猪脂肪组织表达序列标签(ESTs)大规模测序及分析

利用大规模DNA序列测定的方法，对猪脂肪组织进行了表达序列标签(Expressed Sequence Tag，EST)序列测定，获得高质量EST共7790个，并对此进行了初步分析。使用STACK-PACK软件进行聚类分析，得到4354个基因聚类，包括3609个单拷贝基因和745个多拷贝基因；将候选基因序列用BlastN与nr库进行比较(e=1e-10)，从4354个候选基因中得到2712个已知基因，其中单基因为1987个，多拷贝基因为725(3694克隆)个；未知功能基因和新EST有2109个克隆。根据BlastN结果，利用基因组文库添加序号(GenBank Accession No．)为索引，构建了猪脂肪组织已知功能基因表达谱。从基因表达谱可以看出，在猪脂肪组织中参与代谢的基因所占比例最高，在某些方面也显示了脂肪组织旺盛的代谢活性。同时发现在猪脂肪组织中主组织相容性抗原(Major Histocompatibility Complex，MHC)或与MHC相关的基因表达丰度很高。其中单拷贝基因181个，多拷贝基因44个，共计257个克隆，占细胞机体防御(cell and organism defense)总数的44．9％。占总已知基因数的5.4％。提取出全部与MHC相关的EST序列(257个克隆)，发现所有EST的部分序列(长约200个碱基)，几乎分布在每一个已知猪BAC的所有编码序列上。据此推测，构成MHC的这些EST序列中，有一段长约200个碱基(200bp)的碱基序列高度保守，MHC基因中每一段编码序列都包含有这一段序列。这些MHC序列虽然在不同的BAC上其蛋白的域不同，但均为高度保守区域，并且都与免疫功能密切相关。猪脂肪中如此大量表达的MHC部分保守序列，由于与免疫功能高度相关，在MHC基因的传递过程中，可以反复复制，并能够稳定遗传。

Sequencing and Analyzing of Expressed Sequence Tags(ESTs)of Pig Fat Tissue

In this paper,the ESTs of pig fat tissue were sequenced and analyzed using the large-scale DNA sequencing method,7 790 high quality ESTs were gained,from which 4 354 genes were obtained using cluster (analysis) with the STACK-PACK software,including 3 609 singlet genes and 745 multicopy genes.The 4 354 candidate genes were compared with BLASTN to the nr library (e=1e-10),of which 2 712 were known genes,containing 1 987 singlet genes and 725 multicopy genes,there are 2 109 unknown genes and new ESTs.Based on the results of BlastN and the index of GenBank Accenssion No.,the known gene expression profile of pig fat were constructed.It showed that the genes participating in metabolism held the highest proportion in the 7 sorts,and in some aspects showed the hearty metabolism activity of fat tissue.257 total reads of the Major Histocompatibility Complex (MHC) genes in the pig fat tissue were found,including 181 singlet genes and 44 multicopy genes.They account for 44.9% of the cell and organism defense,and 5.4% of all known genes,from this we can see that the MHC has a fairly high expression degree.Comparing all ESTs related with MHC (257reads) with known pig BAC we found the partial sequences (approximately 200 bp) of the ESTs distributing to every exon of.We can predict that the ESTs in MHC contain approximately 200 bp highly consistent regions and every exon possesses one of these regions.Although these MHC sequences in different BAC have different protein domains,they are highly consistent and related with immune functions.When the MHC genes transfer to the next generation,they can duplicate repeatly and inherit stably.