Figure 1
Colon somatic cell ancestral trees resemble a "big bang", originating from a zygote and progressively growing with aging. All cells eventually relate to each other, and therefore "Y" shaped trees characterize the relationship between any two cells. The last possible common ancestor between widely spaced crypts is around birth, and their ancestral trees must have short trunks and essentially life-long branches. In contrast, more closely spaced crypts may be related by recent crypt fission, yielding ancestral trees with relatively longer trunks and shorter branches. Tree branch lengths may be inferred from methylation pattern drift – methylation at some CpG sites appears to randomly change with aging. Methylation patterns were not significantly different between widely or closely spaced (within the same 1–2 cm2 patch or directly adjacent) crypts, consistent with stable, long-lived adult crypts.