DNA Double-Strand Breaks Induce the Nuclear Actin Filaments Formation in Cumulus-Enclosed Oocytes but Not in Denuded Oocytes

Abstract

As a gamete, oocyte needs to maintain its genomic integrity and passes this haploid genome to the next generation. However, fully-grown mouse oocyte cannot respond to DNA double-strand breaks (DSBs) effectively and it is also unable to repair them before the meiosis resumption. To compensate for this disadvantage and control the DNA repair events, oocyte needs the cooperation with its surrounding cumulus cells. Recently, evidences have shown that nuclear actin filament formation plays roles in cellular DNA DSB repair. To explore whether these nuclear actin filaments are formed in the DNA-damaged oocytes, here, we labeled the filament actins in denuded oocytes (DOs) and cumulus-enclosed oocytes (CEOs). We observed that the nuclear actin filaments were formed only in the DNA-damaged CEOs, but not in DOs. Formation of actin filaments in the nucleus was an event downstream to the DNA damage response. Our data also showed that the removal of cumulus cells led to a reduction in the nuclear actin filaments in oocytes. Knocking down of the Adcy1 gene in cumulus cells did not affect the formation of nuclear actin filaments in oocytes. Notably, we also observed that the nuclear actin filaments in CEOs could be induced by inhibition of gap junctions. From our results, it was confirmed that DNA DSBs induce the nuclear actin filament formation in oocyte and which is controlled by the cumulus cells.

Nuclear F-actin and myosins drive relocalization of heterochromatic breaks

“…Nuclear actin filaments (F-actin) form in response to DSBs in mammalian cells, and have poorly understood functions in repair 13–15 . We tested the role of actin polymerization in relocalization of heterochromatic DSBs.…”

The Nature of Actin-Family Proteins in Chromatin-Modifying Complexes

“…Interestingly, recent research has revealed that nuclear actin plays an important role in DNA repair processes as well, opening a new domain of research in the nuclear actin field ( Andrin et al, 2012 ; Belin et al, 2015 ; Spichal et al, 2016 ; Caridi et al, 2018 ; Schrank et al, 2018 ). Actin filament formation is induced in the nucleus following DNA double-strand breaks and is thought to have crucial roles in promoting their effective repair ( Andrin et al, 2012 ; Sun et al, 2017 ; Caridi et al, 2018 ; Schrank et al, 2018 ). Moreover, many repair factors such as the nuclease Mre11, recombinase Rad51, and non-homologous end-joining heterodimer Ku70-Ku80 associate with polymerized actin in vitro , and are suggested to help recruit or stabilize these repair factors at the damage site ( Andrin et al, 2012 ).…”

DMBA acts on cumulus cells to desynchronize nuclear and cytoplasmic maturation of pig oocytes

“…However, DSBs appeared only in oocytes from COCs treated by DMBA, but not in CDOs. This could be explained by the fact that cumulus cells were previously shown to control the DSB response 33 and the DSB-induced formation of nuclear actin filament in oocytes 34 . Thirdly, apoptosis could be induced by DSBs in oocytes 17 , and we found DMBA could induce higher incidence of early apoptosis, but again, only in the COC system.…”