The 3rd International Workshop on Advanced Genomics
Pacifico Yokohama, Yokohama, Japan
November 13, 2000
Poster presentation

Allelic methylation analysis of the mouse imprinted gene Impact by its polymorphisms
Kohji Okamura1, Yuriko Hagiwara-Takeuchi1, Masahira Hattori2, Yoshiyuki Sakaki1,2, and Takashi Ito1,3
1Hum. Genome Ctr., Inst. Med. Sci., Univ. Tokyo, Japan, 2Hum. Genome Res. Gr., RIKEN Genomic Sci. Ctr., Japan, 3Dept. Mol. Oncology, Cancer Res. Inst., Kanazawa Univ., Japan
The mouse Impact is a paternally expressed gene, but its human homolog IMPACT is expressed biallelically. This species-specific imprinting led us to perform a comparative genome analysis, which revealed well-conserved exon-intron organization and marked difference in CpG island. The mouse CpG island lies in the first intron and has many intriguing tandem repeats, which are often associated with imprinted genes. We identified a length polymorphism and some single nucleotide polymorphisms (SNPs) in and near the islands between two mouse strains. A PCR assay with methylation-sensitive endonucleases was used to analyze the F1 hybrids of the two strains to show that only maternal allele is hypermethylated in the island and that this differentially methylation extends to the promoter region but not to the whole gene. These results suggest that the intronic CpG island plays a crucial role in the imprinting of the Impact.