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

Academic Article

Abstract

  • Large NF1 deletions are mediated by nonallelic homologous recombination (NAHR). An in-depth analysis of gene conversion operating in the breakpoint-flanking regions of large NF1 deletions was performed to investigate whether the rate of discontinuous gene conversion during NAHR with crossover is increased, as has been previously noted in NAHR-mediated rearrangements. All 20 germline type-1 NF1 deletions analyzed were mediated by NAHR associated with continuous gene conversion within the breakpoint-flanking regions. Continuous gene conversion was also observed in 31/32 type-2 NF1 deletions investigated. In contrast to the meiotic type-1 NF1 deletions, type-2 NF1 deletions are predominantly of post-zygotic origin. Our findings therefore imply that the mitotic as well as the meiotic NAHR intermediates of large NF1 deletions are processed by long-patch mismatch repair (MMR), thereby ensuring gene conversion tract continuity instead of the discontinuous gene conversion that is characteristic of short-patch repair. However, the single type-2 NF1 deletion not exhibiting continuous gene conversion was processed without MMR, yielding two different deletion-bearing chromosomes, which were distinguishable in terms of their breakpoint positions. Our findings indicate that MMR failure during NAHR, followed by post-meiotic/mitotic segregation, has the potential to give rise to somatic mosaicism in human genomic rearrangements by generating breakpoint heterogeneity. © 2013 WILEY PERIODICALS, INC.
  • Published In

  • Human Mutation  Journal
  • Digital Object Identifier (doi)

    Pubmed Id

  • 1499567
  • Author List

  • Bengesser K; Vogt J; Mussotter T; Mautner VF; Messiaen L; Cooper DN; Kehrer-Sawatzki H
  • Start Page

  • 215
  • End Page

  • 226
  • Volume

  • 35
  • Issue

  • 2