Identification of genetic and epigenetic similarities of SPHK1/Sphk1 in mammals
2004
Imamura, T. (Tokyo Univ. (Japan)) | Miyauchi Senda, N. | Tanaka, S. | Shiota, K.
In normal tissues, methylation of CpG islands is generally accepted to be limited to the inactive X-chromosome and imprinting clusters. Gene Sphkl has shown complex organization, indicated by multiple alternative splicing and tissue-dependent DNA methylation within the limited area (T-DMR) of the CpG island in the rat. Comparisons among human, mouse and rat SPHKL/Sphkl genomic DNA revealed five coding exons and association of a CpG island at the 5' end in common. We also found two novel subtypes, for a total of eight mRNA subtypes generated through selective usage of untranslated first exons. A 38-bp region at the 5'-end of T.DMR is highly conserved. This restricted area is specifically hypomethylated in the brain. Here, we examine the complex genetic/epigenetic features of the SPHKI/Sphkl CpG island, and suggest that the T-DMR is the core target for tissue-dependent CpG island methylation.
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