LINKAGE OF THE ATHYMIC NUDE LOCUS WITH THE MYELOPEROXIDASE LOCUS IN THE RAT

In rats of the BUF/Mna strain epithelial thymoma development is regula ted by a single autosomal susceptible gene, Tsr-1. In pre-thymoma stag e, BUF/Mna rats have extremely large thymuses, when compared with thos e of other strains of rats. The large thymus size of this strain is co ntributed by a thymus-enlargement gene, Ten-1. On the other hand, redu ced thymus size and suppression of thymoma development were found in h eterozygous BUF/Mna-rnu/+ rats. Linkage studies between RNU and micros atellite and restriction fragment length polymorphism markers in ([BUF /Mna-rnu/rnu x WKY/NCrj] F1 x WKY/NCrj)- and (WKY/NCrj x [BUF/Mna-mu/r nu x WKY/NCrj] F1)- backcross rats have led to the localization of RNU on chromosome 10. The rat homolog of mouse Mpo (myeloperoxidase) was also assigned to the chromosome 10. The gene order on the chromosome w as MYHSE (myosin heavy chain of embryonic skeletal muscle) -- (1.0 cen timorgan [cM]) -- SHBG (sex hormone-binding globulin) -- (4.0 cM) -- R NU (Rowett rat nude) -- (10.0 cM) -- MPO -- (13.0 cM) -- AEP (anion ex change protein). Conserved linkage of homologous loci mapped to rat ch romosome 10 and mouse chromosome 11 supports the hypothesis that the R NU acid MPO loci are rat homologs of the mouse nu and Mpo loci.