Analysis of genomic and expressed major histocompatibility class聽Ia and class聽II genes in a hexaploid Lake Tana African 鈥榣arge鈥?barb individual (Barbus intermedius)
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- 作者：CorineP. Kruiswijk ; Trudi Hermsen ; Kazuhiro Fujiki ; Brian Dixon ; HuubF.J. Savelkoul and Ren茅J.M. Stet
- 关键词：MHC class I ; MHC class II ; Gene silencing ; Ploidy ; African large barb
- 刊名：Immunogenetics
- 出版时间：February 2004
- 出版年：2004
- 期刊代码：108_0093-7711
- 类别：bio
- 卷：55
- 期：11
- 页码：770-781
- 数据来源：sp
摘要
Expression of too many co-dominant major histocompatibility complex (MHC) alleles is thought to be detrimental to proper functioning of the immune system. Polyploidy of the genome will increase the number of expressed MHC genes unless they are prone to a silencing mechanism. In polyploid Xenopus species, the number of MHC class I and II genes has been physically reduced, as it does not increase with higher ploidy genomes. In the zebrafish some class IIB loci have been silenced, as only two genomically bona fide loci, DAA/DAB and DEA/DEB, have been described. Earlier studies indicated a reduction in the number of genomic and expressed class II MHC genes in a hexaploid African large barb. This prompted us to study the number of MHC genes present in the genome of an African large barb individual (Barbus intermedius) in relation to those expressed, adopting the following strategy. Full-length cDNA sequences were generated from mRNA and compared with partial genomic class Ia and II sequences generated by PCR using the same primer set. In addition, we performed Southern hybridizations to obtain a verification of the number of class I and IIB genes. Our study revealed three 2-microglobulin, five class Ia, four class IIA, and four class IIB genes at the genomic level, which were shown to be expressed in the hexaploid barb individual. The class Ia and class II data indicate that the ploidy status does not correlate with the presence and expression of these MHC genes.