US-AUSTRALIAN ACADEMIES JOINT WORKSHOP
US-AUSTRALIAN ACADEMIES JOINT WORKSHOP ON VERTEBRATE COMPARATIVE GENOMICS
Beckman Conference Centre, Irvine, California, 23-25 May 2007
Are transposable elements a turn off for the X?
by Matthew Wakefield
Dr Matthew Wakefield received his PhD from La Trobe University in 1999. He has since held research positions at the Research School of Biological Science and the John Curtin School of Medical Research at the Australian National University. He has been a member of the Bioinformatics division at the Walter and Eliza Hall Institute since 2005. His interests include the evolution of conserved non-coding sequences and gene co-expression networks, and the evolution of mammal specific traits.
X chromosome inactivation is the process by which one of the two X chromosomes in female therian mammals is turned off to equalize the amount of gene product to males, who have a single X chromosome. In eutherian mammals X inactivation is a well studied but poorly understood pathway that involves random choice, XIST - a large functional RNA, chromatin modifications, DNA methylation, and nuclear sub-localization. Spreading of the inactivation signal has been hypothesised to use sequences on the X chromosome, including L1 LINE transposable elements, to spread along the X chromosome.
Analysis of the genome sequence of the opossum Monodelphis domestica revealed the absence of L1 LINE transposable element accumulation on the X chromosome. The absence of a significant accumulation indicates that these elements are unlikely to play a role in marsupial X inactivation, suggesting the acquisition of XIST and exaptation of L1 LINEs occured in the eutherian ancestor.
The absence of XIST and L1 LINEs from the marsupial X has been integrated with a model of sex chromosome evolution. This model provides a framework for further study of the evolution of X inactivation using tammar wallaby (Macropus eugenii) sequence and microarray assays of X inactivation status of individual genes.
Contact Details:
The Walter and Eliza Hall Institute of Medical Research
1G Royal Parade, Parkville, Vic, 3050 Australia
Tel: +61 3 9345 2631
Fax: +61 3 9347 0852
Email: wakefield@wehi.edu.au
Web: bioinf.wehi.edu.au
