The impact of transgenesis on mosquito fitness: A review

Abstract

Transgenic mosquitoes developed by genetic manipulation, offer a promising strategy for the sustainable and effective control of mosquito-borne diseases. This strategy relies on the mass release of transgenic mosquitoes into the wild, where their transgene is expected to persist in the natural environment, either permanently or transiently, within the mosquito population. In such circumstances, the fitness of transgenic mosquitoes is an important factor in determining their survival in the wild. The impact of transgene expression, insertional mutagenesis, inbreeding depression related to laboratory adaptation, and the hitchhiking effect involved in developing homozygous mosquito lines can all have an effect on the fitness of transgenic mosquitoes. Therefore, real-time estimation of transgene-associated fitness cost is imperative for modeling and planning transgenic mosquito release programs. This can be achieved by directly comparing fitness parameters in individuals homozygous or hemizygous for the transgene and their wild-type counterparts, or by cage invasion experiments to monitor the frequency of the transgenic allele over multiple generations. Recent advancements such as site-specific integration systems and gene drives, provide platforms to address fitness issues in transgenic mosquitoes. More research on the fitness of transgenic individuals is required to develop transgenic mosquitoes with a low fitness cost.

Keywords: disease; fitness; mosquito; transgene; transgenic.

Figure 1

The hitchhiking effect. (A) Chromosomal loci hemizygous for a transgene insert (black X); (B) chromosomal loci homozygous for the transgene insert. Red circles represent the deleterious recessive gene. During transgenesis, the transgene may integrate into the vicinity of a deleterious recessive allele and, when the transgene is made homozygous, any nearby recessive gene will also become homozygous in a process known as the “hitchhiking effect.”.