Marklund L, Jeon J T, Andersson L
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala Biomedical Centre, S-751 24 Uppsala, Sweden.
Genome Res. 1998 Apr;8(4):399-403. doi: 10.1101/gr.8.4.399.
Somatic cell hybrid (SCH) panels and radiation hybrid (RH) panels are powerful resources for comparative gene mapping because gene assignments are made without the detection of genetic polymorphism as needed for linkage mapping. A frequently encountered problem, however, is that the gene specific primers may amplify homologous PCR products of equal length from the donor and recipient species of the panel. Here, we describe a simple solution to this problem in which we utilize the formation of interspecies heteroduplexes that can be easily distinguished from the corresponding homoduplexes by native polyacrylamide gel electrophoresis. We denote these DNA-DNA interspecies hybrids, xenoduplexes (xeno = Gr. Xenos, foreigner). A merit of the method is that the formation of xenoduplexes strongly suggests that the PCR products from the two species represent homologous sequences. The method is thus particularly useful for comparative gene mapping when the PCR primers have been designed by use of sequence information from other species. In this study we have successfully used xenoduplex analysis and a pig-rodent SCH panel to map seven porcine genes (ACADM, AT3, HOXD, IL8RB, LEPR, PAX8, PKLR) for which no previous sequence information was available. The assignment of the leptin receptor gene (LEPR) to pig chromosome 6q32-35 excluded LEPR as a candidate gene for a QTL on pig chromosome 4 with a major effect on fatness.
体细胞杂种（SCH）板和辐射杂种（RH）板是用于比较基因定位的强大资源，因为基因定位无需像连锁定位那样检测遗传多态性。然而，一个经常遇到的问题是，基因特异性引物可能会从板的供体和受体物种中扩增出长度相等的同源PCR产物。在这里，我们描述了一个解决这个问题的简单方法，即利用种间异源双链体的形成，通过天然聚丙烯酰胺凝胶电泳可以很容易地将其与相应的同源双链体区分开来。我们将这些DNA-DNA种间杂种称为异源双链体（xeno = 希腊语Xenos，外国人）。该方法的一个优点是，异源双链体的形成强烈表明来自两个物种的PCR产物代表同源序列。因此，当PCR引物是根据其他物种的序列信息设计时，该方法对于比较基因定位特别有用。在本研究中，我们成功地使用异源双链体分析和猪-啮齿动物SCH板对七个猪基因（ACADM、AT3、HOXD、IL8RB、LEPR、PAX8、PKLR）进行了定位，此前这些基因没有可用的序列信息。将瘦素受体基因（LEPR）定位到猪6号染色体6q32-35排除了LEPR作为对猪4号染色体上影响脂肪含量的一个主要数量性状位点（QTL）的候选基因。
