To break or not to break: Sex chromosome hemizygosity during meiosis in caenorhabditis

Mike V. Van, Braden J. Larson, Jo Anne Engebrecht

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Meiotic recombination establishes connections between homologous chromosomes to promote segregation. Hemizygous regions of sex chromosomes have no homologous chromosome to recombine with, yet must be transmitted through meiosis. An extreme case of hemizygosity exists in the genus Caenorhabditis, where males have a single X chromosome that completely lacks a homologous partner. To determine whether similar strategies have evolved to accommodate hemizygosity of the X during male meiosis in Caenorhabditis with distinct modes of sexual reproduction, we examined induction and processing of meiotic double strand breaks (DSBs) in androdioecious (hermaphrodite/male) Caenorhabditis elegans and C. briggsae, and gonochoristic (female/male) C. remanei and C. brenneri. Analysis of the recombinase RAD-51 suggests more meiotic DSBs are induced in gonochoristic vs. androdioecious species. However, in late prophase in all species, chromosome pairs are restructured into bivalents around a single axis, suggesting that the holocentric nature of Caenorhabditis chromosomes dictates a single crossover per bivalent regardless of the number of DSBs induced. Interestingly, RAD-51 foci were readily observed on the X chromosome of androdioecious male germ cells, while very few were detected in gonochoristic male germ cells. As in C. elegans, the X chromosome in C. briggsae male germ cells undergoes transient pseudosynapsis and flexibility in DSB repair pathway choice. In contrast, in C. remanei and C. brenneri male germ cells, the X chromosome does not undergo pseudosynapsis and appears refractory to SPO-11-induced breaks. Together our results suggest that distinct strategies have evolved to accommodate sex chromosome hemizygosity during meiosis in closely related Caenorhabditis species.

Original languageEnglish (US)
Pages (from-to)999-1013
Number of pages15
JournalGenetics
Volume204
Issue number3
DOIs
StatePublished - Nov 1 2016

Keywords

  • Double strand breaks (DSBs)
  • Genetics of sex
  • Meiosis
  • RAD-51
  • Sex chromosomes
  • Synapsis

ASJC Scopus subject areas

  • Genetics

Fingerprint Dive into the research topics of 'To break or not to break: Sex chromosome hemizygosity during meiosis in caenorhabditis'. Together they form a unique fingerprint.

  • Cite this