The SNRPN promoter is not required for genomic imprinting of the PraderWilli/Angelman domain in mice

In mice and humans, the locus encoding the gene for small nuclear ribonucle oprotein N (SNRPN/Snrpn), as well as other loci in the region are subject t o genomic imprinting. The SNRPN promoter is embedded in a maternally methyl ated CpG island, is expressed only from the paternal chromosome and lies wi thin an imprinting center that is required for switching to and/or maintena nce of the paternal epigenotype. We show here that a 0.9-kb deletion of exo n 1 of mouse Snrpn did not disrupt imprinting or elicit any obvious phenoty pe. although it did allow the detection of previously unknown upstream exon s. In contrast, a larger, overlapping 4.8-kb deletion caused a partial or m osaic imprinting defect and perinatal lethality when paternally inherited.