This first case of selective X-inactive-specific-transcript locus duplication suggests a role for gene repression in Turner syndrome and other disorders that affect ovarian function.
Therefore, it is possible that aberrant activation of the marker chromosome, compromising the AR and XIST genes, may modify the Turner syndrome phenotype.
Molecular studies including methylation analysis of 17 differentially methylated regions (DMRs) on the autosomes and the XIST-DMR on the X chromosome and genome-wide microsatellite analysis for 96 autosomal loci and 30 X chromosomal loci revealed that the 46,XX cell lineage was accompanied by maternal uniparental isodisomy for all chromosomes (upid(AC)mat), whereas the 45,X cell lineage was associated with biparentally derived autosomes and a maternally derived X chromosome.
Turner syndrome female with a small ring X chromosome lacking the XIST, an unexpectedly mild phenotype and an atypical association with alopecia universalis.