Complex events in the evolution of the human pseudoautosomal region 2 (PAR2).
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 80-130 million years ago. CXYorf1 was present on the X in primates and also in mouse, but autosomal in wallaby, suggesting a later addition 70-130 million years ago, and IL9R was on the X only in primate, suggesting addition 60-70 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.
Charchar
Fadi J
FJ
Department of Genetics, La Trobe University, Bundoora, Victoria 3086, Australia. fjc4a@linmed.gla.ac.uk
Svartman
Marta
M
El-Mogharbel
Nisrine
N
Ventura
Mario
M
Kirby
Patrick
P
Matarazzo
Maria R
MR
Ciccodicola
Alfredo
A
Rocchi
Mariano
M
D'Esposito
Maurizio
M
Graves
Jennifer A Marshall
JA
D000818:Animals; D002415:Cats; D002874:Chromosome Mapping / Q000379:methods; D002877:Chromosomes, Human / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D016906:Interleukin-9; D047908:Intracellular Signaling Peptides and Proteins; D007900:Lemur / Q000235:genetics; D007614:Macropodidae / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics; D050683:R-SNARE Proteins; D018123:Receptors, Interleukin / Q000235:genetics; D053651:Receptors, Interleukin-9; D012689:Sequence Homology, Nucleic Acid; D014960:X Chromosome / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics
C508045:IL9R protein, human; D016906:Interleukin-9; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011506:Proteins; D050683:R-SNARE Proteins; D018123:Receptors, Interleukin; D053651:Receptors, Interleukin-9; C407225:SPRY3 protein, human; C496927:Sybl1 protein, mouse; C121241:VAMP7 protein, human