Y-CHROMOSOME ANEUPLOIDY, MICRONUCLEI, KINETOCHORES AND AGING IN MEN

This investigation was conducted to determine the relationship between Y chromosome loss and increased micronucleus formation with age, We a lso investigated the status of kinetochore proteins in the micronuclei . Umbilical cord blood samples were obtained from 18 newborn males, an d peripheral blood was obtained from 35 adult males ranging in age fro m 22 to 79 years. Isolated lymphocytes from all 53 donors were culture d and blocked with cytochalasin B. Two thousand binucleate cells per d onor were scored using a modified micronucleus assay to determine the kinetochore status of each micronucleus. This assay showed 23.8% of th e micronuclei to be kinetochore-positive, while 76.2% of the micronucl ei were kinetochore-negative. Cells were then hybridized with a 3.56-k b biotinylated Y chromosome-specific probe. All micronucleate cells we re relocated and their Y probe status was determined. A significant in crease in Y-bearing micronuclei with age was observed. Metaphase cells from the same samples were analyzed for the presence or absence of Y chromosome. The relationship between Y chromosome-positive micronuclei and Y chromosome-negative metaphase cells was highly significant, sug gesting that Y chromosome-deficient metaphase cells result from cells which had previously lost a Y chromosome due to micronucleation. The c ause of micronucleus formation from a lagging Y chromosome appears pro bably to be either a faulty or a diminished amount of kinetochore prot ein.