Cell Cycle Kinetics and Sister Chromatid Exchange in Mosaic Turner Syndrome

Abstract

Turner syndrome (TS) is caused by a complete or partial absence of an X or Y chromosome, including chromosomal mosaicism, affecting 1 in 2,500 female live births. Sister chromatid exchange (SCE) is used as a sensitive indicator of spontaneous chromosome instability. Cells from mosaic patients constitute useful material for SCE evaluations as they grow under the influence of the same genetic background and endogenous and exogenous factors. We evaluated proliferation dynamics and SCE frequencies of 45,X and 46,XN cells of 17 mosaic TS patients. In two participants, 45,X cells exhibited a proliferative disadvantage in relation to 46,XN cells after 72h of cultivation. The analysis of mean PI showed significant differences between 45,X and 46,XN lineages; however there were no intraindividual differences. On the other hand, mean SCE frequencies showed no differences between the two lineages, but there were intraindividual differences in 5 patients. The absence of mean SCE frequency differences between 45,X and 46,XN lineages may indicate that both were equally unstable, as more than 70% of the 46,XN lineages had an anomalous karyotype. However, 46,XN had a higher mean PI, suggesting that the amount of cells with a karyotype distinct from 45,X may increase with time in mosaic TS women.