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Published online before print
January 14, 2003, 10.1101/gr.390503
LETTER Complex Events in the Evolution of the Human Pseudoautosomal Region 2 (PAR2)1Department of Genetics, La Trobe University, Bundoora, Victoria 3086, Australia; 2Departamento de Biologia, Instituto de Biociências, Universidade de São Paulo, São Paulo-SP, Brasil; 3Comparative Genomics Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia; 4Dipartimento di Anatomia Patologica e di Genetica, Sezione di Genetica, Bari, Italy;5 Institute of Genetics and Biophysics "A. Buzzati Traverso," Naples, Italy. 6University of Glasgow, Department of Medicine and Therapeutics, Western Infirmary, G11 6NT, UK.
The 320-kb human pseudoautosomal region 2 (PAR2) at the tips of the long arms of the X and Y chromosomes is thought to have been duplicated onto the Y chromosome recently in primate evolution. The four genes within PAR2 have been proposed to constitute two zones with different base ratios and transcription, one of which was added recently to the X chromosome. To test this hypothesis, we cloned and mapped PAR2 genes in other species, the lemur, the cat, and a marsupial, the tammar wallaby. None of the human PAR2 genes colocalized with human PAR1 genes in the marsupial genome, confirming that the human PAR1 and PAR2 evolved independently. Of the four PAR2 genes, only SYBL1 was located on the X chromosome in all species, including marsupials, so it was part of the ancient X. HSPRY3 localized to the X in all the eutherians, but not marsupial, so it must have been added to the X 80130 million years ago. CXYorf1 was present on the X in primates and also in mouse, but autosomal in wallaby, suggesting a later addition 70130 million years ago, and IL9R was on the X only in primate, suggesting addition 6070 million years ago. The results therefore demonstrate that at least two independent additions were necessary for PAR2 evolution. The present gene order on the human X also requires two inversions. The complicated evolutionary pathway supports the hypothesis that terminal interchromosomal rearrangements are common in regions unpaired at meiosis. [The sequence data from this study have been submitted to GenBank under accession nos. AF544202, AF544203, AF544204, and AF544205.]
7 These authors contributed equally to this work. E-MAIL fjc4a{at}clinmed.gla.ac.uk; FAX +44 141 211 1763. Article and publication are at http://www.genome.org/cgi/doi/10.1101/gr.390503. Article published online before print in January 2003.
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