Expansion and deletion of CTG repeats from human disease genes are determined by the direction of replication in E. coli

Nat Genet. 1995 Jun;10(2):213-8. doi: 10.1038/ng0695-213.


Several human hereditary neurological and neurodegenerative disease genes are associated with the expansion of CTG repeats. Here we show that the frequency of genetic expansions or deletions in Escherichia coli depends on the direction of replication. Large expansions occur predominantly when the CTGs are in the leading strand template rather than the lagging strand. However, deletions are more prominent when the CTGs are in the opposite orientation. Most deletions generated products of defined size classes. Strand slippage coupled with non-classical DNA structures may account for these observations and relate to expansion-deletion mechanisms in eukaryotic chromosomes for disease genes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Sequence
  • DNA Replication*
  • Escherichia coli / genetics*
  • Humans
  • Models, Genetic
  • Models, Molecular
  • Molecular Sequence Data
  • Nervous System Diseases / genetics
  • Plasmids / chemistry
  • Plasmids / genetics
  • Repetitive Sequences, Nucleic Acid*
  • Replication Origin
  • Sequence Deletion
  • Temperature