Fig. 2

The X-Pairing Region (Xpr). Here are summarized data from Augui et al. [10], who used bacterial artificial chromosome (BAC) probes to study interallelic X-chromosome distances at different stages of murine female embryogenesis. The X-inactivation center (XIC), or at least a part of it, is paring in murine female embryo from day 0 on (in undifferentiated ES cells) – green line. This genomic segment contains most of the Slc16a2 gene and was denominated X-pairing region (Xpr). After this segment paired, other parts of this region marked with black lines were pairing. XIC was paired within a critical time window on day 2 in which Xist becomes monoallelically up-regulated, taking place after Xpr aligned. No corresponding study is available for humans; however, homologous human region is depicted for comparison. SLC16A2 gene is highlighted for human and mouse by a green arrow