Chicken primordial germ cell motility in response to stem cell factor sensing

Abstract

Avian primordial germ cells (PGCs) are destined to migrate a long distance from their extra embryonic region via the vascular system to the gonadal ridges where they form the germ cells. Although PGC migration is crucial for a genetic continuation to the next generation, the factors and mechanisms that control their migration remain largely unknown. In the present study the chemotactic effect of stem cell factor (SCF) was examined on chicken blood circulating PGCs (cPGC), employing 3D chemotaxis slides and time-lapsed imaging analyses as an in vitro study model. Upon in vitro exposure to an SCF gradient, 77.1% (54 out of 70) of cPGCs showed a clear response, of which 48.1% (26 out of 54) polarized with the consecutive formation of a persistent membrane protrusion and significant directional migration towards the gradient and the others showed transient membrane protrusions. In contrast, the controls and apparently SCF unresponsive cPGCs and c-kit-negative red blood cells (RBCs) showed only cytoplasmic cycling with random formations of membrane blebbing and no directional migration. Significant (p< 0.05) differences between the SCF-treated and control cPGCs and RBCs were found in the migration parameters of eccentricity, accumulated and Euclidean distances, and migration velocity. The SCF-treated PGCs also revealed a chemotactic response, as judged by their significant displacement of center of mass and Rayleigh test. Complete inhibition of all the SCF-induced responses in PGCs was found following pretreatment of the cPGCs with 10 mM of the c-kit inhibitor, STI57l, prior to SCF exposure. In addition, cPGCs were found to be positive for c-kit expression using a polyclonal goat anti-mouse c-kit primary antibody, suggesting that the cPGCs were capable of SCF sensing and the potential involvement of SCF/c-kit in the chemotactic migration. Therefore, SCF is suggested to function as a chemoattractant in the migration of chicken cPGC.