Figure 1.

Genomic imprinting at the delta-like homolog 1 locus is reset in the subventricular zone. A: Delta-like homolog 1 (Dlk1) is monoallelically expressed from the paternal allele during development. Silencing of the maternal allele takes place in non-neuronal and various neuronal tissues such as the subventricular zone (SVZ) of the lateral ventricle (SVZ) and the medial septum (MS). At the molecular level, maternal silencing results from the absence of DNA methylation at the intergenic, germ line-controlled differentially methylated regions (DMR) (unfilled hexagon), which resides between the Dlk1 and Gtl2 genes and their associated DMRs (unfilled lollipops). Conversely, methylation at the intergenic DMR (filled hexagon), the 3’ end Dlk1 DMR and the Gtl2 DMR (filled lollipops) associates with expression from the paternal allele. The same methylation patterns are present in the SVZ (left scheme) and MS (right scheme) at embryonic ages; B: Dlk1 shows biallelic expression from postnatal day 7 onward towards adulthood in the SVZ, but not in the MS. Hereby, the maternal methylation pattern closely resembles the one on the paternal allele (i.e., methylation at the 3’end Dlk1 DMR, the intergenic DMR, but not the Gtl2 DMR). At opposite, the methylation pattern in the MS is preserved and determines monoallelic Dlk1 expression.