A Common and Unstable Copy Number Variant Is Associated with Differences in Glo1 Expression and Anxiety-Like Behavior

Abstract

Glyoxalase 1 (Glo1) has been implicated in anxiety-like behavior in mice and in multiple psychiatric diseases in humans. We used mouse Affymetrix exon arrays to detect copy number variants (CNV) among inbred mouse strains and thereby identified a ∼475 kb tandem duplication on chromosome 17 that includes Glo1 (30,174,390–30,651,226 Mb; mouse genome build 36). We developed a PCR-based strategy and used it to detect this duplication in 23 of 71 inbred strains tested, and in various outbred and wild-caught mice. Presence of the duplication is associated with a cis-acting expression QTL for Glo1 (LOD>30) in BXD recombinant inbred strains. However, evidence for an eQTL for Glo1 was not obtained when we analyzed single SNPs or 3-SNP haplotypes in a panel of 27 inbred strains. We conclude that association analysis in the inbred strain panel failed to detect an eQTL because the duplication was present on multiple highly divergent haplotypes. Furthermore, we suggest that non-allelic homologous recombination has led to multiple reversions to the non-duplicated state among inbred strains. We show associations between multiple duplication-containing haplotypes, Glo1 expression and anxiety-like behavior in both inbred strain panels and outbred CD-1 mice. Our findings provide a molecular basis for differential expression of Glo1 and further implicate Glo1 in anxiety-like behavior. More broadly, these results identify problems with commonly employed tests for association in inbred strains when CNVs are present. Finally, these data provide an example of biologically significant phenotypic variability in model organisms that can be attributed to CNVs.

Copy number variation of glyoxalase I

“…One of these was Glo1. The copied region was from 30172971 to 30654177 (approximately 0.5 Mb) [20], of a similar location and size to that reported by Williams et al [19] (Table 1).…”

“…Murine Glo1 CNV was first reported among inbred strains of mice. The CNV was characterized as a 475 kb tandem duplication on chromosome 17 (30174390-30651226) which included complete copies of Glo1 and complete and partial copies of other genes [19].…”

“…In mouse strains, Glo1 CNV was linked to an anxiety phenotype [19], although the link of this through increased Glo1 expression is controversial as an anxiety phenotype has been linked to both increased and decreased Glo1 expression [24,25], contradictory and unexplained findings, as reviewed in [26]. In attempts to link Glo1 metabolically to dysfunctional brain metabolism, MG concentration in brain tissue of mice has been estimated at approximately 170-360 μM [27] and 5 μM MG [28], which appear to be overestimates compared with those of 0.3 and 1.5 μM brain stem/midbrain and cortex when peroxidase and other interferences in the MG assay are blocked [29].…”

Reappraisal of putative glyoxalase 1-deficient mouse and dicarbonyl stress on embryonic stem cellsin vitro

“…The genetic domain duplicated is similar to that found endogenously in some strains of mice [35]. Glo1 duplication is not present in the genetic background of C57BL/6J mice -the strain used in production of the Lexicon Glo1 mutant mice [35]; nor was it present in the 129SvEv Brd ESC line when assessed in 2005 [36]. However, the genome sequence of the 129SvEv Brd ESC cell line assessed later in the Mouse Genomes Project (Sanger Institute) shows Glo1 duplication [37].…”

“…This would explain why hypoxia and MG treatment achieve the same level of induced Glo1 copy number increase individually and together. We propose that hypoxia-activated processes in ESCs under 3% oxygen environment in vivo may contribute to low GLO1 duplication in mouse and human populations [35,50,51].…”