Genetic_screens_in_haploid_ES_cells___

The project involves the genetic screens in haploid mouse ES cells. Genetic screens in mouse ES cells were budgeted as part of the 5 year plan, but the sequencing money was swept up and consolidated with other aspects, specifically the homozygous mutant ES cell project originally conceived by Bill and I. The original plan was to conduct these screens in Blm-deficient ES cells, which is no longer necessary given the availability of haploid lines. Moreover, the availability of haploid lines provides opportunities to conduct mutagenesis and screens in a different way than originally envisaged with the Blm-deficient ES cells. The principle differences are the use of chemical mutagens, which provide a very high mutagenesis rate compared to insertional mutagens. This will enable deep saturation mutagenesis and the ability to mutagenize areas of the genome that are not active in ES cells [about 40-50% of the genes], facilitating screens in differentiated derivatives. Seven screens are currently envisages in four areas and all of the tasks would be performed at Sanger. The screens include DNA-Mismatch repair [mostly to titrate the mutagenesis], Flu resistance [already conducted in Blm-deficient cells with some hits], Toxin screens [with Gordon/Trevor] and differentiation screens (ESC-EpiSC transition, and neural and hepatic differentiation)