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RESEARCH ARTICLE
Author
Yoko Satta
Hirohisa Hirai
Yuriko Hirai
Naoyuki Takahata
Description
Background: Mammalian sex-chromosomes originated from a pair of autosomes. A step-wise cessation of recombination is necessary for the proper maintenance of sex-determination and, consequently, generates a four strata structure on the X chromosome. Each stratum shows a specific per-site nucleotide sequence difference (p-distance) between the X and Y chromosomes, depending on the time of recombination arrest. Stratum 4 covers the distal half of the human X chromosome short arm and the p-distance of the stratum is ~10%, on average. However, a 100-kb region, which includes KALX and VCX, in the middle of stratum 4 shows a significantly lower p-distance (1-5%), suggesting frequent sequence exchanges or gene conversions between the X and Y chromosomes in humans. To examine the evolutionary mechanism for this low p-distance region, sequences of a corresponding region including KALX/Y from seven species of non-human primates were analyzed.

Results: Phylogenetic analysis of this low p-distance region in humans and non-human primate species revealed that gene conversion like events have taken place at least ten times after the divergence of New World monkeys and Catarrhini (i.e., Old World monkeys and hominoids). A KALY-converted KALX allele in white-handed gibbons
also suggests a possible recent gene conversion between the X and Y chromosomes. In these primate sequences, the proximal boundary of this low p-distance region is located in a LINE element shared between the X and Y chromosomes, suggesting the involvement of this element in frequent gene conversions. Together with a palindrome on the Y chromosome, a segmental palindrome structure on the X chromosome at the distal boundary near VCX, in humans and chimpanzees, may mediate frequent sequence exchanges between X and Y chromosomes.

Conclusion: Gene conversion events between the X and Y homologous regions have been suggested, mainly in humans. Here, we found frequent gene conversions in the evolutionary course of primates. An insertion of a LINE element at the proximal end of the region may be a cause for these frequent conversions. This gene conversion in humans may also be one of the genetic causes of Kallmann syndrome.
Journal Title
BMC Evolutionary Biology
Volume
10
Issue
225
Start Page
1
End Page
11
ISSN
1471-2148
Published Date
2010
DOI
Publisher
BioMed Central Ltd
Publisher Aalternative
Springer Nature
NII Type
Journal Article
Format
PDF
Resource URL(IsVersionOf)
http://www.biomedcentral.com/1471-2148/10/225
Text Version
出版社版
Gyoseki ID
e29715
OAI-PMH Set
Other