Here is an abstract about X chromosome inactivation from this year's AAN meeting:
Challenging the Role of Chromosome X Inactivation in Multiple Sclerosis Pathogenesis
Nicolas Couturier, Pierre-Antoine Gouraud, Pierre Antoinne Gourraud, Céline Rabadeux, Laurie Parmentier, Florence Bucciarelli, Toulouse, France, Isabelle Rebeix, Claire Gout, Jussieu, France, Renato Colamarino, Vichy, France, Florent Borgel, Genoble, France, Serge Mrejen, Paris, France, Philippe Cabre, Martinique, France, Christine Lebrun Frenay, Nice, France, Jacqueline Yaouanq, Rennes, France, Patrick Hautecoeur, Lilles, France, Marc Debouverie, Nancy, France, Gilles Edan, Rennes, France, Michel Clanet, Toulouse, France, Bertrand Fontaine, Paris, France, David Brassat, Toulouse, France
OBJECTIVE: To determine if X chromosome inactivation (XCI) is different between female monozygotic twins discordant for MS.
BACKGROUND: XCI is a phenomenon that occurs in female mammals, whereby one of the two X-chromosomes is randomly inactivated in early embryonic life. Thus females are mosaics for two cell lines that differ in the active X-chromosome. Typically, maternally- and paternally-derived X chromosomes are inactivated at the same frequency and females usually exhibit a random 50:50 ratio of the two cell lines. A skewed X-chromosome inactivation (XCI) is a deviation from this ratio and is arbitrarily defined as a pattern where 80% or more of the cells inactivate the same X-chromosome. Skewed XCI has been reported to occur more frequently in women with scleroderma and autoimmune thyroid disease compared to women without autoimmune diseases.
DESIGN/METHODS: XCI was tested by enzymatic predigestion of genomic DNA with a methylation-sensitive enzyme (Hha1) followed by PCR of the polymorphic CAG repeat of the androgen receptor (AR) gene. This site is methylated on the inactive X-chromosome, so this allele would be amplified by PCR. The active X-chromosome would not be amplified because the sequence is cleaved by Hha1. The relative amounts of the methylated/unmethylated AR alleles were quantitatively determined by migration of the PCR products on a capillary sequencer. We investigated and compared the XCI pattern in DNA from blood cells and epithelial cells from MS patients and from control subjects. This approach allowed us to assess whether MS patients and non-MS persons shared the same degree of XCI.
RESULTS: We found a different XCI intrapair correlation in a population of 20 female monozigotic twin pairs (FMTP) discordant for MS than in 10 FMPT concordant for MS and 30 FMTP with no disease.
CONCLUSIONS/RELEVANCE: We suggest that X-chromosome inactivation may participate in MS pathogenesis in females. Supported by: ARSEP
http://www.abstracts2view.com/aan2009se ... 9L_P08.030