Genetic and physical map of the von Recklinghausen neurofibromatosis (NF1) region on chromosome 17

Neurofibromatosis Type 1 with Severe Dystrophic Kyphosis: Surgical Treatment and Prognostic Analysis of 27 Patients

OBJECTIVE

The aim of the present study was to explore the surgical treatment and prognosis of 27 cases of neurofibromatosis type 1 with severe dystrophic kyphosis.

METHODS

We performed surgical treatment for scoliosis and kyphosis caused by dystrophic curves at Peking Union Medical College Hospital, Beijing, China from December 2015 to December 2017. The study included 21 patients with moderate to severe kyphosis, 12 males and 9 females, with an average age of 14.95 ± 6.05 years. All patients had kyphosis angles greater than 70° and had more than four skeletal developmental defects. A total of 6 patients with severe kyphosis, 2 males and 4 females, with an average age of 12.5 years, had more than five skeletal developmental defects with a kyphosis angle greater than 90° or a lumbar kyphosis angle greater than 40°. According to the patient's own situation, we adopted a low-grade surgery scheme (grades 1 or 2) or a high-grade surgery scheme (grades 3-6). The low-grade surgery was mainly lower articular surface resection or pontodestomy, and the high-grade surgery was mainly apical vertebral body or upper discectomy. All patients were followed up to determine their prognosis.

RESULTS

Statistical analysis showed that there was a significant difference in preoperative and postoperative scores between the two groups (P < 0.05), and scoliosis correction showed that surgical treatment had a significant effect on scoliosis kyphosis. The mean follow-up time was 66.7 months. Follow-up results showed that 50% of complications after internal fixation were related to high-level surgery. Complications included displacement of the titanium cage, removal of the lamina hook, formation of pseudoarthrosis, and internal fixation failure (with a rate of 7.7%-14.3%). In contrast, there were no associated symptoms for low-grade surgery. In addition, the results showed that gender, age, extent of resection, height, and body mass index had no significant effect on preoperative, postoperative, and prognostic indicators of patients (P > 0.05).

CONCLUSION

Early identification of dysplastic scoliosis-related deformities plays an important role in surgical planning and prognosis, and low-level surgical procedures are more favorable for patients' prognosis.

Nitric oxide upregulates expression of DNA-PKcs to protect cells from DNA-damaging anti-tumour agents

Nitric-oxide synthase (NOS) activity has been detected in many human tumours, although its function is unclear. Here we show that exposure of cells to nitric oxide (NO) results in a 4-5-fold increase in expression of the DNA-dependent protein-kinase catalytic subunit (DNA-PKcs), one of the key enzymes involved in repairing double-stranded DNA breaks. This NO-mediated increase in enzymatically active DNA-PK not only protects cells from the toxic effects of NO, but also provides crossprotection against clinically important DNA-damaging agents, such as X-ray radiation, adriamycin, bleomycin and cisplatin. The NO-mediated increase in DNA-PKcs described here demonstrates the presence of a new and highly effective NO-mediated mechanism for DNA repair.

Exclusion of the neurofibromatosis 1 locus in a family with inherited café-au-lait spots

We have performed linkage analysis in a small family with autosomal dominant inheritance of multiple café-au-lait spots (CLS) in order to clarify its relationship to classical von Recklinghausen disease (NF 1). We found that an affected woman had transmitted a different haplotype for markers flanking the NF1 gene to both of her affected daughters. These results exclude an allelic mutation of the NF 1 gene on chromosome 17 as the cause for inherited café-au-lait spots in this family.

A somatic cell hybrid map of the long arm of human chromosome 17, containing the familial breast cancer locus (BRCA1)

We describe a detailed somatic cell hybrid map of human chromosome 17q11.2-q23, containing the familial breast and ovarian cancer locus (BRCA1) and highly informative closely linked markers. An X-irradiation panel of 38 hamster/human and mouse/human hybrids with fragments of chromosome 17 was generated and characterized with 22 STS markers from this chromosome. A detailed map of 61 probes onto chromosome 17q, subdividing the chromosome arm into 25 regions, was done by using a panel of hybrids with well-defined breakpoints and nine chromosome-mediated gene transfectants. Our localization of RARA, TOP2, EDH17B1 and 2, and possibly WNT3, between THRA1 and D17S181, two markers known to flank BRCA1, suggests that any of these is a potential candidate for the BRCA1 locus. The marker D17S579 (Mfd188), which is believed to be very close to BRCA1, maps closest to the EDH17B genes.

Molecular characterization of a 17q11.2 translocation in a malignant schwannoma cell line

Malignant schwannomas are soft-tissue neoplasms that occur at increased frequency with germline alterations of the neurofibromatosis-1 (NF1) gene at 17q11.2. We report molecular and cytogenetic characterization of a malignant schwannoma cell line established from an individual affected with NF1. This cell line has a complex hyperdiploid karyotype with two cytogenetically identical der(13)t(13;17)(p11,q11.2) chromosomes. Using somatic cell hybrids, we mapped twelve chromosome-17 probes to either the der(13)t(13;17) chromosome or a small der(17) chromosome. Two chromosome-17p loci, including the p53 tumor suppressor gene, were present in the schwannoma cell line, but did not map to either of these chromosomes. Loss of heterozygosity studies indicated that the two der(13)t(13;17) chromosomes arose by duplication, presumably after the translocation event. The 17q11.2 translocation break-point maps distal to the NF1 gene, and may not disrupt its functioning. Although NF1 mRNA was detected in this cell line by polymerase chain reaction, Northern blot analysis revealed very little or none of the 13-kb mature NF1 transcript. This suggests that the single remaining allele of the NF1 gene contains a mutation that results in either greatly reduced transcription or message instability.

Large de novo DNA deletion in a patient with sporadic neurofibromatosis 1, mental retardation, and dysmorphism

A mildly dysmorphic, mentally retarded male with neurofibromatosis 1 (NF1) was found to have a de novo deletion of chromosome 17. The deletion occurred on the paternally derived chromosome 17 as shown by the absence of a D17S73 paternal allele. Densitometric analysis indicated that, in addition to the D17S73 locus, the patient has only one copy of four other adjacent loci. The deletion involved the loci D17S120, NF1, D17S57, D17S115, and D17S73 and was estimated to encompass more than 380 kb of DNA. The deletion of the entire paternal NF1 allele argues strongly that this disorder is not caused by the action of an abnormal NF1 protein. The extent of the deletion suggests that the mental retardation and dysmorphism of this patient may result from a deletion involving both the NF1 gene and contiguous genetic material.

Loss of NF1 alleles in phaeochromocytomas from patients with type I neurofibromatosis

Type I neurofibromatosis (NF1) is a common autosomal dominant disorder that affects tissues derived from the neural crest. The manifestations are varied, comprising generalised disorders of growth and development as well as an increased risk of benign and malignant tumours including phaeochromocytomas and neurofibrosarcomas. The NF1 locus has been mapped to chromosome bands 17q11-12, and recently the NF1 gene has been cloned. Deletions identified in the constitutional genotype of some patients have suggested that the NF1 phenotype may arise from loss of function mutations of the NF1 gene, consistent with the hypothesis that it is a tumour suppressor gene. To date, however, analysis of NF1 tumours has not revealed the frequent allele losses encompassing the NF1 locus, implying loss of the wild-type NF1 allele, which would support this hypothesis. We report allele losses with markers flanking the NF1 region in each of 7 NF1 phaeochromocytomas. In each of the 3 tumours for which this could be determined, the loss involved the wild-type chromosome. These results provide strong evidence that, in cells of the adrenal medulla at least, the NFI gene may act as a tumour suppressor.

The human vitronectin (complement S-protein) gene maps to the centromeric region of 17q

Vitronectin (complement S-protein, serum-spreading factor, epibolin) is a multifunctional glycoprotein that mediates cell-to-substrate adhesion, inhibits the cytolytic action of the terminal complement cascade in vitro and binds to several serine protease inhibitors of the serpin family, viz. antithrombin III, plasminogen activator inhibitor I (PAI-1) and II (PAI-2), heparin cofactor II and protease nexin. Using high resolution fluorescence in situ hybridization, we mapped the vitronectin gene to the centromeric region of the long arm of chromosome 17 corresponding to 17q11. The location was confirmed by co-hybridization with the centromere-specific alphoid probe p17H8 (D17Z1) and by chromosome banding with 4,6-diamidino-2-phenylindole-dihydrochloride (DAPI). None of the previously mapped genes that are evolutionary related to vitronectin are located on the same chromosome.

A small deletion and an adjacent base exchange in a potential stem-loop region of the neurofibromatosis 1 gene

A single-strand conformational polymorphism found in the DNA of a patient with neurofibromatosis 1 (NF1) was shown to be caused by a deletion of a CCACC or CACCT sequence and an adjacent transversion, located about 500 base pairs downstream from the region that codes for a functional domain of the NF1 gene product. This mutation could also be detected in the patient and in his affected daughter by heteroduplex analysis. The deletion removes the proximal half of a small potential stem-loop and interrupts the reading frame in exon 1. A severely truncated protein with a grossly altered carboxy terminus lacking one third of its sequence is expected to be formed from the mutant allele.

Molecular analysis of acute promyelocytic leukemia breakpoint cluster region on chromosome 17

Acute promyelocytic leukemia (APL; FAB M3) is characterized by a predominance of malignant promyelocytes that carry a reciprocal translocation between the long arms of chromosomes 15 and 17, t(15;17) (q22;q11.2-q12). This translocation has become diagnostic for APL, as it is present in almost 100 percent of cases. A Not I linking clone was used to detect this translocation initially on pulsed-field gel electrophoresis and subsequently with conventional Southern (DNA) analysis. The breakpoints in ten APL cases examined were shown to cluster in a 12-kb region of chromosome 17, containing two CpG-rich islands. The region is the first intron of the retinoic acid receptor alpha gene (RARA).