Higher 5-hydroxymethylcytosine identifies immortal DNA strand chromosomes in asymmetrically self-renewing distributed stem cells
Humans have immortality DNA strands.
DSCs, which continually divide asymmetrically in order to replenish mature tissues cells, adopt a particular form of mitotic segregation. The chromosome segregation occurs nonrandomly, not randomly. DSCs cosegregate sister chromosomes using the older template DNA strands that were used in semiconservative replication of DNA during the S phase. The cellular or molecular mechanism responsible for nonrandom segregation is unknown. We report here evidence that mortal chromosomes containing the younger DNA template have a higher cytosine 5hydroxymethylation level than immortal chromosomes. We propose that the asymmetric 5-hydroxymethylation of chromosomes is an important element in a cell mechanism that DSCs use to distinguish older DNA template from younger DNA template strands.
Immortal strands, or chromosomal chromosome DNA strands, are the result of nonrandom sibling chromatidsegregation. This pattern is unique to asymmetrically regenerating distributed stem cells. Through nonrandom segregation immortal DNA strands are the oldest DNA strands within asymmetrically renewing DSCs. The nonrandom segregation may reduce DSC mutation, preserve DSC fate and contribute to DSC ageing. Unknown mechanisms are responsible for the specification and maintenance immortal DNA strands. To discover clues to these mechanisms, we investigated the 5-methylcytosine and 5-hydroxymethylcytosine (5hmC) content on chromosomes in mouse hair follicle DSCs during nonrandom segregation. The 5-methylcytosine level did not differ, but the relative amount of 5hmC in chromosomes with immortal DNA strands was higher than that in mitotic chromosomes that contained younger mortal DNA.