Whole genome polyploidization has been implicated as a key step in development of cancer and drug resistance. In addition, polyploidization is important in nature for adaptation, speciation, organogenesis, wound healing, and biological scaling. Our understanding of the roles and consequences of polyploidization in multicellular organisms has been limited by the fact that whole genome polyploidy could not be easily induced in laboratory model systems. Nigon was the first to generate Caenorhabditis elegans tetraploid strains, but this method is strenuous and inefficient, yielding only a handful of tetraploid stains in the last 30 years. One way in which tetraploidy arises in nature is by the generation of diploid gametes, which upon fertilization form a tetraploid organism. We have developed an efficient scheme based on the finding that the meiosis-specific cohesin component
rec-8 mutant produces diploid gametes. In
rec-8 mutants asymmetric segregation of chromatids in the second spermatocyte division yields both anucleate and diploid sperm.
rec-8 mutant oocytes fail to extrude the second polar body, giving rise to diploid female gametes. Our method utilizes transient RNAi for
rec-8 to generate tetraploids from any diploid strain, possibly by generating diploid gametes that may give rise to a tetraploid stable strain.
rec-8 RNAi treatment of diploid hermaphrodites of any genotype for two generations occasionally yields Lon animals, which are characteristic of polyploid C. elegans. These Lon animals can give rise to stable tetraploid strains. Using this methodology several complex strains have been generated. These include strains containing balancers, fusion chromosomes, chromosomal inversions and fluorescent markers have been generated. Manipulation of ploidy within a single species will enable us to inquire the role of genome size on development, intracellular and cellular scaling, animal size, cell division, and gene dose. Analysis of some of the tetraploid strains will be presented.