MDia1/3 generate cortical F-actin meshwork in Sertoli cells that is continuous with contractile F-actin bundles and indispensable for spermatogenesis and male fertility.

Satoko Sakamoto,Takayoshi Fuu,Yoshitaka Fujihara,Pakorn Kanchanawong,Shosei Yoshida,Shuh Narumiya,Dean Thumkeo,Zhen Zhang,Naoki Watanabe,Hiroshi Ohta,Shuangru Huang,Mitinori Saitou,Masahito Ikawa,Kentaro Shimada,Sadanori Watanabe,Mariana Wolfner

doi:10.1371/journal.pbio.2004874

Abstract

Formin is one of the two major classes of actin binding proteins (ABPs) with nucleation and polymerization activity. However, despite advances in our understanding of its biochemical activity, whether and how formins generate specific architecture of the actin cytoskeleton and function in a physiological context in vivo remain largely obscure. It is also unknown how actin filaments generated by formins interact with other ABPs in the cell. Here, we combine genetic manipulation of formins mammalian diaphanous homolog1 (mDia1) and 3 (mDia3) with superresolution microscopy and single-molecule imaging, and show that the formins mDia1 and mDia3 are dominantly expressed in Sertoli cells of mouse seminiferous tubule and together generate a highly dynamic cortical filamentous actin (F-actin) meshwork that is continuous with the contractile actomyosin bundles. Loss of mDia1/3 impaired these F-actin architectures, induced ectopic noncontractile espin1-containing F-actin bundles, and disrupted Sertoli cell–germ cell interaction, resulting in impaired spermatogenesis. These results together demonstrate the previously unsuspected mDia-dependent regulatory mechanism of cortical F-actin that is indispensable for mammalian sperm development and male fertility.

Highlights

Filamentous actin (F-actin) nucleation and polymerization are controlled by actin nucleators, including actin-related protein2/3 (Arp2/3) and formin, in mammalian cells
We showed that the interaction between developing sperm and Sertoli cells is critical for sperm morphogenesis
We further unraveled that this interaction is strongly dependent on the cortical F-actin meshwork and contractile actomyosin bundles of Sertoli cells, and that two actin polymerization and nucleation factors of the formin family, mammalian diaphanous homolog1 (mDia1) and mDia3, are involved in the generation of both actin-based structures

Summary

Introduction

Filamentous actin (F-actin) nucleation and polymerization are controlled by actin nucleators, including actin-related protein2/3 (Arp2/3) and formin, in mammalian cells. To unravel mDia-dependent Factin structures in the mammalian body and explore their physiological functions in vivo, we generated mice deficient in each isoform and analyzed their phenotypes [3,4,5]. These studies showed the functional redundancy between mDia and mDia isoforms and demonstrated that mDia1/3-mediated F-actin is critical for neuroblast migration [5] and neuroepithelium integrity [6] in the developing brain, and mediates presynaptic plasticity of mature neurons in the adult brain [7]. The contribution and function of mDia-mediated F-actin in other systems remain an open question

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Discussion

Conclusion