Extreme clustering of type-1 NF1 deletion breakpoints co-locating with G-quadruplex forming sequences
- 141 Downloads
The breakpoints of type-1 NF1 deletions encompassing 1.4-Mb are located within NF1-REPa and NF1-REPc, which exhibit a complex structure comprising different segmental duplications in direct and inverted orientation. Here, we systematically assessed the proportion of type-1 NF1 deletions caused by nonallelic homologous recombination (NAHR) and those mediated by other mutational mechanisms. To this end, we analyzed 236 unselected type-1 deletions and observed that 179 of them (75.8%) had breakpoints located within the NAHR hotspot PRS2, whereas 39 deletions (16.5%) had breakpoints located within PRS1. Sixteen deletions exhibited breakpoints located outside of these NAHR hotspots but were also mediated by NAHR. Taken together, the breakpoints of 234 (99.2%) of the 236 type-1 NF1 deletions were mediated by NAHR. Thus, NF1-REPa and NF1-REPc are strongly predisposed to recurrent NAHR, the main mechanism underlying type-1 NF1 deletions. We also observed a non-random overlap between type-1 NF1-deletion breakpoints and G-quadruplex forming sequences (GQs) as well as regions flanking PRDM9A binding-sites. These findings imply that GQs and PRDM9A binding-sites contribute to the clustering of type-1 deletion breakpoints. The co-location of both types of sequence was at its highest within PRS2, indicative of their synergistic contribution to the greatly increased NAHR activity within this hotspot.
This work has been funded by the Deutsche Forschungsgemeinschaft (DFG) Grant KE 724/12-2.
Compliance with ethical standards
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
- Bengesser K, Cooper DN, Steinmann K, Kluwe L, Chuzhanova NA, Wimmer K, Tatagiba M, Tinschert S, Mautner VF, Kehrer-Sawatzki H (2010) A novel third type of recurrent NF1 microdeletion mediated by nonallelic homologous recombination between LRRC37B-containing low-copy repeats in 17q11.2. Hum Mutat 31:742–751CrossRefPubMedGoogle Scholar
- Bengesser K, Vogt J, Mussotter T, Mautner VF, Messiaen L, Cooper DN, Kehrer-Sawatzki H (2014) Analysis of crossover breakpoints yields new insights into the nature of the gene conversion events associated with large NF1 deletions mediated by nonallelic homologous recombination. Hum Mutat 35:215–226CrossRefPubMedGoogle Scholar
- De Raedt T, Stephens M, Heyns I, Brems H, Thijs D, Messiaen L, Stephens K, Lazaro C, Wimmer K, Kehrer-Sawatzki H, Vidaud D, Kluwe L, Marynen P, Legius E (2006) Conservation of hotspots for recombination in low-copy repeats associated with the NF1 microdeletion. Nat Genet 38:1419–1423CrossRefPubMedGoogle Scholar
- Dittwald P, Gambin T, Szafranski P, Li J, Amato S, Divon MY, Rodríguez Rojas LX, Elton LE, Scott DA, Schaaf CP, Torres-Martinez W, Stevens AK, Rosenfeld JA, Agadi S, Francis D, Kang SH, Breman A, Lalani SR, Bacino CA, Bi W, Milosavljevic A, Beaudet AL, Patel A, Shaw CA, Lupski JR, Gambin A, Cheung SW, Stankiewicz P (2013) NAHR-mediated copy-number variants in a clinical population: mechanistic insights into both genomic disorders and mendelizing traits. Genome Res 23:1395–1409CrossRefPubMedPubMedCentralGoogle Scholar
- Kehrer-Sawatzki H, Kluwe L, Sandig C, Kohn M, Wimmer K, Krammer U, Peyrl A, Jenne DE, Hansmann I, Mautner VF (2004) 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 75:410–423CrossRefPubMedPubMedCentralGoogle Scholar
- Lopes J, Ravisé N, Vandenberghe A, Palau F, Ionasescu V, Mayer M, Lévy N, Wood N, Tachi N, Bouche P, Latour P, Ruberg M, Brice A, LeGuern E (1998) Fine mapping of de novo CMT1A and HNPP rearrangements within CMT1A-REPs evidences two distinct sex-dependent mechanisms and candidate sequences involved in recombination. Hum Mol Genet 7:141–148CrossRefPubMedGoogle Scholar
- Pasmant E, Sabbagh A, Spurlock G, Laurendeau I, Grillo E, Hamel MJ, Martin L, Barbarot S, Leheup B, Rodriguez D, Lacombe D, Dollfus H, Pasquier L, Isidor B, Ferkal S, Soulier J, Sanson M, Dieux-Coeslier A, Bièche I, Parfait B, Vidaud M, Wolkenstein P, Upadhyaya M, Vidaud D, Members of the NF France Network (2010) NF1 microdeletions in neurofibromatosis type 1: from genotype to phenotype. Hum Mutat 31:E1506–E1518CrossRefPubMedGoogle Scholar
- Roehl AC, Vogt J, Mussotter T, Zickler AN, Spöti H, Högel J, Chuzhanova NA, Wimmer K, Kluwe L, Mautner VF, Cooper DN, Kehrer-Sawatzki H (2010) Intrachromosomal mitotic nonallelic homologous recombination is the major molecular mechanism underlying type-2 NF1 deletions. Hum Mutat 31:1163–1173CrossRefPubMedGoogle Scholar
- Steinmann K, Cooper DN, Kluwe L, Chuzhanova NA, Senger C, Serra E, Lazaro C, Gilaberte M, Wimmer K, Mautner VF, Kehrer-Sawatzki H (2007) 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. Am J Hum Genet 81:1201–1220CrossRefPubMedPubMedCentralGoogle Scholar
- Vogt J, Mussotter T, Bengesser K, Claes K, Högel J, Chuzhanova N, Fu C, van den Ende J, Mautner VF, Cooper DN, Messiaen L, Kehrer-Sawatzki H (2012) Identification of recurrent type-2 NF1 microdeletions reveals a mitotic nonallelic homologous recombination hotspot underlying a human genomic disorder. Hum Mutat 33:1599–1609CrossRefPubMedGoogle Scholar
- Vogt J, Bengesser K, Claes KB, Wimmer K, Mautner VF, van Minkelen R, Legius E, Brems H, Upadhyaya M, Högel J, Lazaro C, Rosenbaum T, Bammert S, Messiaen L, Cooper DN, Kehrer-Sawatzki H (2014) SVA retrotransposon insertion-associated deletion represents a novel mutational mechanism underlying large genomic copy number changes with non-recurrent breakpoints. Genome Biol 15:R80CrossRefPubMedPubMedCentralGoogle Scholar
- Zickler AM, Hampp S, Messiaen L, Bengesser K, Mussotter T, Roehl AC, Wimmer K, Mautner VF, Kluwe L, Upadhyaya M, Pasmant E, Chuzhanova N, Kestler HA, Högel J, Legius E, Claes K, Cooper DN, Kehrer-Sawatzki H (2012) Characterization of the nonallelic homologous recombination hotspot PRS3 associated with type-3 NF1 deletions. Hum Mutat 33:372–383CrossRefPubMedGoogle Scholar