| Dairy cows play a increasing role in human life, and cows’low fertility has been blocking cows industry development for a long time. In viviparous species, pregnancy process is a natural model of semiallogenic transplantation tolerance existing in the natuaral world.Major histocompatibility complex (MHC) has very important effect on pregnancy establishment and maintainance. Cattle MHC gene is named as BoLA, the bovine leucocyte antigen, located on the No.23chromosome. According to heterologous theory BoLA-Ia is highly polymorphic, and with little difference between parents, pregnancy rejection can be very tiny. In contrast, the expression of BoLA-Ib which has low polymorphism can protect embryo from maternal immun respose, on the basis of this discipline, the lower sharing of BoLA-Ib between copulatory cows, there would be more serious immune rejection.Based on the studies before, some BoLA-I gene alleles significant correlated to pregnancy have been predicted, a BoLA-Ia gene BoLA-A and a BoLA-Ib gene BoLA-NC1were selected among them for this study. The peripheral blood mononuclear cell (PBMC) of dairy cow in peripartum, neonatal ear tissue and semen from the breeding bull were collected for DNA extraction, then amplified the relevent gene sequence and compared the similarity of these two genes’exon2,3in six groups of samples including parental and filial generation cows. The purpose was to understand the displine of the similarity between samples, thus further elucidate the realationship between its similarity and pregnancy maintainance, and discuss the possible influence of the gene similarity on pregnancy.In this study,we found there were general differences in sequences among the parental and calf cows,and the sequences were not exactly the same as posted on NCBI website, it’s obvious that BoLA has high polymorphism not only among different breeds but also in the same group. The result showed that BoLA-A and BoLA-NC1genes were mostly derived from male parent cow(58.33%and55.56%), it suggested that male parent of these two genes has more powerful influence on fetus. the samples we used in this study were from dairy cow,bull semen and fetus in normal pregnancy, the research date showed that there were indeed some differences in exon2and3of BoLA-I between samples, but the differences are relatively small, according the experiment results, It was predicted that for normal and stable pregnancy, the similarity of BoLA-A between parent cows should be above99.75%(Exon2) and99.69%(Exon3), the similarity of BoLA-NC1between parent cows should be below99.57%(Exon2) and99.73%(Exon3). We could not predict the upper and lower limits of sequence similarity between parental cows due to the lack of abnormal pregnancy samples caused by sequence differences.In the same group, the homology between samples of BoLA-A was different from that of BoLA-NC1, but the difference was not significant (P>0.05). The sequence information of Exon2and Exon3in six group were analyzed and single nucleotide mutations were foud in every sample group.we found that there were4SNPs on BoLA-A Exon2,4SNPs on BoLA-A Exon3,10SNPs on BoLA-NC1Exon2and11SNPs on BoLA-NC1Exon3, most mutations resulted in amino acids changes, although some of them were synonymous mutations. In addition, different samples within one group share some common mutation sites. However,we can not summarize all the SNPs in Exon2and3of BoLA-A and BoLA-NC1gene alleles due to the limited number of samples.In this reaearch, the similarity of BoLA-A and BoLA-NC1’ exon2and3were compared in six groups, we found that there were general differences in sequences among parental and filial generation samples, and male parent of these two genes has more powerful influence on fetus. It is suggested that there is a similarity range of these two genes in order to keep normal pregnance. On the other hand,29mutation sites were found in these samples, most of which could result in amino acid changes, and different samples within one group may share some common mutation sites. |
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