ZFX基因同源序列在黄鳝基因组中的检出及其染色体定位

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 ,将有望促进脊椎动物性染色体进化的深入研究

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

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 amplifng 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 ZFXrespectively 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 ZFX and American alligator Zfc respectively. Thus,the cloned sequence encodes a homologue of mammalian ZFX/ZFX and was named Zfa for rice field eel zinc finger domain gene. Lt appears that the mammalian and reptilian ZFX-related genes evolved fron 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.