Related Experiment Video
Updated: Nov 4, 2025
Preparing and Injecting Embryos of Culex Mosquitoes to Generate Null Mutations using CRISPR/Cas9
Published on: September 10, 2020
The urban-adapted underground mosquito Culex pipiens form molestus maintains exogenously influenceable circadian
Natalie R Epstein1, Kevin Saez1, Asya Polat1
1Department of Biology, Montclair State University, 1 Normal Avenue, Montclair, NJ 07043, USA.
Abstract:
Genes known to affect circadian rhythms (i.e. 'clock genes') also influence the photoperiodic induction of overwintering reproductive diapause in the northern house mosquito, Culex pipiens f. pipiens. This suggests that molecular changes in one or more clock genes could contribute to the inability to diapause in a second form of this mosquito, Culex pipiens f. molestus. Temperate populations of Cx. pipiens f. molestus inhabit underground locations generally devoid of predictable photoperiods. For this reason, there could be limited fitness consequences if the hypothesized molecular changes to its clock genes also eliminated this mosquito's ability to regulate circadian rhythms in response to photoperiod variation. Here, we demonstrate that in contrast to this prediction, underground derived Cx. pipiens f. molestus retain exogenously influenceable circadian rhythms. Nonetheless, our genetic analyses indicate that the gene Helicase domino (dom) has a nine-nucleotide, in-frame deletion specific to Cx. pipiens f. molestus. Previous work has shown that splice variants in this gene differentially influence circadian behavior in Drosophila melanogaster. We also find derived, non-synonymous single nucleotide polymorphisms (SNPs) in eight genes that may also affect circadian rhythms and/or diapause induction in Cx. pipiens f. molestus. Finally, four putative circadian genes were found to have no quantifiable expression during any examined life stage, suggesting potential regulatory effects. Collectively, our findings indicate that the distinct, but molecularly interconnected life-history traits of diapause induction and circadian rhythms are decoupled in Cx. pipiens f. molestus and suggest this taxon may be a valuable tool for exploring exogenously influenced phenotypes in mosquitoes more broadly.
Insights
Molecular changes in clock genes may explain why the Culex pipiens f. molestus mosquito cannot diapause. Despite living underground, these mosquitoes retain circadian rhythms, but genetic analysis reveals specific gene alterations, suggesting a decoupling of diapause and circadian regulation.
Area of Science:
- Genetics
- Chronobiology
- Insect Physiology
Background:
- Circadian rhythms, regulated by 'clock genes', influence seasonal adaptations like overwintering reproductive diapause in mosquitoes.
- Culex pipiens f. molestus, a form of the northern house mosquito, inhabits environments lacking predictable light cues, potentially impacting its diapause ability.
- It was hypothesized that molecular changes in clock genes might underlie the reduced diapause capacity in Cx. pipiens f. molestus.
Purpose of the Study:
- To investigate the relationship between circadian rhythms and diapause induction in Culex pipiens f. molestus.
- To identify genetic factors, particularly in clock genes, that may contribute to the distinct life-history traits of this mosquito form.
- To determine if underground-derived Cx. pipiens f. molestus retain functional circadian rhythms despite their habitat.
Main Methods:
- Genetic analysis to identify mutations and single nucleotide polymorphisms (SNPs) in clock genes.
- Gene expression analysis to quantify the presence of putative circadian genes across different life stages.
- Phenotypic assessment to confirm the presence of exogenously influenceable circadian rhythms.
Main Results:
- Underground-derived Cx. pipiens f. molestus populations exhibit functional, exogenously influenceable circadian rhythms.
- A specific nine-nucleotide deletion in the Helicase domino (dom) gene was identified exclusively in Cx. pipiens f. molestus.
- Derived non-synonymous SNPs were found in eight other genes potentially affecting circadian rhythms or diapause, and four circadian genes showed no detectable expression.
Conclusions:
- Circadian rhythms and diapause induction appear to be molecularly decoupled in Cx. pipiens f. molestus.
- Specific genetic alterations, including a unique deletion in the dom gene, are associated with this decoupling.
- Cx. pipiens f. molestus serves as a model for studying exogenously influenced phenotypes and the genetic basis of life-history trait variation in mosquitoes.
Related Concept Videos
02:19Circadian Rhythms and Gene Regulation
00:58Symbiosis