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[edit] Anopheles gambiae
Anopheles gambiae, refers to a complex of morphologically indistinguishable mosquitoes in the genus Anopheles, which contains the most important vectors of malaria in Sub-Saharan Africa.
[edit] Source of the PEST strain used in sequencing
The Anopheles gambiae PEST strain was chosen for genome sequencing [1] because it had both a fixed, standard chromosomal arrangement [2] and a sex-linked pink eye mutation that could readily be used as an indicator of cross-colony contamination [3]. The pink eye mutation originated in a colony called A. gambiae LPE established in 1951 at the London School of Hygiene and Tropical Medicine from mosquitoes collected in Lagos, Nigeria. In 1986, this mutation was introduced into a colony of A. gambiae from western Kenya by crossing males of the LPE strain with female offspring of wild caught Kenyan A. gambiae (the Savanna form), selecting males from the F2 of this cross and then crossing them again with additional female offspring of wild caught Kenyan A. gambiae. From the F2 offspring of this second outcross to Kenyan mosquitoes, a strain was selected that was fixed for pink eye. This outcrossing scheme was repeated one more time in 1987 producing a pink eye strain with a genetic composition largely constituted of the western Kenya Savanna cytogenetic form. In each of these crosses, several hundred female offspring of at least 20 wild caught mosquitoes were used in the cross. This strain, designated A. gambiae PE, was polymorphic for the inversions 2La (32%) and 2Rbc (19%). The 2Rbc inversion is characteristic of Mopti, indicating that the original LPE strain from Nigeria was the Mopti form. This inversion was apparently balanced by the uninverted form, because no 2Rbc/bc individuals were detected in the colony. Mukabayire and Besansky [2] selected from this PE strain a set of 9 families whose female parent and at least 20 female offspring were fixed for the standard chromosome karyotype. The progeny of these nine families were pooled to form the A. gambiae PEST strain (Pink Eye STandard). This strain clearly had some Mopti-derived DNA, as the standard karyotype is shared by Mopti and Savanna [4] and the original PE strain did have the 2Rbc inversion rather than 2Rb that is typical of Savanna. Clones from two different PEST strain BAC (Bacterial Artificial Chromosome) libraries had already been end sequenced and physically mapped. When tested, this colony was fully susceptible to P. falciparum from western Kenya [5]
(Text adapted from Collins & Holt 2004)
[edit] Genome
The Anopheles gambiae PEST genome is approximately 270 Mb in length with a GC content of 40.9%. Anopheles has 4 chromosomes, 2 autosomes (designated 2 and 3) and 2 sex chromosomes (designated X and Y). Data related to the genome project have been deposited in GenBank under the project accession: AAAB01000000.
A genome analysis paper was published in 2002[1].
[edit] References
- ↑ 1.0 1.1 Holt, RA, et al. (2002) The genome sequence of the malaria mosquito Anopheles gambiae. Science 5591:129-49 PMID: 12364791
- ↑ 2.0 2.1 Mukabayire and Besansky. (1996) Distribution of T1, Q, Pegasus and mariner transposable elements on the polytene chromosomes of PEST, a standard strain of Anopheles gambiae. Chromosoma Jun;104(8):585-95 PMID: 8662251
- ↑ Mason. (1967) Genetic studies on mutations in species A and B of the Anopheles gambiae complex. Genet Res. Dec;10(3):205-17. PMID: 5587938
- ↑ Toure et al. (1998) The distribution and inversion polymorphism of chromosomally recognized taxa of the A. gambiae complex in Mali, West Africa. Parassitologia. 40(4):477-511. PMID: 10645562
- ↑ Githeko et al. (1992) The reservoir of Plasmodium falciparum malaria in a holoendemic area of western Kenya. Trans R Soc Trop Med Hyg. 86(4):355-8. PMID: 1359683
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