Comprehensive NF1 screening on cultured Schwann cells from neurofibromas.
Neurofibromatosis type 1 (NF1) is mainly characterized by the occurrence of benign peripheral nerve sheath tumors or neurofibromas. Thorough investigation of the somatic mutation spectrum has thus far been hampered by the large size of the NF1 gene and the considerable proportion of NF1 heterozygous cells within the tumors. We developed an improved somatic mutation detection strategy on cultured Schwann cells derived from neurofibromas and investigated 38 tumors from nine NF1 patients. Twenty-nine somatic NF1 lesions were detected which represents the highest NF1 somatic mutation detection rate described so far (76%). Furthermore, our data strongly suggest that the acquired second hit underlies reduced NF1 expression in Schwann cell cultures. Together, these data clearly illustrate that two inactivating NF1 mutations, in a subpopulation of the Schwann cells, are required for neurofibroma formation in NF1 tumorigenesis. The observed somatic mutation spectrum shows that intragenic NF1 mutations (26/29) are most prevalent, particularly frameshift mutations (12/29, 41%). We hypothesize that this mutation signature might reflect slightly reduced DNA repair efficiency as a trigger for NF1 somatic inactivation preceding tumorigenesis. Joint analysis of the current and previously published NF1 mutation data revealed a significant difference in the somatic mutation spectrum in patients with a NF1 microdeletion vs. non-microdeletion patients with respect to the prevalence of loss of heterozygosity events (0/15 vs. 41/81). Differences in somatic inactivation mechanism might therefore exist between NF1 microdeletion patients and the general NF1 population.
Maertens
Ophélia
O
Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium.
Brems
Hilde
H
Vandesompele
Jo
J
De Raedt
Thomas
T
Heyns
Ine
I
Rosenbaum
Thorsten
T
De Schepper
Sofie
S
De Paepe
Anne
A
Mortier
Geert
G
Janssens
Sandra
S
Speleman
Frank
F
Legius
Eric
E
Messiaen
Ludwine
L
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000235:genetics; D004252:DNA Mutational Analysis / Q000379:methods; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D018095:Germ-Line Mutation / Q000235:genetics; D006801:Humans; D019656:Loss of Heterozygosity; D018895:Microsatellite Repeats / Q000235:genetics; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D009455:Neurofibroma / Q000235:genetics / Q000473:pathology; D009456:Neurofibromatosis 1 / Q000235:genetics / Q000473:pathology; D025542:Neurofibromin 1 / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012583:Schwann Cells / Q000378:metabolism*; D017384:Sequence Deletion; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D025542:Neurofibromin 1; D009687:Nuclear Proteins; D012333:RNA, Messenger; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein