A novel clonality assay based on transcriptional analysis of the active X chromosome

Abstract

Abstract The clonal origin of malignancy and he‐matopoiesis is a principal tenet of modern biology and medicine. This paper describes a highly specific and sensitive assay for the detection of clonality in cells and cell lineages suitable for studies in a large proportion of females. The specific ligase chain and/ or ligase detection reactions (LCR/LDR) are utilized at a polymorphic glucose‐6‐phosphate dehydrogen‐ase (G‐6‐PD) locus for discrimination of the mRNA transcripts of the active X chromosome. This combination approach circumvents problems encountered with other currently used assays of clonality based either on peptide G‐6‐PD polymorphism or on DNA methylation differences between the active and inactive X chromosomes. The veracity of this assay was verified by analysis of 19 random healthy females as well as by the study of hemopoietic and nonhemopo‐ietic tissues from a patient with clonal hemopoiesis/ polycythemia vera. Furthermore, we demonstrate that the G‐6‐PD locus used in our clonal assay does not display marked differences in methylation between the active and the inactive X chromosomes.