Integrated physical, genetic, and genic map covering 3 Mb around the human NGF gene (NGFB) at 1p13

The nerve growth factor and its receptors in airway inflammatory diseases

The nerve growth factor (NGF) belongs to the neurotrophin family and induces its effects through activation of 2 distinct receptor types: the tropomyosin-related kinase A (TrkA) receptor, carrying an intrinsic tyrosine kinase activity in its intracellular domain, and the receptor p75 for neurotrophins (p75NTR), belonging to the death receptor family. Through activation of its TrkA receptor, NGF activates signalling pathways, including phospholipase Cgamma (PLCgamma), phosphatidyl-inositol 3-kinase (PI3K), the small G protein Ras, and mitogen-activated protein kinases (MAPK). Through its p75NTR receptor, NGF activates proapoptotic signalling pathways including the MAPK c-Jun N-terminal kinase (JNK), ceramides, and the small G protein Rac, but also activates pathways promoting cell survival through the transcription factor nuclear factor-kappaB (NF-kappaB). NGF was first described by Rita Levi-Montalcini and collaborators as an important factor involved in nerve differentiation and survival. Another role for NGF has since been established in inflammation, in particular of the airways, with increased NGF levels in chronic inflammatory diseases. In this review, we will first describe NGF structure and synthesis and NGF receptors and their signalling pathways. We will then provide information about NGF in the airways, describing its expression and regulation, as well as pointing out its potential role in inflammation, hyperresponsiveness, and remodelling process observed in airway inflammatory diseases, in particular in asthma.

Alternative usage of 5′ exons in the chicken nerve growth factor gene: refined characterization of a weakly expressed gene

Nerve growth factor (NGF) is the prototype member of the neurotrophin family. Identification of transcript structures and promoter regions is described here in view of clarifying the molecular basis of chicken NGF gene regulation. Chicken NGF complementary DNA (cDNA) was amplified from heart and brain mRNA using the single-strand ligation to cDNA (SLIC) procedure. Several cloning and sequencing rounds were necessary to elucidate the diversity of NGF transcripts. The chicken NGF gene was shown to possess, in addition to its unique 3' coding exon, five 5' exons grouped into two clusters that have been entirely sequenced. The first cluster encompasses three leader exons (1a, 1b and 1c) and is separated from the second cluster by a approximately 15 kilobases (kb) intronic sequence. "Exon walking" based on reverse transcription-polymerase chain reaction (RT-PCR) allowed to ascertain the length of the three leader exons. The second cluster contains exons 2 and 3, separated from each other by a approximately 2.4 kb intron, and lies approximately 0.5 kb upstream from coding exon 4. Combination of several mechanisms, such as differential usage of leader and internal exons, alternative transcription start inside exon 1b, second donor and acceptor sites in exon 1c and 4, respectively, leads to the production of at least 21 different transcripts. This remarkable diversity may represent a common feature largely underestimated for other weakly expressed genes. Preliminary RT-PCR expression study in a panel of chicken tissues shows that transcripts containing exon 1b are present in most tissues tested. Transcripts containing exon 1a are represented mainly in heart and reproductive organs, whereas transcripts containing exon 1c are mostly represented in peripheral organs other than heart. Complementary data are published as a Web supplement available at.