title: Drosophila sperm swim backwards in the female reproductive tract and are activated via TRPP2 ion channels.
abstract: BACKGROUND
  Sperm have but one purpose, to fertilize an egg. In various species including Drosophila melanogaster female sperm storage is a necessary step in the reproductive process. Amo is a homolog of the human transient receptor potential channel TRPP2 (also known as PKD2), which is mutated in autosomal dominant polycystic kidney disease. In flies Amo is required for sperm storage. Drosophila males with Amo mutations produce motile sperm that are transferred to the uterus but they do not reach the female storage organs. Therefore Amo appears to be a mediator of directed sperm motility in the female reproductive tract but the underlying mechanism is unknown.
  
  
  RESULTS
  Amo exhibits a unique expression pattern during spermatogenesis. In spermatocytes, Amo is restricted to the endoplasmic reticulum (ER) whereas in mature sperm, Amo clusters at the distal tip of the sperm tail. Here we show that flagellar localization of Amo is required for sperm storage. This raised the question of how Amo at the rear end of sperm regulates forward movement into the storage organs. In order to address this question, we used in vivo imaging of dual labelled sperm to demonstrate that Drosophila sperm navigate backwards in the female reproductive tract. In addition, we show that sperm exhibit hyperactivation upon transfer to the uterus. Amo mutant sperm remain capable of reverse motility but fail to display hyperactivation and directed movement, suggesting that these functions are required for sperm storage in flies.
  
  
  CONCLUSIONS
  Amo is part of a signalling complex at the leading edge of the sperm tail that modulates flagellar beating and that guides a backwards path into the storage organs. Our data support an evolutionarily conserved role for TRPP2 channels in cilia.
authors.affiliation: Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America. michael.koettgen@uniklinik-freiburg.de
authors.forename: Michael
authors.initials: M
authors.lastname: Köttgen
authors.forename: Alexis
authors.initials: A
authors.lastname: Hofherr
authors.forename: Weizhe
authors.initials: W
authors.lastname: Li
authors.forename: Kristy
authors.initials: K
authors.lastname: Chu
authors.forename: Stacey
authors.initials: S
authors.lastname: Cook
authors.forename: Craig
authors.initials: C
authors.lastname: Montell
authors.forename: Terry
authors.initials: T
authors.lastname: Watnick
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D029721:Drosophila Proteins / Q000737:chemistry / Q000502:physiology; D004331:Drosophila melanogaster; D005260:Female; D005455:Fluorescent Antibody Technique; D005836:Genitalia, Female; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology*; D050396:TRPP Cation Channels / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D008565:Membrane Proteins; D050396:TRPP Cation Channels; C482645:almost there protein, Drosophila