Hillyer Lab News
Hillyer Lab News
Article showing the immunological activity of mosquito NIM genes is published in IBMB
Thursday, November 7, 2013
Mosquitoes, like all other insects, respond to infection by mounting innate immune responses. These immune responses are controlled by several signaling pathways that drive pathogen killing through a variety of effector molecules. Multiple studies have shown that many immune pathways and effector proteins are conserved across insects, although during the course of evolution there have been significant species-specific expansions and reductions in immune gene families.
In the fruit fly, Drosophila melanogaster, various immunity and developmental processes are mediated by members of the Nimrod gene family. These genes encode proteins that contain one or more EGF-like NIM domain. In this article we identify and sequence the members of the Nimrod gene family in the malaria mosquito, Anopheles gambiae, and show that:
1.Draper, nimrod and eater are preferentially produced in hemocytes (immune cells), and peak expression occurs around eclosion.
2.The production of draper, nimrod and eater increases after a bacterial infection.
3.Eater is involved in the killing of Escherichia coli, and Eater and Draper protect mosquitoes from succumbing to a Staphylococcus epidermidis infection.
4.Reduction in eater levels by RNA interference reduces the infection-induced transcriptional upregulation of nitric oxide synthase.
Article citation:
Estévez-Lao, T.Y, and J.F. Hillyer. 2014. Involvement of the Anopheles gambiae Nimrod gene family in mosquito immune responses. Insect Biochemistry and Molecular Biology. 44:12-22.
(Pubmed) (See it in IBMB) (Email me for a pdf copy)
Graphical abstract:
Article abstract:
Insects fight infection using a variety of signaling pathways and immune effector proteins. In Drosophila melanogaster, three members of the Nimrod gene family (draper, nimC1 and eater) bind bacteria, and this binding leads to phagocytosis by hemocytes. The Nimrod gene family has since been identified in other insects, but their function in non-drosophilids remains unknown. The purpose of this study was to identify the members of the Nimrod gene family in the malaria mosquito, Anopheles gambiae, and to assess their role in immunity. We identified and sequenced three members of this gene family, herein named draper, nimrod and eater, which are the orthologs of D. melanogaster draper, nimB2 and eater, respectively. The three genes are preferentially expressed in hemocytes and their peak developmental expression is in pupae and young adults. Infection induces the transcriptional upregulation of all three genes, but the magnitude of this upregulation becomes more attenuated as mosquitoes become older. RNAi-based knockdown of eater, but not draper or nimrod, decreased a mosquito's ability to kill Escherichia coli in the hemocoel. Knockdown of draper, eater, or any combination of Nimrod family genes rendered mosquitoes more likely to die from Staphylococcus epidermidis. Finally, knockdown of Nimrod family genes did not impact mRNA levels of the antimicrobial peptides defensin (def1), cecropin (cecA) or gambicin (gam1), but eater knockdown led to a decrease in mRNA levels of nitric oxide synthase. Together, these data show that members of the A. gambiae Nimrod gene family are positive regulators of the mosquito antibacterial response.
(This post was modified on 12/3/2013 to include the full citation of the article)
“Insect Biochemistry and Molecular Biology publishes original contributions and mini-reviews in the fields of insect biochemistry and insect molecular biology. Main interests areas are neurochemistry, hormone and pheromone biochemistry, enzymes and metabolism, hormone action and gene regulation, gene characterization and structure, pharmacology, immunology and cell and tissue culture.”