Dictyostelium discoideum chemotaxis: threshold for directed motion

Area of Science:

• Cellular biology
• Biochemistry
• Biophysics

Background:

• Dictyostelium discoideum is a model organism for studying cell motility and chemotaxis.
• Chemotaxis, the directed movement of cells in response to chemical stimuli, is crucial for various biological processes.
• Cyclic adenosine 3',5'-monophosphate (cAMP) is a key chemoattractant for Dictyostelium discoideum.

Purpose of the Study:

• To investigate the chemotactic response of Dictyostelium discoideum cells to varying gradients of cAMP.
• To determine the relationship between gradient steepness and cell motility and directionality.
• To explore the molecular mechanisms underlying chemotaxis in Dictyostelium discoideum.

Main Methods:

• Utilized microfluidic devices to create controlled, stationary, linear gradients of cAMP.
• Observed and quantified cell behavior, including motility and directionality, using microscopy.
• Analyzed cell responses across a range of cAMP gradient steepnesses.

Main Results:

• Cells showed no directional response in shallow cAMP gradients (< 10(-3) nM/microm).
• Chemotactic speed and motility increased with gradient steepness, plateauing around 10(-1) nM/microm.
• At very steep gradients (> 10 nM/microm), cells lost directionality and motility decreased.

Conclusions:

• Dictyostelium discoideum chemotaxis is sensitive to the steepness of the cAMP gradient.
• An optimal range of gradient steepness exists for maximal chemotactic response.
• The study provides insights into the quantitative aspects of chemotaxis and receptor occupancy.