RT Journal
A1 Okamura, Kohji
A1 Hagiwara-Takeuchi, Yuriko
A1 Li, Tao
A1 Vu, Thanh H.
A1 Hirai, Momoki
A1 Hattori, Masahira
A1 Sakaki, Yoshiyuki
A1 Hoffman, Andrew R.
A1 Ito, Takashi
T1 Comparative Genome Analysis of the Mouse Imprinted Gene Impact and Its Nonimprinted Human Homolog IMPACT: Toward the Structural Basis for Species-Specific Imprinting
JF Genome Research 
JO Genome Research 
YR 2000 
FD December 01 
VO 10 
IS 12 
SP 1878 
OP 1889 
DO 10.1101/gr.139200 
UL http://genome.cshlp.org/content/10/12/1878.abstract 
AB Mouse Impact is a paternally expressed gene encoding an evolutionarily conserved protein of unknown function. Here we identified IMPACT, the human homolog of Impact, on chromosome 18q11.2–12.1, a region syntenic to the mouseImpact locus. IMPACT was expressed biallelically in brain and in various tissues from two informative fetuses and in peripheral blood from an informative adult. To reveal the structural basis for the difference in allelic expression between the two species, we elucidated complete genome sequences for both mouse Impact(∼38 kb) and human IMPACT (∼30 kb). Sequence comparison revealed that the two genes share a well-conserved exon–intron organization but bear significantly different CpG islands. The mouse island lies in the first intron and contains characteristic tandem repeats. Furthermore, this island serves as a differentially methylated region (DMR) consisting of a hypermethylated maternal allele and an unmethylated paternal allele. Intriguingly, this intronic island is missing from the nonimprinted human IMPACT, whose sole CpG island spans the first exon, lacks any apparent repeats, and escapes methylation on both chromosomes. These results suggest that the intronic DMR plays a role in the imprinting ofImpact.[The sequence data described in this paper have been submitted to the DDBJ/EMBL/GenBank data library under accession nos. AB026264, AF232228, and AF232229.]