Dlk1-Gtl2 locus carries three differentially methylated regions (DMRs), which are methylated only
on the paternal allele, the Dlk1 DMR in the 3' region
of the Dlk1 gene, the intergenic (IG) DMR located 12 kb upstream of Gtl2 and the Gtl2 DMR
across the promoter and 5' portion of the Gtl2 gene.
Of these, the intergenic (IG) DMR, located 12
kb upstream of Gtl2 is the germline imprint control region (ICR) for this cluster (Lin
SP et al, 2003).
Kota SK et al (2014) found that the
unmethylated maternal allele activates imprinted expression using a mechanism linked to
bidirectional expression of noncoding RNAs (ncRNAs) from the ICR.
The Gtl2 DMR begins
approximately 1.5 kb upstream of
Gtl2, continuing for at least 7.1 kb of Gtl2 (Takada
S et al, 2000) but acquires its methylation postfertilization (Schmidt
JV et al, 2000; Carr
MS et al, 2007).