Frequent gene conversion events between the X and Y homologous chromosomal regions in primates

BMC Evolutionary Biology

Research Article

Hirohisa Hirai¹  Yuriko Hirai¹  Mineyo Iwase²  Yoko Satta³  Naoyuki Takahata⁴ 

[1] Primate Research Institute, Kyoto University, 484-8506, Inuyama, Aichi, Japan;The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (Sokendai), Shonan village, 240-0193, Hayama, Kanagawa, Japan;The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (Sokendai), Shonan village, 240-0193, Hayama, Kanagawa, Japan;Department of Evolutionary Studies of Biosystems, The Graduate University for Advanced Studies (Sokendai), Shonan village, 240-0193, Hayama, Kanagawa, Japan;The Graduate University for Advanced Studies (Sokendai), Shonan village, 240-0193, Hayama, Kanagawa, Japan;

关键词: Rhesus Monkey;    Gene Conversion;    Squirrel Monkey;    World Monkey;    Kallmann Syndrome;   

DOI  :  10.1186/1471-2148-10-225

 received in 2010-01-10, accepted in 2010-07-23,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundMammalian 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.ResultsPhylogenetic 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.ConclusionGene 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.

【 授权许可】

CC BY   
© Iwase et al; licensee BioMed Central Ltd. 2010