title: X-chromosome inactivation in healthy females: incidence of excessive lyonization with age and comparison of assays involving DNA methylation and transcript polymorphisms.
abstract: Skewed lyonization in healthy females represents the major disadvantage of X-chromosome-based clonality assays. Because most techniques are based on the difference in DNA methylation between active and inactive X-chromosomes, incomplete DNA digestion may occur, giving an unreliable clonality result. Here, we compare two different techniques carried out in healthy females belonging to three age groups and in a group of patients with essential thrombocythemia. The first technique involved the human androgen receptor gene, the second the transcript analysis of the iduronate-2-sulfatase, P55, and glucose-6-phospate dehydrogenase genes. Results between both techniques were concordant in most cases except in neonates, and the same pattern was observed in all fractions in healthy females. We conclude that: (a) clonality assays involving DNA and RNA polymorphisms are usually concordant except in neonates; (b) appropriate control tissue embryologically related to the sample must be chosen to eliminate excessive lyonization; (c) acquired skewing increases with age, whereas nonrandom lyonization is a rare phenomenon.
authors.affiliation: INSERM U409, Association Claude Bernard, Faculté de Médecine Bichat, Paris. U409@bichat.inserm.fr
authors.forename: N
authors.initials: N
authors.lastname: El Kassar
authors.forename: G
authors.initials: G
authors.lastname: Hetet
authors.forename: J
authors.initials: J
authors.lastname: Brière
authors.forename: B
authors.initials: B
authors.lastname: Grandchamp
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000235:genetics*; D002999:Clone Cells; D004247:DNA / Q000032:analysis; D019175:DNA Methylation; D004303:Dosage Compensation, Genetic; D005260:Female; D006410:Hematopoiesis / Q000235:genetics; D006801:Humans; D007231:Infant, Newborn; D008875:Middle Aged; D016133:Polymerase Chain Reaction / Q000379:methods*; D012150:Polymorphism, Restriction Fragment Length; D012333:RNA, Messenger / Q000032:analysis; D011944:Receptors, Androgen / Q000235:genetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013922:Thrombocytosis / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D012333:RNA, Messenger; D011944:Receptors, Androgen; D004247:DNA