Neurofibromatosis type I (NFI) in Israeli families: linkage analysis as a diagnostic tool

Neurofibromatosis Type 1 and tumorigenesis: molecular mechanisms and therapeutic implications

Neurofibromatosis Type 1 (NF1) is a common autosomal dominant disease characterized by complex and multicellular neurofibroma tumors, and less frequently by malignant peripheral nerve sheath tumors (MPNSTs) and optic nerve gliomas. Significant advances have been made in elucidating the cellular, genetic, and molecular biology involved in tumor formation in NF1. Neurofibromatosis Type 1 is caused by germline mutations of the NF1 tumor suppressor gene, which generally result in decreased intracellular neurofibromin protein levels, leading to increased cascade Ras signaling to its downstream effectors. Multiple key pathways are involved with the development of tumors in NF1, including Ras/mitogen-activated protein kinase (MAPK) and Akt/mammalian target of rapamycin (mTOR). Interestingly, recent studies demonstrate that multiple other developmental syndromes (in addition to NF1) share phenotypic features resulting from germline mutations in genes responsible for components of the Ras/MAPK pathway. In general, a somatic loss of the second NF1 allele, also referred to as loss of heterozygosity, in the progenitor cell, either the Schwann cell or its precursor, combined with haploinsufficiency in multiple supporting cells is required for tumor formation. Importantly, a complex series of interactions with these other cell types in neurofibroma tumorigenesis is mediated by abnormal expression of growth factors and their receptors and modification of gene expression, a key example of which is the process of recruitment and involvement of the NF1+/– heterozygous mast cell. In general, for malignant transformation to occur, there must be accumulation of additional mutations of multiple genes including INK4A/ARF and P53, with resulting abnormalities of their respective signal cascades. Further, abnormalities of the NF1 gene and molecular cascade described above have been implicated in the tumorigenesis of NF1 and some sporadically occurring gliomas, and thus, these treatment options may have wider applicability. Finally, increased knowledge of molecular and cellular mechanisms involved with NF1 tumorigenesis has led to multiple preclinical and clinical studies of targeted therapy, including the mTOR inhibitor rapamycin, which is demonstrating promising preclinical results for treatment of MPNSTs and gliomas.

Neurofibromatosis 1: analysis of the demand for prenatal diagnosis in a French cohort of 361 patients

The severity of neurofibromatosis 1 and its variable expressivity make prenatal diagnosis appealing. We conducted our research to assess patient characteristics associated with the desire for prenatal diagnosis. Between 1995 and 2004, 361 neurofibromatosis 1 adult patients were interviewed about their desire for prenatal diagnosis. Answers were classified in three groups: (1) 'no;' (2) 'uncertain;' (3) 'yes.' Socio-demographical and clinical data were analyzed by logistic multinomial regression for their association with the desire for prenatal diagnosis. Male-to-female sex ratio was 0.93. Mean age at study +/- SD was 33.5 +/- 10. Seven four patients (20.5%) would consider prenatal diagnosis; 240 (66.5%) did not; and 47 (13.0%) were uncertain. In multivariate analysis, compared to the 'no' group, a longer follow-up (OR = 1.25 [1.11-1.41]), a younger age at study time (OR = 1.25 [1.11-1.41]), not having child (OR = 2.46 [1.03-5.97]) and a higher educational level (OR = 5.07 [1.05-24.47]) were independently associated with the 'yes' group. Compared to the 'no' group individuals who were in the 'uncertain' groups were younger (0.95 [0.90-0.99]), less often married (0.11 [0.01-0.89]) and had a longer follow-up (1.26 [1.09-1.46]). There is a significant demand for prenatal diagnosis among neurofibromatosis 1 French patients. This demand is associated with individuals who are younger, have no child, have a longer follow up, and higher level of education.

Molecular, genetic, and cellular pathogenesis of neurofibromas and surgical implications

Neurofibromatosis 1 (NF1) is a common autosomal dominant disease characterized by complex and multicellular neurofibroma tumors. Significant advances have been made in the research of the cellular, genetic, and molecular biology of NF1. The NF1 gene was identified by positional cloning. The functions of its protein product, neurofibromin, in RAS signaling and in other signal transduction pathways are being elucidated, and the important roles of loss of heterozygosity and haploinsufficiency in tumorigenesis are better understood. The Schwann cell was discovered to be the cell of origin for neurofibromas, but understanding of a more complicated interplay of multiple cell types in tumorigenesis, specifically recruited heterogeneous cell types such as mast cells and fibroblasts, has important implications for surgical therapy of these tumors. This review summarizes the most recent NF1 and neurofibroma literature describing the pathogenesis and treatment of nerve sheath tumors. Understanding the biological underpinnings of tumorigenesis in NF1 has implications for future surgical and medical management of neurofibromas.

Familial café au lait spots: a variant of neurofibromatosis type 1

Café au lait spots (CALS) are a frequent and one of the early manifestations of neurofibromatosis 1 (NF1). However, there are patients with isolated CALS who do not meet the diagnostic criteria for NFI. There are several reports of families in which CALS are inherited as an autosomal dominant trait, without any other features of NFI. In one reported family with dominantly inherited CALS linkage to the NF1 locus was ruled out. In order to elucidate the relationship between familial CALS and NF1 further, we performed a linkage analysis in a large kindred with 11 subjects with CALS in three generations and established close linkage between CALS and five NF1 intragenic polymorphisms. We propose that in this family the trait of CALS is allelic to NF1, it is fully penetrant, and it does not confer a risk of other NF1 symptoms.