IMPT1, an imprinted gene similar to polyspecific transporter and multi- drug resistance genes

Human chromosome 11p15.5 and distal mouse chromosome 7 include amegabase-scale chromosomal domain with multiple genes subject to parentalimprinting. Here we describe mouse and human versions of a novel imprintedgene, IMPT1 , which lies between IPL and p57 KIP2 and which encodes apredicted multi-membrane-spanning protein similar to bacterial andeukaryotic polyspecific metabolite transporter and multi- drug resistancepumps. Mouse Impt1 and human IMPT1 mRNAs are highly expressed in tissueswith metabolite transport functions, including liver, kidney, intestine,extra-embryonic membranes and placenta, and there is strongly preferentialexpression of the maternal allele in various mouse tissues at fetal stages.In post-natal tissues there is persistent expression, but the allelic biasattenuates. An allelic expression bias is also observed in human fetal andpost-natal tissues, but there is significant interindividual variation andrare somatic allele switching. The fact that Impt1 is relatively repressedon the paternal allele, together with data from other imprinted genes,allows a statistical conclusion that the primary effect of human chromosome11p15.5/mouse distal chromosome 7 imprinting is domain-wide relativerepression of genes on the paternal homolog. Dosage regulation of themetabolite transporter gene(s) by imprinting might regulate placental andfetal growth.