International Mammalian Genome Society

The 16th International Mouse Genome Conference (2002)


POSTER 111 - ATA3 IS A COMPLEX GENE ON DISTAL CHROMOSOME 15 AND IS REGULATED BY GENOMIC IMPRINTING

R Smith
The Babraham Institute

Dean W L, Kelsey G
The Babraham Institute

To date, over 50 mammalian genes regulated by genomic imprinting have been described.  To identify further imprinted genes, we have performed genome-wide screens for the regions of allele-specific methylation that are characteristic of imprinted loci. One of the genes identified by this technique was Ata3, which encodes a system A amino acid transporter. Ata3 is located on the distal end of chromosome 15; this chromosome was previously thought not to harbour imprinted loci as it gives no overt phenotype when inherited as a uniparental duplication.Sequence analysis of the mouse Ata3 gene indicates that it has a complex structure, with at least three different promoters.  A maternally methylated CpG island is located at one of the promoter regions, indicating that the imprinted expression of Ata3 is promoter-specific.  This CpG island is composed of tandem repeat sequences, which is a feature commonly found at imprinted loci.The transcripts arising from the different promoters encode the same protein but are expressed at different levels in different tissues.  In particular, the paternally expressed transcript from the differentially methylated region is highly expressed in the placenta, where it may be important for the transfer of nutrients from mother to embryo. It is possible that imprinting of the placental Ata3 transcript has evolved as a means by which the paternal allele promotes acquisition of resources by the developing embryo.  We are investigating the role of imprinted Ata3 expression in foetal growth and development by gene targeting approaches.


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