Methylation of AR locus does not always reflect X chromosome inactivation state

• Published in: Blood Vol. 119; no. 13; pp. e100 - e109
• Main Authors: Swierczek, Sabina I., Piterkova, Lucie, Jelinek, Jaroslav, Agarwal, Neeraj, Hammoud, Sue, Wilson, Andrew, Hickman, Kimberly, Parker, Charles J., Cairns, Bradley R., Prchal, Josef T.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 29.03.2012; American Society of Hematology
• Subjects: Adult; Case-Control Studies; Chromosomes, Human, X - genetics; Chromosomes, Human, X - metabolism; Clonal Evolution - genetics; DNA Methylation - physiology; Female; Gene Frequency; Genetic Loci; Genotype; Hematopoiesis and Stem Cells; Humans; Janus Kinase 2 - genetics; Male; Myeloproliferative Disorders - genetics; Myeloproliferative Disorders - metabolism; Polymorphism, Genetic; Receptors, Androgen - genetics; Receptors, Androgen - metabolism; Sequence Analysis, DNA - methods; Trinucleotide Repeats - genetics; X Chromosome Inactivation - genetics; X Chromosome Inactivation - physiology
• ISSN: 0006-4971; 1528-0020; 1528-0020
• DOI: 10.1182/blood-2011-11-390351

Clonality can be established by a lack of mosaicism in a female because of random inactivation of either the maternal or paternal X chromosome early in embryogenesis. The methylation status of CpG sites close to the trinucleotide repeats in exon 1 of the human androgen receptor (AR) X chromosome gene assay (HUMARA) has been used to determine clonality. This HUMARA at times indicated clonal hematopoiesis in healthy elderly women, thus precluding its applicability. We used a clonality assay based on quantitative expression of polymorphic X chromosome genes (qTCA) and found no evidence of clonal hematopoiesis in healthy nonanemic elderly persons. We found instances of discordance between HUMARA results and those obtained by pyrosequencing and qTCA methods, as well as by directly quantifying AR gene expression. To determine the basis of this discrepancy we examined the methylation pattern of the AR locus subject to HUMARA. Notably, we found the extent of DNA methylation to be highly variable at the AR gene in granulocytes of persons with discordant results and also in erythroid burst-forming unit colonies but not in those with clonal hematopoiesis. These data provide the molecular basis of incomplete correlation with the pattern of DNA methylation of this X chromosome AR gene locus.