Type 2 NF1 Deletions Are Highly Unusual by Virtue of the Absence of Nonallelic Homologous Recombination Hotspots and an Apparent Preference for Female Mitotic Recombination
2007; Elsevier BV; Volume: 81; Issue: 6 Linguagem: Inglês
10.1086/522089
ISSN1537-6605
AutoresKatharina Steinmann, D.N. Cooper, Lan Kluwe, Nadia Chuzhanova, Cornelia Senger, Eduard Serra, Conxi Lázaro, Montserrat Gilaberte, Katharina Wimmer, Viktor-Felix Mautner, Hildegard Kehrer‐Sawatzki,
Tópico(s)Genomic variations and chromosomal abnormalities
ResumoApproximately 5% of patients with neurofibromatosis type 1 (NF1) exhibit gross deletions that encompass the NF1 gene and its flanking regions. The breakpoints of the common 1.4-Mb (type 1) deletions are located within low-copy repeats (NF1-REPs) and cluster within a 3.4-kb hotspot of nonallelic homologous recombination (NAHR). Here, we present the first comprehensive breakpoint analysis of type 2 deletions, which are a second type of recurring NF1 gene deletion. Type 2 deletions span 1.2 Mb and are characterized by breakpoints located within the SUZ12 gene and its pseudogene, which closely flank the NF1-REPs. Breakpoint analysis of 13 independent type 2 deletions did not reveal any obvious hotspots of NAHR. However, an overrepresentation of polypyrimidine/polypurine tracts and triplex-forming sequences was noted in the breakpoint regions that could have facilitated NAHR. Intriguingly, all 13 type 2 deletions identified so far are characterized by somatic mosaicism, which indicates a positional preference for mitotic NAHR within the NF1 gene region. Indeed, whereas interchromosomal meiotic NAHR occurs between the NF1-REPs giving rise to type 1 deletions, NAHR during mitosis appears to occur intrachromosomally between the SUZ12 gene and its pseudogene, thereby generating type 2 deletions. Such a clear distinction between the preferred sites of mitotic versus meiotic NAHR is unprecedented in any other genomic disorder induced by the local genomic architecture. Additionally, 12 of the 13 mosaic type 2 deletions were found in females. The marked female preponderance among mosaic type 2 deletions contrasts with the equal sex distribution noted for type 1 and/or atypical NF1 deletions. Although an influence of chromatin structure was strongly suspected, no sex-specific differences in the methylation pattern exhibited by the SUZ12 gene were apparent that could explain the higher rate of mitotic recombination in females. Approximately 5% of patients with neurofibromatosis type 1 (NF1) exhibit gross deletions that encompass the NF1 gene and its flanking regions. The breakpoints of the common 1.4-Mb (type 1) deletions are located within low-copy repeats (NF1-REPs) and cluster within a 3.4-kb hotspot of nonallelic homologous recombination (NAHR). Here, we present the first comprehensive breakpoint analysis of type 2 deletions, which are a second type of recurring NF1 gene deletion. Type 2 deletions span 1.2 Mb and are characterized by breakpoints located within the SUZ12 gene and its pseudogene, which closely flank the NF1-REPs. Breakpoint analysis of 13 independent type 2 deletions did not reveal any obvious hotspots of NAHR. However, an overrepresentation of polypyrimidine/polypurine tracts and triplex-forming sequences was noted in the breakpoint regions that could have facilitated NAHR. Intriguingly, all 13 type 2 deletions identified so far are characterized by somatic mosaicism, which indicates a positional preference for mitotic NAHR within the NF1 gene region. Indeed, whereas interchromosomal meiotic NAHR occurs between the NF1-REPs giving rise to type 1 deletions, NAHR during mitosis appears to occur intrachromosomally between the SUZ12 gene and its pseudogene, thereby generating type 2 deletions. Such a clear distinction between the preferred sites of mitotic versus meiotic NAHR is unprecedented in any other genomic disorder induced by the local genomic architecture. Additionally, 12 of the 13 mosaic type 2 deletions were found in females. The marked female preponderance among mosaic type 2 deletions contrasts with the equal sex distribution noted for type 1 and/or atypical NF1 deletions. Although an influence of chromatin structure was strongly suspected, no sex-specific differences in the methylation pattern exhibited by the SUZ12 gene were apparent that could explain the higher rate of mitotic recombination in females. Deletions in 17q11.2 that encompass the NF1 gene and its flanking regions constitute the most frequently recurring mutations that cause neurofibromatosis type 1 (NF1 [MIM +162200]). Indeed, ∼5% of all patients with NF1 exhibit deletions of this chromosomal region.1Cnossen MH van der Est MN Breuning MH van Asperen CJ Breslau-Siderius EJ van der Ploeg AT de Goede-Bolder A van den Ouweland AM Halley DJ Niermeijer MF Deletions spanning the neurofibromatosis type 1 gene: implications for genotype-phenotype correlations in neurofibromatosis type 1?.Hum Mutat. 1997; 9: 458-464Crossref PubMed Scopus (92) Google Scholar, 2Rasmussen SA Colman SD Ho VT Abernathy CR Arn PH Weiss L Schwartz C Saul RA Wallace MR Constitutional and mosaic large NF1 gene deletions in neurofibromatosis type 1.J Med Genet. 1998; 35: 468-471Crossref PubMed Scopus (66) Google Scholar, 3Kluwe L Siebert R Gesk S Friedrich RE Tinschert S Kehrer-Sawatzki H Mautner V-F Screening of 500 unselected neurofibromatosis 1 patients for deletions of the NF1 gene.Hum Mutat. 2004; 23: 111-116Crossref PubMed Scopus (130) Google Scholar Three subtypes of these gross NF1 gene deletions have been noted that differ in terms of deletion size and the positions of their respective breakpoints: type 1, type 2, and atypical NF1 deletions. The most common of these are type 1 deletions, which encompass 1.4 Mb and lead to the loss of 14 genes, including NF1. Type 1 deletions are mediated by nonallelic homologous recombination (NAHR) between low-copy repeats flanking the NF1 gene region, termed NF1-REPs A and C.4Dorschner MO Sybert VP Weaver M Pletcher BA Stephens K NF1 microdeletion breakpoints are clustered at flanking repetitive sequences.Hum Mol Genet. 2000; 9: 35-46Crossref PubMed Scopus (148) Google Scholar, 5Jenne DE Tinschert S Reimann H Lasinger W Thiel G Hameister H Kehrer-Sawatzki H Molecular characterization and gene content of breakpoint boundaries in patients with neurofibromatosis type 1 with 17q11.2 microdeletions.Am J Hum Genet. 2001; 69: 516-527Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar, 6López-Correa C Dorschner M Brems H Lazaro C Clementi M Upadhyaya M Dooijes D Moog U Kehrer-Sawatzki H Rutkowski JL et al.Recombination hotspot in NF1 microdeletion patients.Hum Mol Genet. 2001; 10: 1387-1392Crossref PubMed Scopus (142) Google Scholar, 7Forbes SH Dorschner MO Le R Stephens K Genomic context of paralogous recombination hotspots mediating recurrent NF1 region microdeletion.Genes Chrom Cancer. 2004; 41: 12-25Crossref PubMed Scopus (35) Google Scholar, 8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar, 9De Raedt T Stephens M Heyns I Brems H Thijs D Messiaen L Stephens K Lazaro C Wimmer K Kehrer-Sawatzki H et al.Conservation of hotspots for recombination in low-copy repeats associated with the NF1 microdeletion.Nat Genet. 2006; 38: 1419-1423Crossref PubMed Scopus (70) Google Scholar Two preferred regions of NAHR have been noted within the NF1-REPs: the paralogous recombination sites PRS1 and PRS2.7Forbes SH Dorschner MO Le R Stephens K Genomic context of paralogous recombination hotspots mediating recurrent NF1 region microdeletion.Genes Chrom Cancer. 2004; 41: 12-25Crossref PubMed Scopus (35) Google Scholar, 9De Raedt T Stephens M Heyns I Brems H Thijs D Messiaen L Stephens K Lazaro C Wimmer K Kehrer-Sawatzki H et al.Conservation of hotspots for recombination in low-copy repeats associated with the NF1 microdeletion.Nat Genet. 2006; 38: 1419-1423Crossref PubMed Scopus (70) Google Scholar Of 60 type 1 deletions so far investigated, 40 have had breakpoints within a 3.4-kb region spanning PRS2.9De Raedt T Stephens M Heyns I Brems H Thijs D Messiaen L Stephens K Lazaro C Wimmer K Kehrer-Sawatzki H et al.Conservation of hotspots for recombination in low-copy repeats associated with the NF1 microdeletion.Nat Genet. 2006; 38: 1419-1423Crossref PubMed Scopus (70) Google Scholar Thus, PRS2 clearly constitutes a hotspot for NAHR within NF1-REPs A and C. Of the 60 type 1 deletions, 13 have had breakpoints within PRS1, a 1.8-kb region that represents a second preferred site for NAHR within the NF1-REPs. Importantly, NAHR underlying type 1 deletions occurs preferentially during maternal meiosis.10Lazaro C Gaona A Ainsworth P Tenconi R Vidaud D Kruyer H Ars E Volpini V Estivill X Sex differences in mutational rate and mutational mechanism in the NF1 gene in neurofibromatosis type 1 patients.Hum Genet. 1996; 98: 696-699Crossref PubMed Scopus (78) Google Scholar, 11Upadhyaya M Ruggieri M Maynard J Osborn M Hartog C Mudd S Penttinen M Cordeiro I Ponder M Ponder BA et al.Gross deletions of the neurofibromatosis type 1 (NF1) gene are predominantly of maternal origin and commonly associated with a learning disability, dysmorphic features and developmental delay.Hum Genet. 1998; 102: 591-597Crossref PubMed Scopus (133) Google Scholar, 12López-Correa C Brems H Lazaro C Marynen P Legius E Unequal meiotic crossover: a frequent cause of NF1 microdeletions.Am J Hum Genet. 2000; 66: 1969-1974Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar Atypical NF1 deletions are rather less common than type 1 deletions, and most have nonrecurrent breakpoints.1Cnossen MH van der Est MN Breuning MH van Asperen CJ Breslau-Siderius EJ van der Ploeg AT de Goede-Bolder A van den Ouweland AM Halley DJ Niermeijer MF Deletions spanning the neurofibromatosis type 1 gene: implications for genotype-phenotype correlations in neurofibromatosis type 1?.Hum Mutat. 1997; 9: 458-464Crossref PubMed Scopus (92) Google Scholar, 4Dorschner MO Sybert VP Weaver M Pletcher BA Stephens K NF1 microdeletion breakpoints are clustered at flanking repetitive sequences.Hum Mol Genet. 2000; 9: 35-46Crossref PubMed Scopus (148) Google Scholar, 11Upadhyaya M Ruggieri M Maynard J Osborn M Hartog C Mudd S Penttinen M Cordeiro I Ponder M Ponder BA et al.Gross deletions of the neurofibromatosis type 1 (NF1) gene are predominantly of maternal origin and commonly associated with a learning disability, dysmorphic features and developmental delay.Hum Genet. 1998; 102: 591-597Crossref PubMed Scopus (133) Google Scholar, 13Kayes LM Riccardi VM Burke W Bennett RL Stephens K Large de novo DNA deletion in a patient with sporadic neurofibromatosis 1, mental retardation, and dysmorphism.J Med Genet. 1992; 29: 686-690Crossref PubMed Scopus (55) Google Scholar, 14Kayes LM Burke W Riccardi VM Benett R Ehrlich P Rubinstein A Stephens K Deletions spanning the neurofibromatosis I gene: identification and phenotype of five patients.Am J Hum Genet. 1994; 54: 424-436PubMed Google Scholar, 15Riva P Corrado L Natacci F Castorina P Wu BL Schneider GH Clementi M Tenconi R Korf BR Larizza L NF1 microdeletion syndrome: refined FISH characterization of sporadic and familial deletions with locus-specific probes.Am J Hum Genet. 2000; 66: 100-109Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar, 16Jenne DE Tinschert S Dorschner MO Hameister H Stephens K Kehrer-Sawatzki H Complete physical map and gene content of the human NF1 tumor suppressor region in human and mouse.Genes Chrom Cancer. 2003; 37: 111-120Crossref PubMed Scopus (39) Google Scholar, 17Kehrer-Sawatzki H Tinschert S Jenne DE Heterogeneity of breakpoints in non-LCR-mediated large constitutional deletions of the 17q11.2 NF1 tumour suppressor region.J Med Genet. 2003; 40: E116Crossref PubMed Scopus (21) Google Scholar, 18Kehrer-Sawatzki H Kluwe L Funsterer C Mautner VF Extensively high load of internal tumors determined by whole body MRI scanning in a patient with neurofibromatosis type 1 and a non-LCR-mediated 2-Mb deletion in 17q11.2.Hum Genet. 2005; 116: 466-475Crossref PubMed Scopus (34) Google Scholar, 19Venturin M Gervasini C Orzan F Bentivegna A Corrado L Colapietro P Friso A Tenconi R Upadhyaya M Larizza L et al.Evidence for non-homologous end joining and non-allelic homologous recombination in atypical NF1 microdeletions.Hum Genet. 2004; 115: 69-80Crossref PubMed Scopus (34) Google Scholar, 20Mantripragada KK Thuresson AC Piotrowski A Diaz de Stahl T Menzel U Grigelionis G Ferner RE Griffiths S Bolund L Mautner V et al.Identification of novel deletion breakpoints bordered by segmental duplications in the NF1 locus using high resolution array-CGH.J Med Genet. 2006; 43: 28-38Crossref PubMed Scopus (45) Google Scholar Type 2 deletions constitute the second-most-common type of gross NF1 gene deletion. They span 1.2 Mb and are characterized by breakpoints within the SUZ12 gene (GenBank accession number NM_015355) and its pseudogene (SUZ12P [GenBank accession number BC047718]). SUZ12 is separated from NF1-REP C by 30 kb, whereas an overlap of 4 kb exists between SUZ12P and NF1-REP A (fig. 1). Type 2 deletions lead to the loss of 13 genes; in contrast to type 1 deletions, the functional LRRC37B gene within the distal NF1-REP C is retained in type 2 deletions. A total of 13 patients with type 2 deletions have been reported in the literature to date.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar, 21Petek E Jenne DE Smolle J Binder B Lasinger W Windpassinger C Wagner K Kroisel PM Kehrer-Sawatzki H Mitotic recombination mediated by the JJAZF1 (KIAA0160) gene causing somatic mosaicism and a new type of constitutional NF1 microdeletion in two children of a mosaic female with only few manifestations.J Med Genet. 2003; 40: 520-525Crossref PubMed Google Scholar, 22Spiegel M Oexle K Horn D Windt E Buske A Albrecht B Prott EC Seemanova E Seidel J Rosenbaum T et al.Childhood overgrowth in patients with common NF1 microdeletions.Eur J Hum Genet. 2005; 13: 883-888Crossref PubMed Scopus (37) Google Scholar Since 6 of these 13 patients constitute mother-child pairs, they actually represent only 10 independent type 2 deletions. Remarkably, 8 of these 10 patients with type 2 deletions were somatic mosaics.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar, 21Petek E Jenne DE Smolle J Binder B Lasinger W Windpassinger C Wagner K Kroisel PM Kehrer-Sawatzki H Mitotic recombination mediated by the JJAZF1 (KIAA0160) gene causing somatic mosaicism and a new type of constitutional NF1 microdeletion in two children of a mosaic female with only few manifestations.J Med Genet. 2003; 40: 520-525Crossref PubMed Google Scholar Because of this somatic mosaicism, patients with type 2 deletions frequently exhibit milder clinical manifestations of NF1. This might result in an ascertainment bias and could therefore explain the relatively small number of patients who have received a diagnosis of type 2 deletions, as compared with type 1 deletions, which are constitutional and hence are associated with a more severe clinical phenotype. So far, no somatic (mosaic) type 1 deletions have been identified unequivocally. The relatively small number of reported subjects with type 2 deletions might also be because somatic mosaicism is more difficult to detect, in practical terms. In addition to a possible ascertainment bias due to the milder clinical phenotype, the structure, relative target size, and degree of homology between the two sets of repeats (NF1-REPs and SUZ12/SUZ12P) could also be responsible for the higher frequency of type 1 deletions as compared with type 2 deletions. The SUZ12 gene and its pseudogene SUZ12P constitute direct continuous repeats that display 96.2% sequence identity over a length of 45 kb. By contrast, the NF1-REPs are longer, and their structure is more complicated, in that they are composed of homology blocks or subunits separated by nonhomologous regions.5Jenne DE Tinschert S Reimann H Lasinger W Thiel G Hameister H Kehrer-Sawatzki H Molecular characterization and gene content of breakpoint boundaries in patients with neurofibromatosis type 1 with 17q11.2 microdeletions.Am J Hum Genet. 2001; 69: 516-527Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar, 6López-Correa C Dorschner M Brems H Lazaro C Clementi M Upadhyaya M Dooijes D Moog U Kehrer-Sawatzki H Rutkowski JL et al.Recombination hotspot in NF1 microdeletion patients.Hum Mol Genet. 2001; 10: 1387-1392Crossref PubMed Scopus (142) Google Scholar, 7Forbes SH Dorschner MO Le R Stephens K Genomic context of paralogous recombination hotspots mediating recurrent NF1 region microdeletion.Genes Chrom Cancer. 2004; 41: 12-25Crossref PubMed Scopus (35) Google Scholar, 16Jenne DE Tinschert S Dorschner MO Hameister H Stephens K Kehrer-Sawatzki H Complete physical map and gene content of the human NF1 tumor suppressor region in human and mouse.Genes Chrom Cancer. 2003; 37: 111-120Crossref PubMed Scopus (39) Google Scholar, 23De Raedt T Brems H Lopez-Correa C Vermeesch JR Marynen P Legius E Genomic organization and evolution of the NF1 microdeletion region.Genomics. 2004; 84: 346-360Crossref PubMed Scopus (32) Google Scholar NF1-REP A spans 131 kb, whereas NF1-REP C encompasses 75 kb. The largest homology block shared by NF1-REP A and NF1-REP C spans 51 kb and harbors both PRS1 and PRS2. Within this homology block, the sequence identity is 97.5%,7Forbes SH Dorschner MO Le R Stephens K Genomic context of paralogous recombination hotspots mediating recurrent NF1 region microdeletion.Genes Chrom Cancer. 2004; 41: 12-25Crossref PubMed Scopus (35) Google Scholar slightly higher than the 96.2% identity observed between SUZ12 and SUZ12P. Until now, the breakpoint regions of only three type 2 deletions have been precisely determined at the DNA sequence level.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar, 21Petek E Jenne DE Smolle J Binder B Lasinger W Windpassinger C Wagner K Kroisel PM Kehrer-Sawatzki H Mitotic recombination mediated by the JJAZF1 (KIAA0160) gene causing somatic mosaicism and a new type of constitutional NF1 microdeletion in two children of a mosaic female with only few manifestations.J Med Genet. 2003; 40: 520-525Crossref PubMed Google Scholar It has therefore been unclear whether hotspots of recombination occur within the SUZ12 sequences as they do in type 1 deletions, whose breakpoints cluster tightly within the NF1-REPs. In this study, we have identified the sites of recombination underlying the remaining seven uncharacterized type 2 deletions identified in earlier studies.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar, 22Spiegel M Oexle K Horn D Windt E Buske A Albrecht B Prott EC Seemanova E Seidel J Rosenbaum T et al.Childhood overgrowth in patients with common NF1 microdeletions.Eur J Hum Genet. 2005; 13: 883-888Crossref PubMed Scopus (37) Google Scholar Further, we characterized the breakpoints of three novel, hitherto-unreported type 2 deletions. The comparative analysis of the deletion breakpoint regions has revealed profound differences between type 1 and type 2 deletions, particularly with respect to their underlying mutational mechanisms. Elsewhere, 13 patients with type 2 deletions were identified by use of FISH analysis.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar, 21Petek E Jenne DE Smolle J Binder B Lasinger W Windpassinger C Wagner K Kroisel PM Kehrer-Sawatzki H Mitotic recombination mediated by the JJAZF1 (KIAA0160) gene causing somatic mosaicism and a new type of constitutional NF1 microdeletion in two children of a mosaic female with only few manifestations.J Med Genet. 2003; 40: 520-525Crossref PubMed Google Scholar, 22Spiegel M Oexle K Horn D Windt E Buske A Albrecht B Prott EC Seemanova E Seidel J Rosenbaum T et al.Childhood overgrowth in patients with common NF1 microdeletions.Eur J Hum Genet. 2005; 13: 883-888Crossref PubMed Scopus (37) Google Scholar Here, we report three further patients in whom type 2 deletions have been identified by FISH (patients 1104, 1630, and 1502). Patients 1630 and 1502 were referred to the NF1 Clinic in Hamburg, whereas patient 1104 presented at the Department of Dermatology (Hospital del Mar-Institut Municipal d'Assistència Sanitària, Barcelona). DNA was extracted from patient material after receipt of informed consent. The clinical phenotypes of these three patients are given in table 1. All 16 known patients with type 2 deletions are listed in table 2. Of these 16 patients, 6 constitute mother-child pairs (three sets). To identify the breakpoint regions of the 10 as-yet-uncharacterized type 2 deletions, several different methods were employed (summarized in table 3). In nine cases, the breakpoints were narrowed down by sequence analysis of PCR fragments amplified from somatic-cell hybrids harboring only the deletion-containing chromosome 17. The primer sequences used to refine the respective deletion breakpoints are listed in table 4. PCR products were sequenced by means of an ABI Prism 3100 Genetic Analyzer (Applied Biosystems). To determine whether the amplified PCR fragments were derived from the SUZ12 gene or the SUZ12 pseudogene, paralogous sequence variants (PSVs) were analyzed as described elsewhere.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google ScholarTable 1Clinical Phenotype of Three Newly Reported Female Patients with NF1 and Mosaic Type 2 DeletionsPatientAge (years)Clinical Investigation and Phenotype110436The patient consulted the dermatologist with respect to hyperpigmented macules, present since birth, and papulonodular lesions on macules and normal skin, which had appeared during her adolescence. Physical examination revealed hyperpigmented brownish areas with a chessboard pattern on the skin of the upper back, left shoulder, left arm, left breast, right shoulder, lumbar region, and right side of the abdomen. Axillary and inguinal freckling was absent. Four to six soft, skin-colored papulonodular lesions, 1–3 cm in diameter, were noted on the abdomen, thighs, and forearms. The histopathological investigation of one of these lesions confirmed the clinical diagnosis of a neurofibroma. Results of ophthalmological examination for Lisch nodules were negative. Abnormalities of her bones were excluded by x-ray analysis. Neurological and audiological examination also failed to reveal any anomalies. Magnetic resonance imaging (MRI) of the CNS detected multiple bihemispheric white-substance subcortical lesions, probably of vascular etiology. The angiography MRI results were, however, normal. The patient had never experienced any symptoms of stroke or neurological disease, nor was there any family history of neurofibromatosis. Her two children, aged 9 and 5 years, exhibited only light hyperpigmentation on the abdomen, as well as two and one café-au-lait spots, respectively. Results of ophthalmological examination of the children for Lisch nodules were negative, and neurological examination revealed no abnormalities.150226The patient was 168 cm in height and weighed 58 kg. Axillary and inguinal freckling and multiple café-au-lait spots but <10 subcutaneous neurofibromas were noted. She had attended secondary school but had an IQ of 90. Cerebral and whole-body MRI scans did not reveal any tumors or other anomalies. Dysmorphic facial features were not noted.163015The patient had more than six café-au-lait spots and axillary freckling but no confirmed neurofibromas, no large hands and feet, and none of the other features frequently seen in patients with gross NF1 deletions. The patient was 176 cm in height, weighed 54 kg, and attended secondary school. Open table in a new tab Table 2Mosaicism in the 16 Identified Patients with Type 2 Deletions, as Determined by FISH and PCR AnalysisPercentage of Cells with Deletion inBlood CellsPatientMosaicSexCulturedUnculturedBuccal SmearFibroblastsNeurofibromaUrine811 (daughter)NoF100……………811-MaThe mosaic mother passed the deletion to her offspring.,bInvestigated in this study. (mother)YesF93……………KCD-3cAs described elsewhere.8YesF92……51……697cAs described elsewhere.8YesF97…59………736cAs described elsewhere.8YesF94…59………1630bInvestigated in this study.YesF92……………IL39-III2 (son)NoM100……………IL39aThe mosaic mother passed the deletion to her offspring.,dAs described elsewhere.21 (mother)YesF70……15……1104bInvestigated in this study.YesF84948……15SB (daughter)NoF100……………WBaThe mosaic mother passed the deletion to her offspring.,cAs described elsewhere.8 (mother)YesF94……………938cAs described elsewhere.8YesF91…80………1502bInvestigated in this study.YesF97…70………488cAs described elsewhere.8YesF98…56………928cAs described elsewhere.8YesF100…55…80…HCcAs described elsewhere.8,ePCR analysis of polymorphic markers, performed using DNA extracted from buccal smears, indicated that patient HC also exhibits somatic mosaicism.YesM100……………Note.—FISH was performed with BAC RP11-142O6 (GenBank accession number AC079915), which spans the proximal portion of the NF1 gene, and BAC RP11-55A13 from 17q24. An ellipsis (…) = not determined.a The mosaic mother passed the deletion to her offspring.b Investigated in this study.c As described elsewhere.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholard As described elsewhere.21Petek E Jenne DE Smolle J Binder B Lasinger W Windpassinger C Wagner K Kroisel PM Kehrer-Sawatzki H Mitotic recombination mediated by the JJAZF1 (KIAA0160) gene causing somatic mosaicism and a new type of constitutional NF1 microdeletion in two children of a mosaic female with only few manifestations.J Med Genet. 2003; 40: 520-525Crossref PubMed Google Scholare PCR analysis of polymorphic markers, performed using DNA extracted from buccal smears, indicated that patient HC also exhibits somatic mosaicism. Open table in a new tab Table 3Methods Employed to Identify the Breakpoint Regions in 13 Patients with Type 2 DeletionsBreakpoint Regions Identified byPatientBreakpoint Region IdentifiedPCR Analysis of Somatic-Cell HybridsaSomatic-cell hybrids containing only the deletion-bearing chromosome 17 were analyzed by sequence analysis of the PCR products. Evaluation of PSVs that give rise to differences between the SUZ12 pseudogene and the functional SUZ12 gene potentiated the approximate demarcation of the region of recombination in each case.Deletion-Junction PCRbPrimers were designed to allow specific amplification across the breakpoint regions, with the forward primer located in the SUZ12 pseudogene and the reverse primer in the functional SUZ12 gene. Sequence analysis confirmed that the proximal sequences of the breakpoint-spanning fragments are homologous to SUZ12P (represented by GenBank accession number AC127024), whereas the sequences at the distal end are homologous to the SUZ12 gene (GenBank accession number AC090616.12).Array CGH811This study−+−KCD-3Kehrer-Sawatzki et al.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar++−697This study++−736This study−++1630This study−++IL39Petek et al.21Petek E Jenne DE Smolle J Binder B Lasinger W Windpassinger C Wagner K Kroisel PM Kehrer-Sawatzki H Mitotic recombination mediated by the JJAZF1 (KIAA0160) gene causing somatic mosaicism and a new type of constitutional NF1 microdeletion in two children of a mosaic female with only few manifestations.J Med Genet. 2003; 40: 520-525Crossref PubMed Google Scholar++−1104This study++−WBKehrer-Sawatzki et al.8Kehrer-Sawatzki H Kluwe L Sandig C Kohn M Wimmer K Krammer U Peyrl A Jenne DE Hansmann I Mautner VF High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene.Am J Hum Genet. 2004; 75: 410-423Abstract Full Text Full Text PDF PubMed Scopus (1
Referência(s)