Could genetically-engineered daughterless mice replace the use of poisons in order to keep wild mouse populations at low levels? Rodenticides are arguably more dangerous, less effective, and less humane than introducing daughterless males into a population could be. To determine whether daughterless males could safely replace rodenticides, the public would need to understand the effects of introducing daughterless males into animal populations. In this project, the effectiveness of releasing daughterless males will be studied in laboratory populations of nematodes (worms), which can be genetically engineered more easily than mice, reproduce faster than mice, and can be grown in large laboratory populations. Because the females, males, and daughterless males will be engineered to glow in different colors, the effect of daughterless males can be studied at the molecular and population levels simultaneously. Because nematodes reproduce quickly, the project can study the consequences of introducing daughterless males over many generations. These data will be used along with mathematics to predict the effects of introducing daughterless males into wild mouse populations, analogous to the way that meteorologists use observations to forecast the weather. The predictions will be tested experimentally using genetically engineered daughterless male mice in the laboratory setting. The principles learned in this research could be applied to understanding the impact of genetic engineering on control of any pest population. The glowing worms will be used in museum workshops to educate citizens and invite participants to help determine how local communities can best guide democratic decisions about using genetically-engineered animals to replace rodenticide poisons.
Male-female (dioecious) C. elegans will be generated and then further modified using CRISPR/Cas9 technology to create targeted nuclease activity that selectively prevents development of female embryos. Daughterless males, labelled with green fluorescent protein, will be engineered to block development of red fluorescent protein-labeled female embryos. Normal males in the population will be labelled with blue fluorescent protein. The effects on population dynamics will be studied over many generations by tracking the number of eggs laid in each generation and the frequencies of each fluorescent marker in adults. The effective brood size and the presence of gene flow will be varied. The data will be used to test and refine mathematical models of population suppression. Additionally, daughterless male mice will be generated by using a CRISPR system deposited into zygotes by sperm. The result will be deletion of a DNA sequence required for inactivating the X chromosome, which ought to block XX female embryo development but have no effect on the development of XY males. This project will test the potential of ecological engineering in two unrelated species.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
