*Article* **Trypsin-like Inhibitor Domain (TIL)-Harboring Protein Is Essential for** *Aedes aegypti* **Reproduction**

**Chinmay Vijay Tikhe 1,2, Victor Cardoso-Jaime 1,2 , Shengzhang Dong 1,2 , Natalie Rutkowski 1,2 and George Dimopoulos 1,2,\***


**Abstract:** Cysteine-rich trypsin inhibitor-like domain (TIL)-harboring proteins are broadly distributed in nature but remain understudied in vector mosquitoes. Here we have explored the biology of a TIL domain-containing protein of the arbovirus vector *Aedes aegypti*, cysteine-rich venom protein 379 (CRVP379). CRVP379 was previously shown to be essential for dengue virus infection in *Ae. aegypti* mosquitoes. Gene expression analysis showed CRVP379 to be highly expressed in pupal stages, male testes, and female ovaries. CRVP379 expression is also increased in the ovaries at 48 h post-blood feeding. We used CRISPR-Cas9 genome editing to generate two mutant lines of CRVP379 with mutations inside or outside the TIL domain. Female mosquitoes from both mutant lines showed severe defects in their reproductive capability; mutant females also showed differences in their follicular cell morphology. However, the CRVP379 line with a mutation outside the TIL domain did not affect male reproductive performance, suggesting that some CRVP379 residues may have sexually dimorphic functions. In contrast to previous reports, we did not observe a noticeable difference in dengue virus infection between the wild-type and any of the mutant lines. The importance of CRVP379 in *Ae. aegypti* reproductive biology makes it an interesting candidate for the development of *Ae. aegypti* population control methods.

**Keywords:** *Aedes aegypti*; reproduction; trypsin inhibitor; mosquitoes; CRISPR-Cas9; dengue
