quite high, making the NGFR locus an excellent genetic marker. Two of these polymorphisms were used to follow the inheritance of NGFR alleles in families with two or more members affected with familial dysautonomia. This rare disease is inherited in an autosomal recessive mode in the Ashkenazic Jewish population. Affected individuals show a severe depletion of NGF-dependent nerve populations from birth. Linkage analysis excluded a role for NGFR in this disease with odds of greater than 10(6):1 against the dysautonomia gene being within 1 centiMorgan of the mutation. In a previous study the gene for the beta subunit of NGF (NGFB) was also excluded in this disease. A possible role for other genes involved in NGF action or those coding for other developmentally determining neuronal factors is indicated

Nerve growth factor (NGF) and its receptor are important in the development of cells derived from the neural crest. Mouse L cell transformants have been generated that stably express the human NGF receptor gene transfer with total human DNA. Affinity cross-linking, metabolic labeling and immunoprecipitation, and equilibrium binding with 125I-labeled NGF revealed that this NGF receptor had the same size and binding characteristics as the receptor from human melanoma cells and rat PC12 cells. The sequences encoding the NGF receptor were molecularly cloned using the human Alu repetitive sequence as a probe. A cosmid clone that contained the human NGF receptor gene allowed efficient transfection and expression of the receptor

We have previously shown that insulin and the insulin-like growth factors share some important neurotrophic properties with nerve growth factor (NGF), including the capacity to enhance neurite formation. In this study, we have examined the effects of these neuritogenic agents on the expression of genes coding for important cytoskeletal proteins of axons and dendrites. Insulin specifically and coordinately increased the levels of alpha- and beta-tubulin mRNAs in human neuroblastoma SH-SY5Y cells. The dose-response curves for these increases were very similar to that for enhancement of neurite formation. Tubulin transcripts reached a transient maximum in approximately 1 day, suggesting that higher levels are important during initiation of neurites and that high levels are not required to sustain neurites once formed. Insulin-like growth factor II shared with insulin the capacity to substantially increase tubulin mRNA levels. NGF had but a small effect. Complementary mechanisms for these neurotrophic agents are suggested, because other studies show NGF and insulin can synergistically potentiate neurite formation. None of the factors altered the levels of actin mRNA. Thus, neurite formation does not seem to require a coordinate increase in actin and tubulin transcripts in SH-SY5Y cells

We have introduced a hybrid mouse-human beta-globin gene as well as the intact human beta-globin gene into murine erythroleukemia (MEL) cells and have demonstrated that these genes are appropriately regulated during differentiation of the MEL cell in culture. The addition of chemical inducers to cotransformed cells results in a 5 to 50 fold increase in the level of mRNA transcribed from the exogenous globin gene. S1 nuclease and primer extension analyses demonstrate that these mRNAs initiate and terminate correctly. Nuclear transcription experiments indicate that induction of hybrid mRNA results at least in part from the increase in the rate of globin gene transcription. Furthermore, the induction appears to be specific for globin genes within an erythroid cell. These results permit the study of expression of the globin gene during erythroid differentiation and suggest that the specific induction of the globin gene is an inherent property of DNA sequences within or flanking the beta-globin genes. Moreover, the fact that the human and hybrid globin genes are both inducible in MEL cells suggests that these regulatory sequences are conserved between mouse and human cells