Drosophila sperm swim backwards in the female reproductive tract and are activated via TRPP2 ion channels |
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Authors: | Köttgen Michael Hofherr Alexis Li Weizhe Chu Kristy Cook Stacey Montell Craig Watnick Terry |
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Institution: | Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America. michael.koettgen@uniklinik-freiburg.de |
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Abstract: | BackgroundSperm 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.Methodology/Principal FindingsAmo 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/SignificanceAmo 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. |
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