TY - JOUR T1 - Cryptic genetic differentiation of the sex-determining chromosome in the mosquito <em>Aedes aegypti</em> JF - bioRxiv DO - 10.1101/060061 SP - 060061 AU - Albin Fontaine AU - Igor Filipovć AU - Thanyalak Fansiri AU - Ary A. Hoffmann AU - Gordana Rašić AU - Louis Lambrechts Y1 - 2016/01/01 UR - http://biorxiv.org/content/early/2016/06/21/060061.abstract N2 - The evolution of genetic sex determination in eukaryotes is often accompanied by the morphological and genetic differentiation (heteromorphy) of sex chromosomes. Sex determination systems are of particular interest in insect vectors of human pathogens like mosquitoes, for which novel control strategies aim to convert pathogen-transmitting females into non-biting males, or rely on accurate sexing for the release of sterile males. In the major arbovirus vector, the mosquito Aedes aegypti, sex determination is thought to be governed by a dominant male-determining locus (M-locus) spanning only a small portion of an otherwise homomorphic chromosome 1. Here, we provide evidence that the Ae. aegypti sex-determining chromosome is differentiated between males and females over a region considerably larger than the M-locus, showing the features of an XY chromosomal system despite the apparent homomorphy. In laboratory F2 intercrosses, we could not detect recombination events in F1 males along at least 28% of the physical length of chromosome 1, corresponding to 62% of its cytogenetic length. Sex-specific distortions from the expected genotype ratios in the F2 progeny were consistent with the XY system and were not found on distal parts of chromosome 1 or on the other two chromosomes. The same chromosomal region showed substantial genetic differentiation between males and females in unrelated wild populations from Australia and Brazil, pointing to the commonality of these chromosomal features in Ae. aegypti. Our discovery of cryptic sex-chromosome differentiation in Ae. aegypti has important implications for linkage mapping studies, for analyses of population structure, and for the crossing practices to randomize the genetic background of populations in mosquito control strategies. ER -