Higher frequency of homologous chromosome pairing in adult endothelial cells as compared to neonatal endothelial cells.

Homologous chromosomes are spatially segregated, or antipaired, in neonatal human endothelial cells at metaphase/anaphase, which may help prevent abnormal recombination. However, it is unclear if this antipairing persists in adult endothelial cells. To test whether the antipairing, or one homolog per nuclear hemisphere motif, is conserved in adult endothelial cells, we examined human aortic endothelial cells at metaphase. Using ImmunoFISH and high-resolution confocal microscopy to visualize the chromosomes and centrosomes, we found that small homologous chromosomes 13, 15, 17, 19, 21, 22, and the sex chromosomes, XY, exhibit a loss of spatial segregation in human adult aortic endothelial cells. In addition, fewer adult endothelial cells showed segregation for the larger chromosomes 1, 4, and XX, as compared to neonatal endothelial cells. Notably, we observed a higher frequency of abnormal pairing in both small and large chromosomes in adult aortic endothelial cells as compared to neonatal umbilical vein endothelial cells. These findings suggest that mechanisms governing chromosome antipairing may decline with aortic endothelial cell age.