Comparative Genomic Sequencing Identifies Novel Tissue-Specific Enhancers and Sequence Elements for Methylation-Sensitive Factors Implicated in Igf2/H19 Imprinting (original) (raw)

  1. Ko Ishihara1,2,3,
  2. Naoya Hatano3,7,
  3. Hiroyasu Furuumi1,3,
  4. Reiko Kato1,3,8,
  5. Toru Iwaki4,
  6. Kiyonori Miura5,9,
  7. Yoshihiro Jinno5,6, and
  8. Hiroyuki Sasaki1,2,3,10
  9. 1Division of Human Genetics, Department of Integrated Genetics, National Institute of Genetics and 2Department of Genetics, Graduate University for Advanced Studies, Mishima, Shizuoka 411-8540, Japan; 3Division of Disease Genes, Institute of Genetic Information, and 4Department of Neuropathology, Neurological Institute, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan; 5Department of Human Genetics, Nagasaki University School of Medicine, Nagasaki 852-8523, Japan; 6Department of Molecular Biology, Ryukyu University School of Medicine, Nishihara, Okinawa 903-0215, Japan

Abstract

A differentially methylated region (DMR) and endoderm-specific enhancers, located upstream and downstream of the mouse H19_gene, respectively, are known to be essential for the reciprocal imprinting of Igf2 and H19. To explain the same imprinting patterns in non-endodermal tissues, additional enhancers have been hypothesized. We determined and compared the sequences of human and mouse H19 over 40 kb and identified 10 evolutionarily conserved downstream segments, 2 of which were coincident with the known enhancers. Reporter assays in transgenic mice showed that 5 of the other 8 segments functioned as enhancers in specific mesodermal and/or ectodermal tissues. We also identified a conserved 39-bp element that appeared repeatedly within the DMR and formed complexes with specific nuclear factors. Binding of one of the factors was inhibited when the target sequence contained methylated CpGs. These complexes may contribute to the presumed boundary function of the unmethylated DMR, which is proposed to insulate maternal_Igf2 from the enhancers. Our results demonstrate that comparative genomic sequencing is highly efficient in identifying regulatory elements.

[The sequence data described in this paper have been submitted to GenBank under accession nos. AF087017 and AF049091.]

Footnotes