Comparative mapping identifies the fusion point of an ancient mammalian X-autosomal rearrangement.
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.
Wilcox
S A
SA
School of Genetics and Human Variation, La Trobe University, Melbourne, Victoria, 3083, Australia.
Watson
J M
JM
Spencer
J A
JA
Graves
J A
JA
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