Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The authors report the results of a genetic analysis performed in 34 neurofibromatosis type 1 (NF1) Italian families using five loci tightly linked to NF1: D17S33, D17S82, D17S83, D17S37, and D17S36. A two-point linkage analysis was performed with the LINKAGE and the CRI-MAP programs. The map of the region was constructed using the MAP90 program. Data from the present study lend further support to evidence that all NF1 mutations are allelic and that the NF1 locus resides in the proximal region of chromosome 17q. Close linkage of NF1 to all the markers was found. Two of them, namely D17S82 and D17S83, showed the highest linkage with a value of 0 recombination frequency and lod scores of 3.77 and 4.02, respectively. The best map found is D17S33-D17S82-NF1-D17S83-D17S37-D17S36+ ++. The authors stress that knowledge of precise order is essential; if D17S82 and D17S83 are proved to flank the NF1 gene, they allow an acceptable presymptomatic diagnosis in informative families.
 ...
PMID:Linkage analysis of neurofibromatosis type 1. Study of a homogeneous North Italian population with five DNA markers of chromosome 17. 167 20

In addition to reporting, in accompanying papers, their individual analyses of mapping the neurofibromatosis type 1 (NF1) gene on chromosome 17, members of the International Consortium for NF1 Linkage contributed their data for our joint analysis to determine the exact sequence of flanking markers and to obtain precise estimates and confidence limits of the recombination fractions for the closest markers, in anticipation of clinical use. With specimens from 142 families and more than 700 affected persons, eight teams used 31 markers in the pericentric region of chromosome 17 to perform 13,838 genotypings. With the combined data, we used the computer program CRI-MAP to build the most likely sequence of loci by sequentially adding single loci to a fixed pair of loci and separately calculating the likelihood of all permutations of four consecutive loci. The best order is pter-pA10-41-EW301-centromere (p17H8)-pHHH202-NF1-EW206-EW207-EW203++ +-CRI-L581-CRI-L946-HOX2-NGFR-qter. The total genetic distance from pA10-41 to NGFR is 26 cM in males and 56 cM in females, and the overall difference in sex-specific maps is statistically significant (P = .006). The upper 99% confidence limits of the recombination fraction of the closest proximal marker, pHHH202, is 4%, and that for the closest distal marker, EW206, is 9%. These limits should decrease with the use of additional probes and the further evaluation of DNA from the six persons showing multiple recombinations within short genetic distances. Clinical application is technically feasible with currently available markers, although its appropriate use for prenatal and presymptomatic diagnosis requires further discussion and evaluation.
 ...
PMID:Multipoint linkage analysis in neurofibromatosis type I: an international collaboration. 249 84

Neurofibromin, the protein encoded by the NF1 tumor-suppressor gene, negatively regulates the output of p21(ras) (Ras) proteins by accelerating the hydrolysis of active Ras-guanosine triphosphate to inactive Ras-guanosine diphosphate. Children with neurofibromatosis type 1 (NF1) are predisposed to juvenile chronic myelogenous leukemia (JCML) and other malignant myeloid disorders, and heterozygous Nf1 knockout mice spontaneously develop a myeloid disorder that resembles JCML. Both human and murine leukemias show loss of the normal allele. JCML cells and Nf1-/- hematopoietic cells isolated from fetal livers selectively form abnormally high numbers of colonies derived from granulocyte-macrophage progenitors in cultures supplemented with low concentrations of granulocyte-macrophage colony stimulating factor (GM-CSF). Taken together, these data suggest that neurofibromin is required to downregulate Ras activation in myeloid cells exposed to GM-CSF. We have investigated the growth and proliferation of purified populations of hematopoietic progenitor cells isolated from Nf1 knockout mice in response to the cytokines interleukin (IL)-3 and stem cell factor (SCF), as well as to GM-CSF. We found abnormal proliferation of both immature and lineage-restricted progenitor populations, and we observed increased synergy between SCF and either IL-3 or GM-CSF in Nf1-/- progenitors. Nf1-/- fetal livers also showed an absolute increase in the numbers of immature progenitors. We further demonstrate constitutive activation of the Ras-Raf-MAP (mitogen-activated protein) kinase signaling pathway in primary c-kit+ Nf1-/- progenitors and hyperactivation of MAP kinase after growth factor stimulation. The results of these experiments in primary hematopoietic cells implicate Nf1 as playing a central role in regulating the proliferation and survival of primitive and lineage-restricted myeloid progenitors in response to multiple cytokines by modulating Ras output.
 ...
PMID:Nf1 regulates hematopoietic progenitor cell growth and ras signaling in response to multiple cytokines. 960 29

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. KIT and PDGFRA activating mutations are the oncogenic mechanisms in most sporadic GISTs. In addition to sporadic occurrences, GISTs are increasingly being recognized in association with neurofibromatosis type 1 (NF1), yet the underlying pathogenic mechanism remains elusive. To gain an insight into the mechanisms underlying GIST formation in NF1 patients, we studied seven GISTs from three NF1 patients with a combination of different techniques: mutation analysis (KIT, PDGFRA and NF1), western blotting, array CGH and ex vivo imatinib response experiments. We demonstrate that (i) the NF1-related GISTs do not have KIT or PDGFRA mutations, (ii) the molecular event underlying GIST development in this patient group is a somatic inactivation of the wild-type NF1 allele in the tumor and (iii) inactivation of neurofibromin is an alternate mechanism to (hyper) activate the MAP-kinase pathway, while the JAK-STAT3 and PI3K-AKT pathways are less activated in NF1-related GIST compared with sporadic GISTs. In conclusion, we report for the first time the molecular pathogenesis of GISTs in NF1 individuals and demonstrate that this type of tumor clearly belongs to the spectrum of clinical symptoms in NF1.
 ...
PMID:Molecular pathogenesis of multiple gastrointestinal stromal tumors in NF1 patients. 1646 35

RASopathies are a group of disorders characterized by mutations in the RAS-MAPK pathway. RAS-MAP signaling plays a critical role in cell differentiation, proliferation, and survival. Germline mutations can result in distinctive syndromes, including Noonan syndrome, Costello syndrome, and neurofibromatosis type 1. Mosaic RASopathies can present as localized cutaneous lesions like epidermal nevi and nevus sebaceous, or more extensive conditions such as encephalocraniocutaneous lipomatosis. We review the heterogenous presentation of RAS mutations, discuss new targeted therapies, and highlight areas of uncertainty, including carcinogenesis risk and appropriate screening.
 ...
PMID:RASopathies. 3297 3