Biol Open.: co-auth.: group Vastenhouw

Biol Open. 2023 Apr 18;bio.059783. doi: 10.1242/bio.059783. Online ahead of print.

Actin filaments accumulated in the nucleus and remain in the vicinity of condensing chromosomes during prophase in zebrafish early embryo

Haruka Oda 1Yuko Sato 1Shigehiro A Kawashima 2Yusuke Fujiwara 2Máté Pálfy 3Edlyn Wu 3 4Nadine L Vastenhouw 3 4Motomu Kanai 2Hiroshi Kimura 1


In the cytoplasm, filamentous actin (F-actin) plays a critical role in cell regulation, including cell migration, stress fiber formation, and cytokinesis. Recent studies have shown that actin filaments that form in the nucleus are associated with diverse functions. Here, using live imaging of an F-actin-specific probe, superfolder GFP-tagged utrophin (UtrCH-sfGFP), we demonstrated the dynamics of nuclear actin in zebrafish (Danio rerio) embryos. In early zebrafish embryos up to around the high stage, UtrCH-sfGFP increasingly accumulated in nuclei during the interphase and reached a peak during the prophase. After nuclear envelope breakdown (NEBD), patches of UtrCH-sfGFP remained in the vicinity of condensing chromosomes during the prometaphase to metaphase. When zygotic transcription was inhibited by injecting α-amanitin, the nuclear accumulation of UtrCH-sfGFP was still observed at the sphere and dome stages, suggesting that zygotic transcription may induce a decrease in nuclear F-actin. The accumulation of F-actin in nuclei may contribute to proper mitotic progression of large cells with rapid cell cycles in zebrafish early embryos, by assisting in NEBD, chromosome congression, and/or spindle assembly.

Keywords: Live-cell imaging; Nuclear actin; Zebrafish embryo.