Live imaging screen reveals that TYRO3 and GAK ensure accurate spindle positioning in human cells.

ABSTRACT

Proper spindle positioning is crucial for spatial cell division control. Spindle positioning in human cells relies on a ternary complex comprising Gαi1-3, LGN and NuMA, which anchors dynein at the cell cortex, thus enabling pulling forces to be exerted on astral microtubules. We develop a live imaging siRNA-based screen using stereotyped fibronectin micropatterns to uncover components modulating spindle positioning in human cells, testing 1280 genes, including all kinases and phosphatases. We thus discover 16 components whose inactivation dramatically perturbs spindle positioning, including tyrosine receptor kinase 3 (TYRO3) and cyclin G associated kinase (GAK). TYRO3 depletion results in excess NuMA and dynein at the cortex during metaphase, similar to the effect of blocking the TYRO3 downstream target phosphatidylinositol 3-kinase (PI3K). Furthermore, depletion of GAK leads to impaired astral microtubules, similar to the effect of downregulating the GAK-interactor Clathrin. Overall, our work uncovers components and mechanisms governing spindle positioning in human cells.