Figure 7. Models of biased sister chromatid segregation patterns in ESCs in vitro and in mouse in vivo.

(Left) Previous studies (Liu et al., 2002; Armakolas and Klar 2006) using mitotic recombination and in combination with restriction-site sensitivity for genotyping in ESC cultures reported that in ESC-derived neuroectodermal lineages no G2-X (recombinant chromosomes segregate away from each other during cell division) events could be observed. In contrast, lineages derived from endodermal stem cells showed exclusively G2-X segregation patterns. Based on these findings, it could be anticipated that in MADM there would be no red and green cells in neural lineages (e.g., in the brain), which was not the case for all MADM chromosomes. (Right) In vivo analysis of the prevalence of G2-X events (red and green cells) in comparison with total number of yellow cells (G2-Z, G1, and G₀ events) for all MADM chromosomes and in several somatic cell lineages revealed a significant bias in the recombinant chromosome and thus sister chromatid segregation patterns. The segregation bias showed marked chromosome specificity that was distinct for different chromosomes in the same cell type in both brain and hematopoietic systems. The segregation bias appears also to be affected by cell type, as the level of bias was distinct for the same chromosome in different cell types.