title: Quantitative trait locus mapping of genes associated with vacuolation in the adrenal X-zone of the DDD/Sgn inbred mouse.
abstract: BACKGROUND
  Adrenal gland of mice contains a transient zone between the adrenal cortex and the adrenal medulla: the X-zone. There are clear strain differences in terms of X-zone morphology. Nulliparous females of the inbred mouse DDD strain develop adrenal X-zones containing exclusively vacuolated cells, whereas females of the inbred mouse B6 strain develop X-zones containing only non-vacuolated cells. The X-zone vacuolation is a physiologic process associated with the X-zone degeneration and is tightly regulated by genetic factors. Identification of the genetic factors controlling such strain differences should help analyze the X-zone function. In this study, a quantitative trait locus (QTL) analysis for the extent of X-zone vacuolation was performed for two types of F2 female mice: F2Ay mice (F2 mice with the Ay allele) and F2 non-Ay mice (F2 mice without the Ay allele). These were produced by crossing B6 females and DDD.Cg-Ay males. DDD.Cg-Ay is a congenic mouse strain for the Ay allele at the agouti locus and is used for this study because a close association between the X-zone morphology and the agouti locus genotype has been suggested. The Ay allele is dominant and homozygous lethal; therefore, living Ay mice are invariably heterozygotes.
  
  
  RESULTS
  Single QTL scans identified significant QTLs on chromosomes 1, 2, 6, and X for F2 non-Ay mice, and on chromosomes 2, 6, and 12 for F2Ay mice. The QTL on chromosome 2 was considered to be because of the agouti locus, which has been suggested to be associated with X-zone vacuolation. A significant QTL that interacted with the agouti locus was identified on chromosome 8.
  
  
  CONCLUSIONS
  The extent of X-zone vacuolation in DDD females was controlled by multiple genes with complex interactions. The murine X-zone is considered analogous structure to the human fetal zone. Therefore, the results of this study will aid in understanding function of not only of the X-zone but also of the human fetal zone. Identifying the genes responsible for the QTLs will be essential for understanding the molecular basis of X-zone function, which is currently unclear.
authors.affiliation: Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8634, Japan. jsuto@affrc.go.jp
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Suto
mesh_terms: D000302:Adrenal Cortex / Q000378:metabolism* / Q000473:pathology; D000483:Alleles; D000818:Animals; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D010641:Phenotype; D040641:Quantitative Trait Loci