title: Molecular analysis of a para sodium channel gene from pyrethroid-resistant head lice, Pediculus humanus capitis (Anoplura: Pediculidae).
abstract: The problem of pyrethroid-resistance in head lice, Pediculus humanus capitis (De Geer), is growing worldwide, and an insensitive sodium channel is suspected as the major mechanism of this resistance. We sequenced an open reading frame (ORF) encoding for the para-orthologous sodium channel from an insecticide-susceptible strain of the body louse, Pediculus humanus humanus (L.), based on conserved peptide sequences and a known partial gene sequence. Phenothrin-susceptible and -resistant head louse colonies from Japanese were individually analyzed for point mutations of the sodium channel cDNA; susceptible head and body lice differed in double homozygous synonymous substitutions. The resistant head lice shared 23 base substitutions homozygously, in which four resulted in amino acid substitutions: D11E in the N-terminal inner-membrane segment; M850T in the outer-membrane loop between segments four and five of domain II; T952I and L955 F in the trans-membrane segment five of domain II. The latter two substitutions coincided with those of pyrethroid-resistant head lice in the U.S. and U.K. (Lee et al. 2000), within the available published information on the peptide sequences. The potential mechanisms of head louse pyrethroid-resistance are discussed based on the four structural changes of the target molecule.
authors.affiliation: Department of Medical Entomology, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo 162-8640, Japan. tomita@nih.go.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Tomita
authors.forename: Noboru
authors.initials: N
authors.lastname: Yaguchi
authors.forename: Minoru
authors.initials: M
authors.lastname: Mihara
authors.forename: Masakazu
authors.initials: M
authors.lastname: Takahashi
authors.forename: Noriaki
authors.initials: N
authors.lastname: Agui
authors.forename: Shinji
authors.initials: S
authors.lastname: Kasai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004351:Drug Resistance / Q000235:genetics*; D006801:Humans; D007306:Insecticides / Q000633:toxicity*; D008969:Molecular Sequence Data; D010374:Pediculus / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D011722:Pyrethrins / Q000633:toxicity*; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry / Q000235:genetics*
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D012333:RNA, Messenger; D015222:Sodium Channels