Figure 5.

Models for asymmetric segregation of sister chromatids. Only the template strand of double stranded DNA in sister chromatids prior to mitosis is shown (green and red uninterrupted lines). a. The unidirectional orientation of repetitive DNA at centromeres could result in uneven distribution of epigenetic marks (M) between sister chromatids that foster nucleation or capture of microtubules coming from the “dominant” centrosome. b. Differences in higher-order chromatin structure could alter the elastic properties of (peri-)centric chromatin allowing selection of sister chromatids via microtubules from the “dominant” centrosome. c. Regulation of cell fate predicted by the “Silent Sister” hypothesis. Alternatively, strand-specific methylation [29] or strand-specific transcription of centromeric DNA [30-32] could help establish chromatin asymmetry at sister chromatid centromeres. Centromeric RNA has been implicated in centromere assembly [33] and opposite strands of major satellite DNA are differentially transcribed in specific cell types during murine development [34]. Such chromatin differences could be recognized by factors from asymmetric spindles or favor selective attachment to microtubules via differences in elastic properties (Figure 5b) [35]. Reprinted by permission from Macmillan Publishers Reference [20], copyright 2009.