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. 2010 Sep 8;5(9):e12630. doi: 10.1371/journal.pone.0012630

Figure 6. Lethality is caused by strict biallelic insulation at the IC1 in mouse chromosome 7.

Figure 6

(A) Maternal (pink) duplication of distal chromosome 7 (MatDup.dist7) fetuses carry biallelic insulation (STOP signal) at the imprinting control center 1 (IC1) and die. The lethality phenotype is rescued by maternal transmission of one copy of the mutant IC1 that lacks CTCF binding (x) and insulator function [81]. 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. (B) Our present experiments provide the reciprocal argument: introducing strict biallelic insulation to the IC1 causes lethality. By substituting the paternal chromosome's (light blue) methylated (black lollipop) ICR with the unmethylated (ChβGI)2 [44] or the (mChβGI)2 we introduced biallelic insulation into the IC1 and IC2 remained intact. Lethality was observed in the +/(mChβGI)2 but not in the +/(ChβGI)2 genotype 44]. By removing the USF and VEZF1 binding sites from the (ChβGI)2, biallelic insulation has become complete, causing death in the +/(mChβGI)2 genotype.