Repository logo

SPIN90 associates with mDia1 and the Arp2/3 complex to regulate cortical actin organization.

Accepted version

Change log


Cao, Luyan 
Yonis, Amina 
Vaghela, Malti 
Barriga, Elias H 
Chugh, Priyamvada 


Cell shape is controlled by the submembranous cortex, an actomyosin network mainly generated by two actin nucleators: the Arp2/3 complex and the formin mDia1. Changes in relative nucleator activity may alter cortical organization, mechanics and cell shape. Here we investigate how nucleation-promoting factors mediate interactions between nucleators. In vitro, the nucleation-promoting factor SPIN90 promotes formation of unbranched filaments by Arp2/3, a process thought to provide the initial filament for generation of dendritic networks. Paradoxically, in cells, SPIN90 appears to favour a formin-dominated cortex. Our in vitro experiments reveal that this feature stems mainly from two mechanisms: efficient recruitment of mDia1 to SPIN90-Arp2/3 nucleated filaments and formation of a ternary SPIN90-Arp2/3-mDia1 complex that greatly enhances filament nucleation. Both mechanisms yield rapidly elongating filaments with mDia1 at their barbed ends and SPIN90-Arp2/3 at their pointed ends. Thus, in networks, SPIN90 lowers branching densities and increases the proportion of long filaments elongated by mDia1.



Actin Cytoskeleton, Actin-Related Protein 2-3 Complex, Actins, Adaptor Proteins, Signal Transducing, Animals, Blastula, Cell Shape, Embryo, Nonmammalian, Formins, Humans, Melanoma, Muscle Proteins, Xenopus laevis

Journal Title

Nat Cell Biol

Conference Name

Journal ISSN


Volume Title



Springer Science and Business Media LLC


All rights reserved
Medical Research Council (MC_UU_00012/5)