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. 2018 Dec 24;11(Suppl 2):648.
doi: 10.1186/s13071-018-3211-z.

Effects of stable ectopic expression of the primary sex determination gene Yob in the mosquito Anopheles gambiae

Affiliations

Effects of stable ectopic expression of the primary sex determination gene Yob in the mosquito Anopheles gambiae

Elzbieta Krzywinska et al. Parasit Vectors. .

Abstract

Background: Mosquito-borne diseases, such as malaria, are controlled primarily by suppressing mosquito vector populations using insecticides. The current control programmes are seriously threatened by the emergence and rapid spread of resistance to approved insecticides. Genetic approaches proposed to complement the existing control efforts may be a more sustainable solution to mosquito control. All such approaches would rely on releases of modified male mosquitoes, because released females would contribute to biting and pathogen transmission. However, no sufficiently large-scale methods for sex separation in mosquitoes exist.

Results: Here we exploited the female embryo-killing property of the sex determining gene Yob from the African malaria mosquito, Anopheles gambiae, to evaluate the feasibility of creating transgenic An. gambiae sexing strains with a male-only phenotype. We generated An. gambiae lines with Yob expression, in both sexes, controlled by the vas2 promoter. Penetrance of the female-lethal phenotype was highly dependent on the location of the transgenic construct within the genome. A strong male bias was observed in one of the lines. All the females that survived to adulthood in that line possessed masculinized head appendages and terminal abdominal segments. They did not feed on blood, lacked host-seeking behavior, and thus were effectively sterile. Males, however, were not affected by Yob overexpression.

Conclusions: Our study demonstrates that ectopic expression of Yob results in a recovery of viable, fertile males, and in death, or otherwise strongly deleterious effects, in females. This result shows potential for generation of transgenic sexing strains of Anopheles gambiae with a conditional male-only phenotype.

Keywords: development; genetic sexing; malaria vector; transgenic mosquitoes.

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The authors declare that they have no competing interests.

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Figures

Fig. 1
Fig. 1
Phenotypes of the transgenic An. gambiae lines generated in the study. DsRed expression patterns (a), proportions of the sexes among transgenic individuals (b). Asterisks denote significant male bias: * P < 0.01, ** P < 0.0001; Chi-square test
Fig. 2
Fig. 2
Abdominal termini of An. gambiae pupae, ventral aspect. a Wild-type female. b Wild-type male. c-f Transgenic females. Insets show enlarged genital lobe and cerci area. Black arrows indicate normally developed cerci, long white arrows indicate genital lobe and short white arrows indicate proctiger. Note underdeveloped (c) or missing cerci (d-f), tubercles and projections on the genital lobe (d, f), and an enlarged proctiger extending beyond the genital lobe (c, d, e). In wild-type female pupae (a) proctiger is not visible
Fig. 3
Fig. 3
Details of An. gambiae adult morphology. a Antenna; top to bottom: wild-type female, transgenic female, wild type male. b Maxillary palp; top to bottom: wild-type female, transgenic female, wild type male. Antennae (a) and palps (b) oriented with distal segments on the right. c Abdominal termini; top: transgenic females with a partially developed gonocoxite (black arrow) and a gonostyle (white arrow); bottom left: wild-type female, bottom right: wild-type male (the gonocoxite and gonostyle indicated with arrows as in c)
Fig. 4
Fig. 4
Reverse transcription (RT)-PCR analysis showing altered transcription and pre-mRNA splicing in adult females from the An. gambiae transgenic line 23. a Yob transcript levels in head (H), thorax (T) and abdomen (A) of a transgenic female. b Ribosomal protein S7 transcript levels used as a gel loading control. The same RNA samples were used in (a) and (b). c-f RT-PCR analysis of transcription in three randomly selected transgenic females (Lanes 1-3). c Yob transcript levels. d dsx splicing pattern. e fru splicing pattern. f Ribosomal protein S7 transcript levels used as a gel loading control. The same RNA samples were used in (c-f). In each experiment a whole body RNA sample from a wild-type adult male (M) and female (F) were used for comparison. Note additional, longer Yob transcript isoforms resulting from intron retention in a male; Yob transcripts in transgenic females originate from a cDNA clone, thus lack introns. (-) negative control

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