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

Abstract

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 -/∆ 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.

Targeting IGF1R signaling for brain aging and Alzheimer’s disease

“…Individuals carrying two specific variants, A37T and R407H, had a significant reduction in IGF1R protein and its phosphorylation levels. Based on these observations, we used CRISPR technology to develop a mouse model with a targeted replacement of mouse IGF1R with the equivalent of the human R407H (IGF1R R407H ) variant [10]. The objective was to establish a Aging Pathobiology and Therapeutics 2022; 4(4): 129-131 130 COMMENTARY precision animal model that could help provide definitive answers to the role of IGF1R signaling in aging, including age-associated conditions such as cardiac aging and neurodegeneration.…”

“…Based on these observations, we used CRISPR technology to develop a mouse model with a targeted replacement of mouse IGF1R with the equivalent of the human R407H (IGF1R R407H ) variant [ 10 ]. The objective was to establish a precision animal model that could help provide definitive answers to the role of IGF1R signaling in aging, including age-associated conditions such as cardiac aging and neurodegeneration.…”