RT asynchrony is lost during differentiation. (A) Distinct cell types were derived from hybrid crosses of M. musculus musculus × M. musculus castaneus. ESC and extraembryonic endoderm stem (XEN) cells were derived from hybrid blastocysts, mouse embryonic fibroblasts (MEF) from hybrid mouse embryos (E12–14), and neural precursor cells (NPC) were differentiated in vitro from hybrid ESC lines. (B) Histograms of RT differences between musculus (129/sv) and castaneus (CAST/Ei) genomes. Labeled in red are the changes higher than the differences between replicates of the same genome. (C) RT asynchronous regions in ESCs become synchronous in differentiated cell types. (D) Two exemplary chromosome regions display the loss of RT asynchrony in differentiated cell types. Two replicates of each sample are shown. Four distinct primary MEFs of opposite gender were obtained from different embryos; RT profiles of female MEFs (MEF XX) and male MEFs (MEF XY) are shown. Data from two independently differentiated NPCs derived from distinct ESC lines (F121-9 and Cas129) are shown.
