Brunner B, Grützner F, Yaspo M L, Ropers H H, Haaf T, Kalscheuer V M
Human Genetics, University Hospital Nijmegen, The Netherlands.
Chromosome Res. 2000;8(6):465-76. doi: 10.1023/a:1009263504671.
We isolated Fugu genomic clones using the human MEST (Mesoderm-Specific Transcript) cDNA as probe. Sequence analysis revealed the presence of MEST and three additional genes which show homology to plant DNBP (DNA-Binding Protein), vertebrate COPG2 (Coat Protein Gamma 2), as well as to human and mouse UCN (Urocortin). Structures of Fugu and human MEST, COPG2 and UCN genes are very similar. Since MEST and COPG2 are neighboring genes on human chromosome 7q32, we can conclude that we identified their orthologs and that linkage of these genes is evolutionarily conserved in vertebrates. Unlike human MEST which underlies isoform-specific imprinting and is methylated in a parent-of-origin-specific fashion, the CpG island of the Fugu ortholog is completely methylated. The translation start of Fugu MEST is identical to the non-imprinted human isoform which is in good agreement with the assumption that genomic imprinting is restricted to mammals. Comparative mapping of these genes by fluorescence in-situ hybridization to metaphase chromosomes of Fugu rubripes and Tetraodon nigroviridis showed clear signals on one of the smallest acrocentric chromosomal pairs, which in Fugu, can be easily classified by its unique triangular shape.
我们以人类中胚层特异性转录物（MEST）cDNA为探针，分离出了河豚基因组克隆。序列分析显示存在MEST以及另外三个基因，它们与植物DNA结合蛋白（DNBP）、脊椎动物COP G2（衣被蛋白γ2）以及人类和小鼠的尿皮质素（UCN）具有同源性。河豚和人类的MEST、COP G2及UCN基因结构非常相似。由于MEST和COP G2是人类7号染色体q32上的相邻基因，我们可以得出结论，我们鉴定出了它们的直系同源基因，并且这些基因的连锁在脊椎动物中是进化保守的。与人类MEST不同，人类MEST是亚型特异性印记的基础，并且以亲本来源特异性方式甲基化，河豚直系同源基因的CpG岛完全甲基化。河豚MEST的翻译起始与非印记的人类亚型相同，这与基因组印记仅限于哺乳动物的假设高度一致。通过荧光原位杂交将这些基因定位到红鳍东方鲀和黑点青鲀中期染色体上，结果显示在最小的近端着丝粒染色体对之一上有清晰信号，在河豚中，该染色体对因其独特的三角形形状很容易识别。
