Biology subjects

Olson, K. E.

Publications and source records attributed to Olson, K. E..

3 recordsLinked to original sources

bioRxiv2024

Global genomics of Aedes aegypti unveils widespread and novel persistent infectious viruses capable of triggering a small RNA response

The mosquito Aedes aegypti is a prominent vector for arboviruses, but the breadth of mosquito viruses that infects this specie is not fully understood. In the broadest global survey to date of over 200 Ae. aegypti small RNA samples, we detected viral small interfering RNAs (siRNAs) and Piwi interacting RNAs (piRNAs) arising from mosquito viruses. We confirmed that most academic laboratory colonies of Ae. aegypti lack persisting viruses, yet two commercial strains were infected by a novel tombus-like virus. Ae. aegypti from North to South American locations were also teeming with multiple insect viruses, with Anphevirus and a bunyavirus displaying geographical boundaries from the viral small RNA patterns. Asian Ae. aegypti small RNA patterns indicate infections by similar mosquito viruses from the Americas and reveal the first wild example of dengue virus infection generating viral small RNAs. African Ae. aegypti also contained various viral small RNAs including novel viruses only found in these African substrains. Intriguingly, viral long RNA patterns can differ from small RNA patterns, indicative of viral transcripts evading the mosquitoes RNA interference (RNAi) machinery. To determine whether the viruses we discovered via small RNA sequencing were replicating and transmissible, we infected C6/36 and Aag2 cells with Ae. aegypti homogenates. Through blind passaging, we generated cell lines stably infected by these mosquito viruses which then generated abundant viral siRNAs and piRNAs that resemble the native mosquito viral small RNA patterns. This mosquito small RNA genomics approach augments surveillance approaches for emerging infectious diseases.

genomics↗

bioRxiv2021

Genomic insertion locus and Cas9 expression in the germline affect CRISPR/Cas9-based gene drive performance in the yellow fever mosquito Aedes aegypti

The yellow fever mosquito Aedes aegypti is a major vector of arthropod-borne viruses, including dengue, chikungunya, and Zika. A novel approach to mitigate arboviral infections is to generate mosquitoes refractory to infection by overexpressing antiviral effector molecules. Such an approach requires a mechanism to spread these antiviral effectors through a population, for example, by using CRISPR/Cas9-based gene drive (GD) systems. Critical to the design of a single-locus autonomous GD is that the selected genomic locus be amenable to both GD and appropriate expression of the antiviral effector. In our study, we used reverse engineering to target two intergenic genomic loci, which had previously shown to be highly permissive for antiviral effector gene expression, and we further investigated the use of three promoters (nanos, {beta}2-tubulin, or zpg) for Cas9 expression. We then quantified the accrual of insertions or deletions (indels) after single generation crossings, measured maternal effects, and assessed fitness costs associated with the various transgenic lines to model the rate of GD fixation. Overall, MGDrivE modeling suggested that when an autonomous GD is placed into an intergenic locus, the GD system will eventually be blocked by the accrual of GD blocking resistance alleles and ultimately be lost in the population. Moreover, while genomic locus and promoter selection were critically important for the initial establishment of the autonomous GD, it was the fitness of the GD line that most strongly influenced the persistence of the GD in the simulated population. As such, we propose that when autonomous CRISPR/Cas9 based GD systems are anchored in an intergenic locus, they temporarily result in a strong population replacement effect, but as GD-blocking indels accrue, the GD becomes exhausted due to the fixation of CRISPR resistance alleles. Significance statementFor the purpose of population replacement, CRISPR/Cas9 based gene drives (GD) have been developed in Anopheles spp. and split GDs have been developed in Ae. aegypti. In our study, we developed autonomous GD in Ae. aegypti and positioned the drives in intergenic loci ideal for the expression of antiviral effector genes. Our results suggest that when the GD is placed into an intergenic locus, there is rapid introgression of the GD resulting in a transient population replacement followed by loss of the drive as resistance alleles accrue. Fitness of the transgenic lines and maternal deposition of CRISPR/Cas9 components were the major contributing factors affecting the perseverance of the GD in our population models.

synthetic biology↗

bioRxiv2018

Antiviral adaptive immunity and tolerance in the mosquito Aedes aegyti

Mosquitoes spread pathogenic arboviruses while themselves tolerate infection. We here characterize an immunity pathway providing long-term antiviral protection and define how this pathway discriminates between self and non-self. Mosquitoes use viral RNAs to create viral derived cDNAs (vDNAs) central to the antiviral response. vDNA molecules are acquired through a process of reverse-transcription and recombination directed by endogenous retrotransposons. These vDNAs are thought to integrate in the host genome as endogenous viral elements (EVEs). Sequencing of pre-integrated vDNA revealed that the acquisition process exquisitely distinguishes viral from host RNA, providing one layer of self-nonself discrimination. Importantly, we show EVE-derived piRNAs have antiviral activity and are loaded onto Piwi4 to inhibit virus replication. In a second layer of self-non-self discrimination, Piwi4 preferentially loads EVE-derived piRNAs, discriminating against transposon-targeting piRNAs. Our findings define a fundamental virus-specific immunity pathway in mosquitoes that uses EVEs as a potent and specific antiviral transgenerational mechanism.

immunology↗