Analysis of LMNB1 duplications in autosomal dominant leukodystrophy provides insights into duplication mechanisms and allele-specific expression

Hum Mutat. 2013 Aug;34(8):1160-71. doi: 10.1002/humu.22348. Epub 2013 May 28.

Abstract

Autosomal dominant leukodystrophy (ADLD) is an adult onset demyelinating disorder that is caused by duplications of the lamin B1 (LMNB1) gene. However, as only a few cases have been analyzed in detail, the mechanisms underlying LMNB1 duplications are unclear. We report the detailed molecular analysis of the largest collection of ADLD families studied, to date. We have identified the minimal duplicated region necessary for the disease, defined all the duplication junctions at the nucleotide level and identified the first inverted LMNB1 duplication. We have demonstrated that the duplications are not recurrent; patients with identical duplications share the same haplotype, likely inherited from a common founder and that the duplications originated from intrachromosomal events. The duplication junction sequences indicated that nonhomologous end joining or replication-based mechanisms such fork stalling and template switching or microhomology-mediated break induced repair are likely to be involved. LMNB1 expression was increased in patients' fibroblasts both at mRNA and protein levels and the three LMNB1 alleles in ADLD patients show equal expression, suggesting that regulatory regions are maintained within the rearranged segment. These results have allowed us to elucidate duplication mechanisms and provide insights into allele-specific LMNB1 expression levels.

Keywords: ADLD; FoSTeS; Lamin B1; MMBIR; NHEJ; duplication Alu; leukodystrophy.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Base Sequence
  • Chromosome Breakpoints
  • Comparative Genomic Hybridization
  • DNA / chemistry
  • DNA / genetics
  • Gene Duplication*
  • Humans
  • Lamin Type B / genetics*
  • Lamin Type B / metabolism
  • Molecular Sequence Data
  • Nucleic Acid Conformation
  • Pelizaeus-Merzbacher Disease / genetics*
  • Pelizaeus-Merzbacher Disease / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism

Substances

  • Lamin Type B
  • RNA, Messenger
  • lamin B1
  • DNA

Supplementary concepts

  • Leukodystrophy, Demyelinating, Adult-Onset, Autosomal Dominant