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The African malaria vector Anopheles gambiae is polymorphic for alternative arrangements on the left arm of chromosome 2 (2La and 2L+a) that are non-randomly distributed with respect to degree of aridity. Detailed studies on the ecological role of inversion 2La have been hindered by the technical demands of traditional karyotype analysis and by sex- and stage-specific limitations on the availability of polytene chromosomes favorable for analysis. Recent molecular characterization of both inversion breakpoints presented the opportunity to develop a polymerase chain reaction (PCR)-based method for karyotype analysis. Here we report the development of this molecular diagnostic assay and the results of extensive field validation. When tested on 765 An. gambiae specimens sampled across Africa, the molecular approach compared favorably with traditional cytologic methods, correctly scoring > 94% of these specimens. By providing ready access to the 2La karyotype, this tool lays groundwork for future studies of the ecological genomics of this medically important species.
Received August 2, 2006. Accepted for publication November 7, 2006.
Acknowledgments: We thank N. F. Sagnon, C. Costantini, S. Traoré, Y. Touré, L. Mukwaya, and D. Fontenille for collaboration and logistical support and M. Kern, N. Helo, L. Goeddel, S. Zebaze-Kemleu, J-P. Agbor, A. Fofana, and M. Calzetta for technical assistance. For generously sharing samples, the authors thank S. Torr, G. Vale, and the field staff of Rekomitjie Research Station (Zimbabwe); C. Carrara and P. J. Cani (Angola); W. Takken (McCarthy Island); and I. Dia (Senegal). Discussion with F. H. Collins inspired design of the breakpoint-spanning primer.
Financial support: This work was funded by National Institutes of Health Grant AI63508 (to N.J.B.), the UNICEF/UNDP/World Bank/ WHO Special Programme for Research and Training in Tropical Diseases (TDR) Grant A30345 (to L.K.), and MIUR/COFIN 2005 funds (to A.D.T.).
* Address correspondence to Nora J. Besansky, Department of Biological Sciences, 317 Galvin Life Sciences, University of Notre Dame, Notre Dame IN 46556-0369. E-mail: nbesansk{at}nd.edu
Authors addresses: Bradley J. White, Olga Grushko, Karine Mouline, Mamadou Coulibaly, Jonathan K. Kayondo, Igor Sharakhov, and Nora J. Besansky, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, Telephone: 574-631-9321, Fax: 574-631-3996, E-mails: bwhite2{at}nd.edu, cmouline{at}nd.edu, nbesansk{at}nd.edu. Olga Grushko current address, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, E-mail: ogrushko{at}umich.edu. Mamadou Coulibaly current address, Malaria Research and Training Center, Faculté de Médecine, de Pharmacie et dOdonto-Stomatologie, Bamako, Mali, E-mail: coulibaly7{at}gmail.com. Jonathan K. Kayondo current address, Department of Entomology, Uganda Virus Research Institute, Entebbe, Uganda. Igor Sharakhov current address, Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, Telephone: 540-231-7316, Fax: 540-231-9131, E-mail: igor{at}vt.edu. Federica Santolamazza, Marco Pombi, and Alessandra della Torre, Istituto Pasteur-Fondazione Cenci-Bolognetti, Sezione di Parassito-logia, Dipartimento di Scienze di Sanita Pubblica, Universitá di Roma "La Sapienza", Piazzale Aldo Moro 5, 00185 Roma, Italy, Telephone: 39-06-4991-4932, Fax: 39-06-4991-4653, E-mails: federica.santolamazza{at}uniroma1.it, marco.pombi{at}uniroma1.it, ale.dellatorre{at}uniroma1.it. Luna Kamau, Centre for Biotechnology Research and Development, Kenya Medical Research Institute, PO Box 54840, Nairobi, Kenya, E-mail: Lkamau{at}ke.cdc.gov. Cecile Brengues, Institut de Recherche pour le Développement, Unité de Re-cherche R016, Montpellier, France, Telephone: 33-04-6704-1924, Fax: 33-04-6754-2044, E-mail: Cecile.brengues{at}mpl.ird.fr. Wamdaogo Guelbeogo, Centre National de Recherche et Formation sur le Paludisme, 01 BP 2208 Ouagadougou 01, Burkina Faso, E-mail: Moussa_ guelbeogo{at}univ-ouaga.bf. Frederic Simard, Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale, PO Box 288, Yaounde, Cameroon, E-mail: Frederic.Simard{at}ird.fr. Vincenzo Petrarca, Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Universitá di Roma "La Sapienza", Piazzale Aldo Moro 5, 00185 Roma, Italy, E-mail: vincenzo.petrarca{at}uniroma1.it.
Reprint requests: Nora J. Besansky, Department of Biological Sciences, 317 Galvin Life Sciences, University of Notre Dame, Notre Dame IN 46556-0369. E-mail: nbesansk{at}nd.edu.
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