DNA pooling as a quick method for finding candidate linkages in multigenic trait analysis: an example involving susceptibility to germ cell tumors

A logistical challenge in multigenic trait analysis is typing large numbers of segregants for large numbers of loci with the goal of mapping alleles contributing to the phenotype of interest. We and others showed that DNA pooling, which is also called bulk segregant analysis, is an efficient way to find candidate linkages for monogenic traits such as endogenous proviruses, RAPDs, RFLVs, SSLPs, and mutant genes. The advantage of pooling is that the number of individuals needing to be typed can be reduced dramatically. Here we show that DNA pooling is also effective for finding candidate linkages in multigenic traits such as susceptibility to germ cell tumors in male 129/Sv mice. Given the number of independently segregating loci, mapping germ cell tumor susceptibility alleles is a formidable challenge. Segregation analysis shows that many independently segregating loci with recessive effects control susceptibility to germ cell tumors in 129/Sv mice. Stevens found only one tumor among more than 11,000 males that were surveyed after crossing 129/Sv mice to each of seven other inbred strains and then backcrossing the F sub(1) hybrids to 129/Sv. These results suggest that as many as 13 genes control susceptibility. Neither the map location nor the identity of any of these 129-derived tumor susceptibility alleles has been determined. Presumably, comparable genetic complexity accounts for largely sporadic occurrence of male germ cell tumors in humans. We are taking advantage of a spontaneous mutation called Ter to simplify the genetic analysis.