title: Remarkable diversity of intron-1 of the para voltage-gated sodium channel gene in an Anopheles gambiae/Anopheles coluzzii hybrid zone.
abstract: BACKGROUND
  Genomic differentiation between Anopheles gambiae and Anopheles coluzzii--the major malaria vectors in sub-Saharan Africa--is localized into large "islands" toward the centromeres of chromosome-X and the two autosomes. Linkage disequilibrium between these genomic islands was first detected between species-specific polymorphisms within ribosomal DNA genes (IGS-rDNA) on the X-chromosome and a single variant at position 702 of intron 1 (Int-1702) of the para Voltage-Gated Sodium Channel (VGSC) gene on chromosome arm 2 L. Intron-1 sequence data from West and Central Africa revealed two clearly distinct and species-specific haplogroups, each characterized by very low polymorphism, which has been attributed to a selective sweep. The aim of this study was to analyse Int-1 sequence diversity in A. gambiae and A. coluzzii populations from the Far-West of their range, in order to assess whether this selective-sweep signature could persist in a zone of high interspecific hybridization.
  
  
  METHODS
  A 531 bp region of VGSC Int-1 was sequenced in 21 A. coluzzii, 31 A. gambiae, and 12 hybrids from The Gambia and Guinea Bissau, located within the Far-West geographical region, and in 53 A. gambiae s.l. samples from the rest of the range.
  
  
  RESULTS
  Far-West samples exhibit dramatic Int-1 polymorphism, far higher within each country than observed throughout the rest of the species range. Moreover, patterning of haplotypes within A. coluzzii confirms previous evidence of a macro-geographic subdivision into a West and a Central African genetic cluster, and reveals a possible genetic distinction of A. coluzzii populations from the Far-West.
  
  
  CONCLUSIONS
  The results suggest a relaxation of selective pressures acting across the VGSC gene region in the hybrid zone. Genetic differentiation in the Far-West could be attributable to a founder effect within A. coluzzii, with subsequent extensive gene flow with secondarily-colonizing A. gambiae, potentially yielding a novel insight on the dynamic processes impacting genetic divergence of these key malaria vectors.
authors.forename: Federica
authors.initials: F
authors.lastname: Santolamazza
authors.forename: Beniamino
authors.initials: B
authors.lastname: Caputo
authors.forename: Davis C
authors.initials: DC
authors.lastname: Nwakanma
authors.forename: Caterina
authors.initials: C
authors.lastname: Fanello
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Petrarca
authors.forename: David J
authors.initials: DJ
authors.lastname: Conway
authors.forename: David
authors.initials: D
authors.lastname: Weetman
authors.forename: Joao
authors.initials: J
authors.lastname: Pinto
authors.affiliation: Dipartimento di Sanità Pubblica e Malattie Infettive, Istituto Pasteur-Fondazione Cenci-Bolognetti, Università "Sapienza", Piazzale Aldo Moro 5, Rome, 00185, Italy. emiliano.mancini@uniroma1.it.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Mancini
authors.forename: Alessandra
authors.initials: A
authors.lastname: della Torre
mesh_terms: D000818:Animals; D000852:Anopheles / Q000235:genetics*; D005714:Gambia; D051456:Gene Flow; D014644:Genetic Variation; D006169:Guinea-Bissau; D007438:Introns; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D061566:Voltage-Gated Sodium Channels / Q000235:genetics*
chemical_list: D061566:Voltage-Gated Sodium Channels