The UI-R-CS0 library is a normalized library constructed from the following rat heart tissues: embryonic day 17, embryonic day 19, embryonic day 21, adult day 1, adult day 12, adult day 75, adult day 200. For a detailed description of the library from which this clone was derived, please visit our web site at ratest.eng.uiowa.edu. The subtraction has been previously described in (Bonaldo, Lennon and Soares, Genome Research 6:791-806, 1996)