title: Comparative mapping identifies the fusion point of an ancient mammalian X-autosomal rearrangement.
abstract: Previous comparisons of gene location in the three major groups of mammals (eutherians, marsupials, and monotremes) have suggested that the long arm of the human X represents the ancestral mammalian X chromosome, whereas the short arm represents an autosomal region(s) recently added to the eutherian X chromosome. To identify the fusion point of this ancient X-autosome rearrangement, we have mapped four genes, three of which map near the centromere of the human Xp, in marsupials and in a monotreme. We found that ARAF1, ALAS2, and GATA1 are located on the X chromosome in marsupials, and ALAS2 and GATA1 are also located on the X in the platypus. This implies that the proximal short arm of the human X chromosome, including the centromere, was part of the ancestral mammalian X chromosome. The fusion point between the conserved region and the recently added regions therefore maps to human Xp11.23, although gene order on the human X indicates that there has been some rearrangement of this region.
authors.affiliation: School of Genetics and Human Variation, La Trobe University, Melbourne, Victoria, 3083, Australia.
authors.forename: S A
authors.initials: SA
authors.lastname: Wilcox
authors.forename: J M
authors.initials: JM
authors.lastname: Watson
authors.forename: J A
authors.initials: JA
authors.lastname: Spencer
authors.forename: J A
authors.initials: JA
authors.lastname: Graves
mesh_terms: D000818:Animals; D002503:Centromere / Q000235:genetics; D002874:Chromosome Mapping; D006224:Cricetinae; D003412:Cricetulus / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D017403:In Situ Hybridization; D007614:Macropodidae / Q000235:genetics; D008322:Mammals / Q000235:genetics*; D051379:Mice / Q000235:genetics; D010987:Platypus / Q000235:genetics; D013045:Species Specificity; D014178:Translocation, Genetic; D014960:X Chromosome / Q000235:genetics* / Q000648:ultrastructure