Development of an IGF1R longevity variant mouse line using CRISPR/Cas9 genome editing

An insulin-like growth factor-1 receptor (IGF1R) variant in exon 6 (Arg-407-His) in Ashkenazi Jewish centenarians was previously found to be associated with reduced IGF1R activity. To further study this longevity associated IGF1R variant, we generated a novel mouse line carrying the R407H variant in exon 6 of the Igf1r gene by employing CRISPR/Cas9 genome editing technology. Here, we show that the Igf1r gene can be edited in mouse embryos by zygotic electroporation of Cas9 protein and a single-guide RNAs together with a single stranded oligonucleotide donor containing the desired key nucleotide changes at the Igf1r locus. Sequence analysis of F0 and F1 mice following targeted editing demonstrated the robustness of this approach in mice using CRISPR/Cas9 directed homologous recombination (HDR). Western blot analysis indicates that mice heterozygous for the variant have a significant decrease in IGF1R phosphorylation in various tissues, including skeletal muscle, compared to wildtype. In addition, depletion of IGF1R signaling specifically in skeletal muscle of progeroid Ercc1 ^-/Δ mice resulted in extended health span and median lifespan providing the rationale for long term lifespan studies in Igf1r hR407H variant mice. This mouse line will be a valuable genetic tool to help determine the impact of IGF1R signaling on aging and longevity. The CRISPR editing approach represents a prototype for generating additional longevity associated gene variant mouse lines to study relevance to human exceptional longevity.