Neurodevelopmental and transcriptomic effects of CRISPR/Cas9-induced somatic mutation in honey bees.

In insects, odorant receptors facilitate olfactory communication and require the functionality of the highly conserved co-receptor gene . Genome editing studies in a few species of ants and moths have revealed that can also have a neurodevelopmental function, in addition to its canonical role in adult olfaction, discovered first in . To extend this analysis, we determined whether mutations also affect the development of the adult brain of the honey bee , an important model system for social behavior and chemical communication. We used CRISPR/Cas9 to knock out and examined anatomical and molecular consequences. To increase efficiency, we coupled embryo microinjection with a laboratory egg collection and rearing system. This new workflow advances genomic engineering technologies in honey bees by overcoming restrictions associated with field studies. We used Sanger sequencing to quickly select individuals with complete knockout for neuroanatomical analyses and later validated and described the mutations with amplicon sequencing. Mutant bees had significantly fewer glomeruli, smaller total volume of all the glomeruli, and higher mean individual glomerulus volume in the antennal lobe compared to wild-type controls. RNA-Sequencing revealed that knockout also caused differential expression of hundreds of genes in the antenna, including genes related to neural development and genes encoding odorant receptors. The expression of other types of chemoreceptor genes was generally unaffected, reflecting specificity of CRISPR activity in this study. These results suggest that neurodevelopmental effects of are related to specific insect life histories.