Chromosomal Mapping of Genetic Locus Associated with Thymus‐size Enlargement in BUF/Mna Rats

The thymoma‐prone rat of the BUF/Mna strain is a useful model for human thymoma. In this strain thymoma development is regulated by a single autosomal susceptible gene, Tsr‐1. At pre‐thymoma age, BUF/Mna rats have extremely large thyrauses, when compared to those of other strains of rats. Genetic studies in crosses between BUF/Mna rats with large thymuses and WKY/NCrj rats with small thymuses suggested the presence of a major autosomal gene, Ten‐1, which contributes to thymus enlargement in a backcross population. Linkage studies between Ten‐1 and microsatellite markers in backcross rats of (WKY/NCrj×BUF/Mna)Fl×BUF/Mna have led to the localization of Ten‐1 in chromosome 1. This result may provide an approach to clone Tsr‐1, which could be allelic to Ten‐1.