# The male-determining  locus of Culex quinquefasciatus

> **NIH NIH R21** · VIRGINIA POLYTECHNIC INST AND ST UNIV · 2020 · $242,563

## Abstract

Mosquitoes in the Culex genus are principal vectors of encephalitis viruses and lymphatic filariasis worms. Culex
pipiens and C. quinquefasciatus are major vectors of West Nile virus, which is now the leading cause of
mosquito-borne disease in the continental US (https://www.cdc.gov/westnile/index.html). There are concerns
that climate change may cause further increases in West Nile cases. Members of the C. pipiens species complex,
which includes C. quinquefasciatus, C. pipiens, C. molestus and a few other species, show different modes of
evolutionary divergence and exhibit behavioral and physiological differences relevant to their vectorial capacity.
Therefore, the C. pipiens complex are compelling to study from both biomedical and basic science perspectives.
We have a long-standing interest in deciphering the molecular mechanisms by which the male-determining locus
(M locus) controls sex-determination and other aspects of male biology in mosquitoes. We focus on C.
quinquefasciatus in this proposal for both fundamental and translational considerations. As the male-determining
factor (M factor) in C. quinquefasciatus is different from any known M factors in mosquitoes, new insights will be
gleaned into sex-determination governed by a novel master regulator in C. quinquefasciatus. The proposed
research will also lay the foundation for studies into the evolution of homomorphic sex chromosomes and provide
paternally-inherited markers to facilitate investigations into the intriguing evolutionary dynamics of the C. pipiens
complex. From an applied perspective, the proposed research will enable innovative applications to control C.
quinquefasciatus populations through the introduction of a sex bias towards the non-biting males.
By analyzing various RNAseq datasets followed by experimental verifications, we have recently identified two
genes in the M locus including a strong candidate for a novel M factor we named cMf. We have also obtained a
high quality male C. quinquefasciatus genome assembly by separating paternal and maternal long-read
sequences and by Bionano scaffolding. We will pursue two specific aims: 1) systematically characterize the
genetic contents of the M and m loci in C. quinquefasciatus; 2) investigate the function of selected M locus genes
including cMf. This exploratory R21 will produce a systematic annotation of the genetic contents of the M and m
loci and discover the function of the most important M locus genes in C. quinquefasciatus. It will lay the foundation
for future research into 1) the mechanism of action of a novel M factor, 2) the evolution of the homomorphic sex
chromosomes, 3) the functional elements of the m locus, and 4) applications based on sex ratio manipulation or
linkage to the M locus.

## Key facts

- **NIH application ID:** 10071519
- **Project number:** 1R21AI154871-01
- **Recipient organization:** VIRGINIA POLYTECHNIC INST AND ST UNIV
- **Principal Investigator:** Zhijian Jake Tu
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $242,563
- **Award type:** 1
- **Project period:** 2020-06-01 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10071519

## Citation

> US National Institutes of Health, RePORTER application 10071519, The male-determining  locus of Culex quinquefasciatus (1R21AI154871-01). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10071519. Licensed CC0.

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