Generation of a polymorphic marker linked to thymoma susceptibility gene of rat 1 by genetically-directed representational difference analysis

BUF/Mna (BUF) is a rat strain susceptible to spontaneous development of thy momas. We have previously shown that the thymoma susceptibility is controll ed principally by a dominant susceptibility gene located on chromosome 7, t hymoma susceptibility gene of rat 1 (Tsr1). To generate genetic markers tig htly linked to Tsr1, we performed genetically directed representational dif ference analysis (GDRDA) with three combinations of the tester and driver D NAs. From 124 \ ACI/NMs x (BUF x ACI/NMs) F-1\ backcross rats, 12 rats with the ACI/BUF genotype in the Tsr1 region (A/B rats) and 13 rats with the AC I/ACI genotype in the region (A/A rats) were selected, and their DNAs were pooled, respectively. Three kinds of tester DNAs, i) inbred BUF, ii (BUF x ACI)F-1, and iii) the pool from the A/B rats, were subtracted by the driver DNA prepared from the pool of the A/A rats. The three combinations yielded one, two, and one polymorphic marker(s), respectively. One marker, D7Ncc28 , was isolated commonly by the three combinations of subtraction, and anoth er marker, D11Ncc12 was isolated only by the second combination. Linkage an alysis demonstrated that D7Ncc28 was located in the 8.3 cM region where Tsr 1 has been mapped. The three combinations of subfraction were shown to be a lmost equally capable of isolating polymorphic markers in a specific chromo somal region.