For many years I studied insect cuticular proteins (CPs) as molecular markers of metamorphic stage., now I am interested in the precise role CPs play in constructing insects. We began by annotating the CP genes of Anopheles gambiae, the major vector of malaria. Unexpectedly, we learned that Anopheles devotes over 2% of its protein coding genes to CPs. Shot-gun proteomics analyses established that 82% of the genes we called CPs actually code for proteins found in the cuticle. Some of these are present in the genome as clusters of highly similar genes. Once we had identified the Anopheles CP genes, we turned to learning when and where they are expressed. A comprehensive analysis with quantitative real-time RT-PCR revealed that most mRNAs for CPs are found in brief periods immediately before or after a molt. In situ hybridization revealed where transcripts for specific CPs were located. We learned where in the cuticle secreted proteins are located using secondary antibodies labeled with colloidal gold on EM sections. All of the adult structures we studied have dozens of CPs. So far we have evidence for only 4 CPs being restricted to a single structure, many are present and abundant in all structures.
Annotation has been expanded to other species with the discovery that the largest family, represented by 164 genes in An. gambiae only has 28 members in the honeybee. In addition, we have annotated the proteins with the R&R Consensus in Drosophila (102), and have contributed cuticular protein annotation to genome papers on Apis, Nasonia, the centipede Strigamia and 16 species of Anopheles.
We have analyzed the evolution of these genes, within Anopheles and comparatively, now extending into onychophorans and tardigrades. A collaborator, Stavros Hamodrakas, in Athens, Greece, provided expertise in modelling of CP structures and in construction of databases that facilitate classification of CPs.
Other laboratories have implicated the CPs of Anopheles in insecticide and desiccation resistance, and in being synthesized in response to a blood meal. So our work should serve as the foundation for further studies.
Dr. Willis is no longer training graduate students.
Annotation and expression of insect cuticular protein genes; their roles in construction of cuticle and the the life of insects.
Willis, J.H. 2018 The evolution and metamorphosis of arthropod proteomics and genomics. Ann. Rev. Entomol. 63:1-13.
Willis, J.H. 1986. The paradigm of stage specific gene sets in insect metamorphosis: Time for revision! Arch. Insect Biochem. Physiol. Suppl. 1:47-57.
Willis, J.H., D.L. Cox-Foster (2010) Letter to the Editor Insect metamorphosis via hybridogenesis: An evidentiary rebuttal. J. Insect Physiol. 56:333-335.
Dotson, E.M., A.J. Cornel, J.H. Willis and F.H. Collins. 1998. A family of pupal-specific cuticular protein genes in the mosquito Anopheles gambiae. Insect. Biochem. Molec. Biol. 28: 459-472.
Iconomidou, V.A., J.H. Willis and S.J. Hamodrakas. 2005. Unique features of the structural model of ‘hard’ cuticle proteins: implications for chitin-protein interactions and cross-linking in cuticle. Insect Biochem. Molec. Biol. 35:553-560.
He, N., J.M.C. Botelho, R.J. McNall, V. Belozerov, W.A. Dunn, T. Mize, R. Orlando and J.H. Willis. 2007. Proteomic analysis of cast cuticles from Anopheles gambiae by Tandem Mass Spectrometry. Insect Biochem. Molec. Biol. 37:135-146.
Cornman, R.S., T. Togawa, W.A. Dunn. N. He, A.C. Emmons, J.H. Willis. 2008. Annotation and analysis of a large cuticular protein family with the R&R Consensus in Anopheles gambiae. BMC Genomics 9:22.
Togawa, T., W.A. Dunn, A.C. Emmons, J. Nagao, and J.H. Willis. 2008. Developmental expression patterns of cuticular protein genes with the R&R Consensus from Anopheles gambiae. Insect Biochem. Molec. Biol. 38:508-519.
Cornman, R.S. and J.H. Willis 2009. Annotation and analysis of low-complexity protein families of Anopheles gambiae that are associated with cuticle. Insect Molec. Biol.18:607-622.
Willis, J.H. 2010. Structural cuticular proteins from arthropods: Annotation, nomenclature, and sequence characterization in the genomics era. Insect Biochem. Molec. Biol. 40:189-204.
Ioannidou, Z S., Theodoropoulou, M.C., Papandreou, N.C., Willis, J.H., Hamodrakas, S.J. 2014. CutProtFam-Pred: Detection and classification of putative structural cuticular proteins from sequence alone, based on profile Hidden Markov Models. Insect Biochem. Molec. Biol. 52:51-59.
Zhou, Y., Badgett, M.J., Bowen, J.H., Vannini, L., Orlando, R., Willis, J.H. 2016. Distribution of cuticular proteins in different structures of adult Anopheles gambiae. Insect Biochem. Molec. Biol. 75:45-57.
Vannini, L. and J.H. Willis 2016. Immunolocalization of cuticular proteins in Johnston’s organ and the corneal lens of Anopheles gambiae. Arthropod Structure & Develop. 45:519-535.