Crossover distribution and frequency are regulated by him-5 in Caenorhabditis elegans

Genetics. 2012 Apr;190(4):1251-66. doi: 10.1534/genetics.111.137463. Epub 2012 Jan 20.


Mutations in the him-5 gene in Caenorhabditis elegans strongly reduce the frequency of crossovers on the X chromosome, with lesser effects on the autosomes. him-5 mutants also show a change in crossover distribution on both the X and autosomes. These phenotypes are accompanied by a delayed entry into pachytene and premature desynapsis of the X chromosome. The nondisjunction, progression defects and desynapsis can be rescued by an exogenous source of double strand breaks (DSBs), indicating that the role of HIM-5 is to promote the formation of meiotic DSBs. Molecular cloning of the gene shows that the inferred HIM-5 product is a highly basic protein of 252 amino acids with no clear orthologs in other species, including other Caenorhabditis species. Although him-5 mutants are defective in segregation of the X chromosome, HIM-5 protein localizes preferentially to the autosomes. The mutant phenotypes and localization of him-5 are similar but not identical to the results seen with xnd-1, although unlike xnd-1, him-5 has no apparent effect on the acetylation of histone H2A on lysine 5 (H2AacK5). The localization of HIM-5 to the autosomes depends on the activities of both xnd-1 and him-17 allowing us to begin to establish pathways for the control of crossover distribution and frequency.

Publication types

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

MeSH terms

  • Acetylation
  • Animals
  • Caenorhabditis elegans / cytology
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans / metabolism
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Chromatin / metabolism
  • Chromosome Segregation
  • Cloning, Molecular
  • Crossing Over, Genetic*
  • DNA Breaks, Double-Stranded
  • Gene Expression Regulation
  • Genes, Helminth
  • Hermaphroditic Organisms / genetics
  • Hermaphroditic Organisms / metabolism
  • Histones / metabolism
  • Lysine / genetics
  • Lysine / metabolism
  • Male
  • Pachytene Stage
  • Phenotype
  • Polymorphism, Single Nucleotide
  • Protein Transport
  • RNA Interference
  • Rad51 Recombinase / metabolism
  • Species Specificity
  • X Chromosome / genetics*


  • Caenorhabditis elegans Proteins
  • Chromatin
  • Histones
  • xnd-1 protein, C elegans
  • Rad51 Recombinase
  • rad-51 protein, C elegans
  • Lysine