Butnaru, M.; McKenna, W.; Goswami, S.; Wu-Chuang, A.; Mameli, E.; Wilcox, A.; Quennesson, L.; Kim, A.-R.; Veal, A.; Chen, W.; Verzone, H.; Lane, E. A.; Laukaitis-Yousey, H. J.; Araneo, C.; Singh, N.; Pedra, J.; Hu, Y.; Viswanatha, R.; Perrimon, N.; Mohr, S. E.

The black legged tick, Ixodes scapularis, is a vector of the bacterium that causes Lyme disease and several other illnesses, including anaplasmosis, babesiosis, and tick-borne encephalitis. Although high-quality genome annotations are available for I. scapularis, functional understanding of I. scapularis genes is limited. To address this, we developed a platform for genome-wide CRISPR-Cas9 knockout screening in I. scapularis cells. To evaluate the platform, we performed a screen to identify genes associated with cellular fitness, and screens for resistance to treatment with copper chloride, Antimycin A, or Destruxin A (DA), a cyclic hexadepsipeptide produced by the pathogenic fungus Metarhizium anisopliae. In each case, the screens implicate specific sets of conserved and non-conserved I. scapularis genes in relevant cellular functions, providing the first experimental evidence of function for a large set of I. scapularis genes. Altogether, in this first-of-its-kind effort for the arthropod subclass Acari, we present an unbiased genome-wide CRISPR-Cas9 knockout cell screening platform, related resources, and datasets that will be broadly useful to efficiently uncover cellular functions of I. scapularis genes.