GENETIC DISSECTION OF SUSCEPTIBILITY TO RADIATION-INDUCED APOPTOSIS OF THYMOCYTES AND MAPPING OF RAPOP-1, A NOVEL SUSCEPTIBILITY GENE

Genetic dissection of susceptibility to radiation-induced apoptosis of thymocytes was performed by counting dead cells in histologically pro cessed thymuses after 0.5 Gy of whole-body X-irradiation, using recomb inant congenic (CcS/Dem) strains derived from inbred mouse strains BAL B/cHeA (susceptible) and STS/A (resistant). A high (8/20) number of st rains with lower dead cell scores than BALB/cHeA among CcS/Dem recombi nant congenic strains (RCS), which contain 12.5% of STS/A genome in th e genetic background of BALB/cHeA strain, indicates that the differenc e between BALB/cHeA and STS/A is caused by several genes and that susc eptibility probably requires BALB/cHeA alleles at more than one locus. Similar results were obtained with CXS/Hg recombinant inbred (CXS/Hg) strains. Analysis of Fz hybrids between BALB/cHeA and CcS-7, one of t he CcS/Dem strains that showed lower dead cell scores than BALB/cHeA, demonstrated that a novel gene (Rapop1, radiation-induced apoptosis 1) controlling susceptibility to radiation-induced apoptosis in the thym us is located in the proximal region of mouse chromosome 16. (C) 1995 Academic Press, Inc.