RESUMO
Neurofibromatosis type 1 (NF1), the most common tumor-predisposing disorder in humans, is caused by defects in the NF1 tumor-suppressor gene. Comprehensive mutation analysis applying RNA-based techniques complemented with FISH analysis achieves mutation detection rates of approximately 95% in NF1 patients. The majority of mutations are minor lesions, and approximately 5% are total gene deletions. We found 13 single- and/or multiexon deletions/duplications out of 1,050 detected mutations using our RNA-based approach in a cohort of 1,100 NF1 patients and confirmed these changes using multiplex ligation-dependent probe amplification (MLPA). With MLPA, we found another 12 novel multiexon deletion/duplications in 55 NF1 patients for whom analysis with multiple assays had not revealed a NF1 mutation, including 50 previously analyzed comprehensively. The extent of the 22 deletions and 3 duplications varied greatly, and there was no clustering of breakpoints. We also evaluated the sensitivity of MLPA in identifying deletions in a mosaic state. Furthermore, we tested whether the MLPA P122 NF1 area assay could distinguish between type I deletions, with breakpoints in low-copy repeats (NF1-LCRs), and type II deletions, caused by aberrant recombination between the JJAZ gene and its pseudogene. Our study showed that intragenic deletions and/or duplications represent only approximately 2% of all NF1 mutations. Although MLPA did not substantially increase the mutation detection rate in NF1 patients, it was a useful first step in a comprehensive mutation analysis scheme to quickly pinpoint patients with single- or multiexon deletions/duplications as well as patients with a total gene deletion who will not need full sequencing of the complete coding region.
Assuntos
Éxons , Mutação , Neurofibromatose 1/genética , Neurofibromina 1/genética , Fatores de Transcrição/genética , Deleção de Genes , Ligação Genética , Humanos , Repetições de Microssatélites , Técnicas de Amplificação de Ácido Nucleico , PseudogenesAssuntos
Deleção de Genes , Genes da Neurofibromatose 1 , Inteligência/genética , Neurofibromatose 1/genética , Adolescente , Adulto , Criança , Feminino , Humanos , MasculinoRESUMO
An NF1 microdeletion is the single most commonly reported mutation in individuals with neurofibromatosis type 1 (NF1). Individuals with an NF1 microdeletion have, as a group, more neurofibromas at a younger age than the group of all individuals with NF1. We report that NF1 microdeletion individuals additionally have a substantially higher lifetime risk for the development of malignant peripheral nerve sheath tumors than individuals with NF1 who do not have an NF1 microdeletion. This should be taken into account in the medical follow-up of individuals with an NF1 microdeletion.
Assuntos
Neoplasias de Bainha Neural/genética , Neurofibromatose 1/genética , Neurofibromina 1/genética , Deleção de Sequência/genética , Adolescente , Adulto , Comorbidade , Humanos , Hibridização in Situ Fluorescente , Pessoa de Meia-Idade , Neoplasias de Bainha Neural/classificação , Reação em Cadeia da Polimerase , Risco , Medição de RiscoRESUMO
We report three cases with a typical diploid/triploid mixoploidy. Cytogenetic analysis showed a normal diploid karyotype in peripheral blood lymphocytes and a mixture of diploid and triploid cells in skin fibroblasts. We analysed microsatellite markers in patients blood lymphocytes and skin fibroblasts and compared the results with the microsatellite markers in the parents. The extra haploid set was in all three cases of maternal origin. In one case the markers were not very informative but in two cases pericentromeric markers showed a single dose of one paternal allele and a double dose of one maternal allele, more telomeric markers showed one paternal allele and two different maternal alleles. These observations can only be explained by the inclusion of the second polar body in one of the blastomeres at the cleavage stage.