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. 2012 Oct 15;3:214. doi: 10.3389/fgene.2012.00214

Figure 2.

Figure 2

Biallelic insulation at the ICR is not tolerated in development. (A) Introducing strict biallelic insulation to the ICR causes lethality. Substituting the paternal chromosome's (light blue) methylated (black lollipop) ICR of normal mice (middle) with the (ChβGI)2 (Szabó et al., 2002) (orange box) or the (mChβGI)2 (Lee et al., 2010) (turquoise box) has resulted in biallelic insulation (STOP signal). Lethality was observed in the +/(mChβGI)2 but not in the +/(ChβGI)2 genotype. The +/(mChβGI)2 had strict insulation but the +/(ChβGI)2 exhibited leaky insulation. (B) Maternal (pink) duplication of distal chromosome 7 (MatDup.dist7) fetuses that carry biallelic insulation at the ICR, also called imprinting control center 1 (IC1), have 40% body weight and die. The lethality phenotype is rescued by maternal transmission of one copy of the mutant IC1 (x) that lacks CTCF binding and insulator function (Han et al., 2010). The imprinting control center 2 (IC2) is bi-maternal. Correction of biallelic ICR insulation to monoallelic insulation is sufficient to rescue perinatal lethality of the MatDup.dist7 genotype.