the imprinted expression of the mouse igf2 h19 locus is governed by the differential methylation of the imprinting control region icr which is established initially in germ cells and subsequently maintained in somatic cells depending on its parental origin by grafting a 2 9 kbp h19 icr fragment into a human beta globin yeast artificial chromosome in transgenic mice we previously showed that the icr could recapitulate imprinted methylation and expression at a heterologous locus suggesting that the h19 icr in the beta globin locus contained sufficient information to maintain the methylation mark k tanimoto m shimotsuma h matsuzaki a omori j bungert j d engel and a fukamizu proc natl acad sci usa 102 10250 10255 2005 curiously however the transgenic h19 icr was not methylated in sperm which was distinct from that seen in the endogenous locus here we reevaluated the ability of the h19 icr to mark the parental origin using more rigid criteria in the testis the methylation levels of the solitary 2 9 kbp transgenic icr fragment varied significantly between six transgenic mouse lines however in somatic cells the paternally inherited icr fragment exhibited consistently higher methylation levels at five out of six randomly integrated sites in the mouse genome these results clearly demonstrated that the h19 icr could acquire parent of origin dependent methylation after fertilization independently of the chromosomal integration site or the prerequisite methylation acquisition in male germ cells.