title: Temporal sampling, resetting, and adaptation orchestrate gradient sensing in sperm.
abstract: Sperm, navigating in a chemical gradient, are exposed to a periodic stream of chemoattractant molecules. The periodic stimulation entrains Ca(2+) oscillations that control looping steering responses. It is not known how sperm sample chemoattractant molecules during periodic stimulation and adjust their sensitivity. We report that sea urchin sperm sampled molecules for 0.2-0.6 s before a Ca(2+) response was produced. Additional molecules delivered during a Ca(2+) response reset the cell by causing a pronounced Ca(2+) drop that terminated the response; this reset was followed by a new Ca(2+) rise. After stimulation, sperm adapted their sensitivity following the Weber-Fechner law. Taking into account the single-molecule sensitivity, we estimate that sperm can register a minimal gradient of 0.8 fM/µm and be attracted from as far away as 4.7 mm. Many microorganisms sense stimulus gradients along periodic paths to translate a spatial distribution of the stimulus into a temporal pattern of the cell response. Orchestration of temporal sampling, resetting, and adaptation might control gradient sensing in such organisms as well.
authors.affiliation: Department of Molecular Sensory Systems, Center of Advanced European Studies and Research, 53175 Bonn, Germany.
authors.forename: Nachiket D
authors.initials: ND
authors.lastname: Kashikar
authors.forename: Luis
authors.initials: L
authors.lastname: Alvarez
authors.forename: Reinhard
authors.initials: R
authors.lastname: Seifert
authors.forename: Ingo
authors.initials: I
authors.lastname: Gregor
authors.forename: Oliver
authors.initials: O
authors.lastname: Jäckle
authors.forename: Michael
authors.initials: M
authors.lastname: Beyermann
authors.forename: Eberhard
authors.initials: E
authors.lastname: Krause
authors.forename: U Benjamin
authors.initials: UB
authors.lastname: Kaupp
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002630:Chemotactic Factors / Q000378:metabolism; D004056:Differential Threshold / Q000502:physiology; D008297:Male; D012617:Sea Urchins / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D013081:Sperm Motility / Q000502:physiology; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology*
chemical_list: D002630:Chemotactic Factors; D002118:Calcium