Analysis of CpG islands of trophoblast giant cells by restriction landmark genomic scanning

Jun Ohgane, Jun Ichi Aikawa, Atsuo Ogura, Naka Hattori, Tomoya Ogawa, Kunio Shiota*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

62 Citations (Scopus)


Rat trophoblast giant cells each contain at least 100 times more genomic DNA per nucleus than diploid cells. This unusual phenomenon appears to be of interest in relation to the molecular mechanism of cell differentiation and gene expression in the placenta. In the present study, we analyzed the CpG islands of trophoblast giant cells by restriction landmark genomic scanning (RLGS) using the methylation-sensitive landmark enzymes, Not I and Bss HII. More than 1,000 and 1,900 spots were detected by RLGS using Not I and Bss HII, respectively, in the placental junctional zone, where more than 90% of genomic DNA is present in the cells with higher DNA content. Of these, 97% (1,009 spots) and 99% (1,911 spots) of the spots found in the junctional zone showed an identical pattern and identical intensity with those of diploid cell controls, for which genomic DNA was extracted from the labyrinth zone and maternal kidney. Therefore, the giant cells are basically polyploid. More importantly, 24 tissue-specific spots were detected by RLGS using Not I. Subsequent cloning and sequencing of four typical spots of the genomic DNA confirmed that these DNA fragments contained abundant CpG dinucleotides and showed characteristics of CpG islands. Of these 24 spots, there were ten spots specific far the placenta, and three of them were specific for the junctional zone, indicating that methylation status of CpG islands in the placental tissue differed between the junctional zone and labyrinth zone. These results suggest that multiple rounds of endoreduplication and modification of CpG islands by cytosine methylation occur during the differentiation process of giant cells.

Original languageEnglish
Pages (from-to)132-140
Number of pages9
JournalDevelopmental Genetics
Issue number2
Publication statusPublished - 1998
Externally publishedYes


  • CpG island
  • DNA methylation
  • Giant cell
  • Restriction landmark genomic scanning (RLGS)
  • Trophoblast

ASJC Scopus subject areas

  • Developmental Biology
  • Cell Biology
  • Genetics


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