ZFX基因同源序列在黄鳝基因组中的检出及其染色体定位(英文)

Isolation and Chromosomal Localization of ZFX Homologue in Genome of Rice Field Eel (Monopterus albus Zuiew)

以大熊猫锌指蛋白基因Zfx为探针 ,在黄鳝基因组DNA中检测到一条长约 9 5kb的杂交带。依据哺乳类和爬行类动物锌指蛋白基因 (ZFX/Zfc)编码第 7～ 13个锌指结构的DNA序列保守性设计引物 ,在黄鳝基因组DNA中仅扩增到一条 5 12bp的DNA片段。将此片段克隆至载体 pBS中 ,从雌性、雄性个体中分别挑选 4个含有插入片段的白色克隆进行测序。测序结果表明 ,这些克隆中插入片段的核苷酸序列一致。该DNA片段在核苷酸水平上与人类ZFX和ZFY分别具有 88%和 87%同源性 ,但其与美洲鳄鱼Zfc的同源性可达 90 % ,而在氨基酸水平上则分别存在 95 9%、95 9%和 93 5 %的同源性 (170个氨基酸 )。该基因命名为黄鳝锌指蛋白基因Zfa ,并运用FISH将其定位于黄鳝 1号染色体 ,距离着丝粒的相对位置为 6 0 1± 0 38。通过进一步研究证明 ,黄鳝 1号染色体上存在有真兽类哺乳动物X染色质同源的保守片段 ,该保守片段有可能就是哺乳动物X染色体起源和进化的原始物质基础之一。应用哺乳动物X染色体连锁的其他基因在鱼类开展染色体比较定位研究 。

When used as a probe in rice field eel (Monopterus albus Zuiew) genomic Southern blotting hybridization,the giant panda Zfx gene hybridized strongly to a fragment of about 9.5 kb. A 512 bp long DNA fragment has been isolated by polymerase chain reaction from rice field eel genomic DNA using the primers for amplifying zinc finger repeats 7 to 13 of mammalian and reptilian ZFX-related genes. Cloned in pBS,four recombinant plasmids were selected randomly from male and female specimens and sequenced. The nucleotide sequences in these clones were identical and showed 88% and 87% identity to human ZFX and ZFY respectively. But its extent of homology was greater with American alligator Zfc (90%). And the amino acid sequences of the putative protein showed 95.9%,95.9% and 93.5% identity to human ZFX and ZFY and American alligator Zfc respectively. Thus,the cloned sequence encodes a homologue of mammalian ZFX/ZFY and was named Zfa for rice field eel zinc finger domain gene. It appears that the mammalian and reptilian ZFX-related genes evolved from fish ancestors with a considerable degree of conservation. By fluorescence in situ hybridization,the Zfa has been mapped to rice field eel chromosome 1 and at the position of 60.1±0.38 from the centromere. Chromosomal mapping of fish genes related to mammalian X-linked genes might lead to further understanding of the evolution of vertebrate sex chromosomes.