CRISPR-Cas9-Mediated Genetic Screening in Mice with Haploid Embryonic Stem Cells Carrying a Guide RNA Library

• Misexpression of imprinted genes hinders application of haploid mouse ESCs
• The mutation of two paternally imprinted genes improves semi-cloning efficiency
• Genetic manipulation using CRISPR-Cas9 efficiently leads to mutant mice
• Introduction of a CRISPR-Cas9-based library enables mutagenic screening

SummaryMouse androgenetic haploid embryonic stem cells (AG-haESCs) can support full-term development of semi-cloned (SC) embryos upon injection into MII oocytes and thus have potential applications in genetic modifications. However, the very low birth rate of SC pups limits practical use of this approach. Here, we show that AG-haESCs carrying deletions in the DMRs (differentially DNA methylated regions) controlling two paternally repressed imprinted genes, H19 and Gtl2, can efficiently support the generation of SC pups. Genetic manipulation of these DKO-AG-haESCs in vitro using CRISPR-Cas9 can produce SC mice carrying multiple modifications with high efficiency. Moreover, transfection of DKO-AG-haESCs with a constitutively expressed sgRNA library and Cas9 allows functional mutagenic screening. DKO-AG-haESCs are therefore an effective tool for the introduction of organism-wide mutations in mice in a single generation.

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