Linkage disequilibrium and founder effect analysis of the NF1 gene in French Canadians from the Quebec population

We genotyped 19 neurofibromatosis type 1 (NF1) families from French Canadians of the Quebec population with four intragenic microsatellites (IVS26-2.3, IVS27AC28.4, IVS27AC33.1, and IVS38GT53.0). Linkage analysis of the four microsatellite markers among the 19 NF1 families indicates that the four microsatellites are strongly linked with NF1 disease (LOD = 2.76--3.64). The four markers are associated (P = 0--0.077) except marker pair IVS26-2.3/IVS27AC33.1 (P = 0.18 or 0.17). However, perhaps due to the high mutation rate of the NF1 gene, no founder effect for NF1 was detected in the Quebec French Canadians. 2002 ditions scientifiques et mdicales Elsevier SAS. All rights reserved

American Journal of Medical Genetics 104:189198 (2001) Genotype Analysis of the Gene in the French

icrodeletion; French Canadians INTRODUCTION Neurobromatosis type 1 (NF1) is an autosomal dominant disorder that aficts about 1 in 3,500 individuals. NF1 is characterized by cafe-au-lait spots, Lisch nodules and bromatous skin tumors. Patients display assorted medical complications including learning disabilities and malignancy. The NF1 gene spans about 350 kb at 17q11.2 with 60 exons and has a high mutation rate of 1 #10 #4 /gamete/generation leading to approximately 50% sporadic cases. Patients with submicroscopic deletions are remarkable for their severe phenotypes including facial anomalies, early onset (before age 10) of cutaneous neurobromata, and variable cognitive decits ranging from mild learning disabilities to mental retardation. [Kayes et al., 1992, 1994; Wu et al., 1995, 1997a,b; Leppig et al., 1997]. Haploinsufciency for neurobromin is the likely molecular basis of NF1. Theoretically, early age at onset of neurobromagenesis could be attributed to: 1) deletion of th

Jaffe-Campanacci syndrome, revisited: detailed clinical and molecular analyses determine whether patients have neurofibromatosis type 1, coincidental manifestations, or a distinct disorder

Purpose: "Jaffe-Campanacci syndrome" describes the complex of multiple nonossifying fibromas of the long bones, mandibular giant cell lesions, and cafe-au-lait macules in individuals without neurofibromas. We sought to determine whether Jaffe-Campanacci syndrome is a distinct genetic entity or a variant of neurofibromatosis type 1. Methods: We performed germline NF1, SPRED1, and GNAS1 (exon 8) mutation testing on patients with Jaffe-Cainpanacci syndrome of Jaffe-Campanacci syndrome-related features, We also performed somatic NF1 mutation testing on nonossifying fibromas and giant, cell lesions. Results: Pathogenic germline NF1 mutations Were identified 13 of 14 patients with multiple cafe-au-lait macules and niultiple non-ossifying fibromas or giant cell lesions ("classicar Jaffe-Campanacci syndrome); all 13 also fulfilled the National Institues of Health diagnostic criteria for neurofibromatosis type 1. Somatic NFI mutations were detected in two giant cell lesions but not in two nonossifying fibromas. No SPRED1 or GNAS1 (exon 8) mutations were detected in the seven NF1-negative patients with Jaffe-Campanacci syndrome, nonossifying fibromas, or giant cell lesions. Conclusion: In this study, the majority of patients with cafe-au-lait macules and nonossifying fibromas Or giant cell lesions harbored a pathogenic gerinline NF1 mutation,suggesting that many Jaffe-Campanacci syndrome cases may-actually have neurofibromatosis type 1. We provide the first proof of specific somatic second-hit mutations affecting NFI in two giant cell lesions from two unrelated patients, establishing these as neurofibromatosis type 1-associated tumors

Clinical spectrum of individuals with pathogenic NF1 missense variants affecting p.Met1149, p.Arg1276, and p.Lys1423: genotype-phenotype study in neurofibromatosis type 1

We report 281 individuals carrying a pathogenic recurrent NF1 missense variant at p.Met1149, p.Arg1276, or p.Lys1423, representing three nontruncating NF1 hotspots in the University of Alabama at Birmingham (UAB) cohort, together identified in 1.8% of unrelated NF1 individuals. About 25% (95% confidence interval: 20.5-31.2%) of individuals heterozygous for a pathogenic NF1 p.Met1149, p.Arg1276, or p.Lys1423 missense variant had a Noonan-like phenotype, which is significantly more compared with the "classic" NF1-affected cohorts (all p < .0001). Furthermore, p.Arg1276 and p.Lys1423 pathogenic missense variants were associated with a high prevalence of cardiovascular abnormalities, including pulmonic stenosis (all p < .0001), while p.Arg1276 variants had a high prevalence of symptomatic spinal neurofibromas (p < .0001) compared with "classic" NF1-affected cohorts. However, p.Met1149-positive individuals had a mild phenotype, characterized mainly by pigmentary manifestations without externally visible plexiform neurofibromas, symptomatic spinal neurofibromas or symptomatic optic pathway gliomas. As up to 0.4% of unrelated individuals in the UAB cohort carries a p.Met1149 missense variant, this finding will contribute to more accurate stratification of a significant number of NF1 individuals. Although clinically relevant genotype-phenotype correlations are rare in NF1, each affecting only a small percentage of individuals, together they impact counseling and management of a significant number of the NF1 population