Author response: A K+-selective CNG channel orchestrates Ca2+ signalling in zebrafish sperm
Year: 2015
Type: peer-review
Abstract: Mammalian sperm cells fertilize egg cells inside the female’s body; while for fish and other marine animals it is common for fertilization to take place outside in the environment. In general, sperm cells become attracted to egg cells by various chemical or physical signals. Sperm detect these cues and generate electrical signals that control their own movements and eventually guide sperm to the egg. In 2009, researchers identified a potassium ion channel, called CNGK, that starts the electrical signal in the sperm cells of sea urchins. This channel is activated by signalling molecules inside cells, called ‘cyclic nucleotides’, and its activity ultimately leads to calcium ions flowing into the sperm cell’s tail. This influx of calcium ions in turn controls the beating of the tail and, thereby, steers the sperm cell towards the egg. It was previously thought that this CNGK channel is found only in animals without a backbone (i.e. in invertebrates). However, Fechner et al. – including some of the researchers involved in the 2009 work – now report that the CNGK channel also exists in the sperm cells of a freshwater fish, the zebrafish. Unexpectedly, the CNGK channel is located in the heads of this fish’s sperm cells rather than in the tails. Electrophysiological experiments then revealed that the fish version of CNGK is not activated by cyclic nucleotides, but is activated when the inside of the cell becomes more alkaline. In zebrafish sperm, a more alkaline pH inside the cell causes calcium ions to flow in and this influx of calcium ions triggers a unique spinning-like swimming movement that is different from the swimming of other sperm from other species. Fechner et al. suspect that this unusual swimming behaviour guides sperm through a small hole in the protective coating of fish eggs, which eventually leads to fertilization. These findings suggest that while channel proteins found in sperm cells from different species look similar and serve similar roles, they are activated in ways that can be very different.
Source: eLife
Authors: Sylvia Fechner, Luis Alvarez, Wolfgang Bönigk, Astrid Müller, Thomas K Berger, Rene Pascal, Christian Trötschel, Ansgar Poetsch, Gabriel Stölting, Kellee R Siegfried, Elisabeth Kremmer, Reinhard Seifert, U Benjamin Kaupp
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,500
OpenAlex ID: W2988538940