RT Journal
A1 Grützner, Frank
A1 Crollius, Hugues Roest
A1 Lütjens, Götz
A1 Jaillon, Olivier
A1 Weissenbach, Jean
A1 Ropers, Hans-Hilger
A1 Haaf, Thomas
T1 Four-Hundred Million Years of Conserved Synteny of Human Xp and Xq Genes on Three Tetraodon Chromosomes
JF Genome Research 
JO Genome Research 
YR 2002 
FD September 01 
VO 12 
IS 9 
SP 1316 
OP 1322 
DO 10.1101/gr.222402 
UL http://genome.cshlp.org/content/12/9/1316.abstract 
AB The freshwater pufferfish Tetraodon nigroviridis (TNI) has become highly attractive as a compact reference vertebrate genome for gene finding and validation. We have mapped genes, which are more or less evenly spaced on the human chromosomes 9 and X, onTetraodon chromosomes using fluorescence in situ hybridization (FISH), to establish syntenic relationships between Tetraodonand other key vertebrate genomes. PufferFISH revealed that the human X is an orthologous mosaic of three Tetraodon chromosomes. More than 350 million years ago, an ancestral vertebrate autosome shared orthologous Xp and Xq genes with Tetraodon chromosomes 1 and 7. The shuffled order of Xp and Xq orthologs on their syntenic Tetraodon chromosomes can be explained by the prevalence of evolutionary inversions. The Tetraodon 2 orthologous genes are clustered in human Xp11 and represent a recent addition to the eutherian X sex chromosome. The human chromosome 9 and the avian Z sex chromosome show a much lower degree of synteny conservation in the pufferfish than the human X chromosome. We propose that a special selection process during vertebrate evolution has shaped a highly conserved array(s) of X-linked genes long before the X was used as a mammalian sex chromosome and many X chromosomal genes were recruited for reproduction and/or the development of cognitive abilities.[Sequence data reported in this paper have been deposited in GenBank and assigned the following accession no:AJ308098.]