Von Recklinghausen neurofibromatosis (NF1) is a common autosomal dominant disorder characterized by abnormalities in multiple tissues derived from the neural crest. No reliable cellular phenotypic marker has been identified, which has hampered direct efforts to identify the gene. The chromosome location of the NF1 gene has been previously mapped genetically to 17q11.2, and data from two NF1 patients with balanced translocations in this region have further narrowed the candidate interval. The use of chromosome jumping and yeast artificial chromosome technology has now led to the identification of a large (approximately 13 kilobases) ubiquitously expressed transcript (denoted NF1LT) from this region that is definitely interrupted by one and most likely by both translocations. Previously identified candidate genes, which failed to show abnormalities in NF1 patients, are apparently located within introns of NF1LT, on the antisense strand. A new mutation patient with NF1 has been identified with a de novo 0.5-kilobase insertion in the NF1LT gene. These observations, together with the high spontaneous mutation rate of NF1 (which is consistent with a large locus), suggest that NF1LT represents the elusive NF1 gene.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder with a high mutation rate and variable expression, characterized by neurofibromas, café-au-lait spots, Lisch nodules of the iris, and less frequent features including bone deformities and learning disabilities. The recently cloned NF1 gene encodes a transcript of 13 kilobases from a ubiquitously expressed locus on chromosome 17. Most NF1 patients are expected to have unique mutations, but only a few have so far been characterized, restricting genetic and functional information and the design of DNA diagnostics. We report an unusual NF1 mutation, that of a de novo Alu repetitive element insertion into an intron, which results in deletion of the downstream exon during splicing and consequently shifts the reading frame. This previously undescribed mechanism of mutation indicates that Alu retrotransposition is an ongoing process in the human germ line.

Von Recklinghausen neurofibromatosis, or type 1 neurofibromatosis (NF1), is a common autosomal dominant disorder characterized by abnormalities in multiple tissues derived from the embryonic neural crest. Portions of the gene have been recently identified by positional cloning, and sequence analysis has shown homology to the GTPase activating protein (GAP) family. In this report we present the results of an extensive cDNA walk resulting in the cloning of the complete coding region of the NF1 transcript. Analysis of the sequences reveals an open reading frame of 2818 amino acids, although alternatively spliced products may code for different protein isoforms. The gene extends for approximately 300 kb on chromosome 17, with its promoter in a CpG-rich island.

Von Recklinghausen neurofibromatosis (NF1) is a common autosomal dominant disorder mapped to 17q11.2 and typically characterized by the occurrence of neural crest-derived tumors. The gene has recently been cloned using reverse genetics or "positional cloning" approaches. Its function, however, remains unknown. We have performed cytogenetic and molecular analyses on 9 malignant tumors from NF1 patients to look for loss of alleles or chromosome rearrangements involving chromosome 17 to test the hypothesis that the NF1 gene acts as a recessive "tumor suppressor" gene. Loss of alleles on this chromosome was detected for 3 of 9 malignant tumors. Two peripheral nerve sheath tumors showed allele loss at informative loci on both the long and short arms of chromosome 17. In contrast, a glioblastoma with focal gliosarcoma showed loss of heterozygosity on the short arm of chromosome 17 only, and not at loci on the long arm. One nerve sheath tumor was previously shown by direct sequence analysis to have a point mutation at the TP53 locus at 17p13. These data support a role for the TP53 gene or other genes on the short arm of chromosome 17 in at least some malignancies in NF1. Six other neurofibrosarcomas showed no allele loss at informative loci on chromosome 17. Cytogenetic analysis was performed on 7 tumors, including 2 with allele loss. The two tumors with allele loss showed abnormal karyotypes while all others were normal. Southern blot and pulsed-field gel analysis using probes within or closely linked to the NF1 locus detected no gross deletions or rearrangements in the tumors studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder characterized by progressive and variable involvement of tissues predominantly derived from the neural crest and a predisposition toward malignancies. The NF1 gene encodes neurofibromin, a GTPase-activating protein containing a GAP-related domain (NF1-GRD) that is capable of down-regulating ras by stimulating its intrinsic GTPase activity. We report a homozygous deletion of most of NF1 in one of eight malignant melanoma cell lines leading to loss of detectable mRNA and protein, as well as the apparent absence of protein and mRNA in another melanoma. This data suggests that NF1 can function as a tumour suppressor gene in the development or progression of malignant melanoma.

Hemophilia A (HA) is a bleeding disorder resulting from deficient Factor VIII (FVIII), which normally functions as a cofactor to activated Factor IX (FIXa) that facilitates activation of Factor X (FX). To mimic this property in a bispecific antibody (biAb) format, a screening was conducted to identify functional pairs of anti-FIXa and anti-FX antibodies, followed by optimization of functional and biophysical properties. The resulting biAb (Mim8) assembled efficiently with FIXa and FX on membranes, and supported activation with an apparent equilibrium dissociation constant (KD) of 16 nM. Binding affinity with FIXa and FX in solution was much lower, with KD-values for FIXa and FX of 2.3 and 1.5 µM, respectively. In addition, the activity of Mim8 was dependent on stimulatory activity contributed by the anti-FIXa arm, which enhanced the proteolytic activity of FIXa by four orders of magnitude. In hemophilia A plasma and whole blood, Mim8 normalized thrombin generation and clot formation with potencies 13 and 18 times higher than a sequence-identical analog of emicizumab, respectively. A similar potency difference was observed in a tail-vein transection model in hemophilia A mice, while reduction of bleeding in a severe tail-clip model was observed only for Mim8. Furthermore, the pharmacokinetics of Mim8 were investigated and a half-life of 14 days demonstrated in cynomolgus monkey. In conclusion, Mim8 is a FVIIIa-mimetic with a potent and efficacious hemostatic effect based on preclinical data.

The gene responsible for neurofibromatosis type 1 (NF1), one of the more common inherited human disorders, was identified recently, and segments of it were cloned. Two translocation breakpoints that interrupt the NF1 gene in NF1 patients flank a 60-kb segment of DNA that contains the EV12A locus (previously reported as the EV12 locus), the human homolog of a mouse gene, Evi-2A, implicated in retrovirus-induced murine myeloid tumors. EVI2A lies within an intron of the NF1 gene and is transcribed from telomere toward centromere, opposite to the direction of transcription of the NF1 gene. Here we describe a second locus, EVI2B, also located between the two NF1 translocation breakpoints. Full-length cDNAs from the EV12B locus detect a 2.1-kb transcript in bone marrow, peripheral blood mononuclear cells, and fibroblasts. Sequencing studies predict an EV12B protein of 448 amino acids that is proline-rich and contains an N-terminal signal peptide, an extracellular domain with four potential glycosylation sites, a single hydrophobic transmembrane domain, and a cytoplasmic hydrophilic domain. At the level of genomic DNA the EV12B locus lies within the same intron of the NF1 gene as EV12A and contains a 57-bp 5' exon that is noncoding, an 8-kb intron, and a 2078-bp 3' exon that includes the entire open reading frame. EV12B is transcribed in the same direction as EV12A; its 5' exon lies only 4 kb downstream from the 3' exon of the EV12A locus. In the mouse the 5' exon of the homologous gene, Evi-2B, lies approximately 2.8 kb from the 3' end of Evi-2A, in the midst of a cluster of viral integration sites identified in retrovirus-induced myeloid tumors; thus, Evi-2B may function as an oncogene in these tumors.

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