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J Reprod Dev October 23, 2019; 65 (5): 407-412.
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Expression and function of exportin 6 in full-grown and growing porcine oocytes.

Onuma A , Fujioka YA , Fujii W , Sugiura K , Naito K .

Exportin 6, which functions specifically in the nuclear export of actin family proteins, has been reported to be absent in immature Xenopus oocytes, which have a huge nucleus containing a large amount of actin. In mammalian oocytes, however, the presence and the function of exportin 6 remain uninvestigated. In this study, we assessed the expression and effects of exportin 6 on meiotic resumption in porcine oocytes after cloning porcine exportin 6 cDNA and carrying out overexpression and expression inhibition by mRNA and antisense RNA injection, respectively. We found for the first time that exportin 6 was expressed in mammalian full-grown germinal-vesicle-stage oocytes and was involved in the nuclear export of actin. In contrast, exportin 6 was absent from the growing oocytes, which are meiotically incompetent and maintain the germinal-vesicle structure in the long term; the regulatory mechanism appeared to be active degradation. We examined the effects of exportin 6 on meiotic resumption of porcine oocytes and noted that its expression did not affect the onset time but increased the rate of germinal vesicle breakdown at 24 h via regulation of the nuclear actin level, which directly influences the physical strength of the germinal-vesicle membrane. Our results suggest that exportin 6 affects the nuclear transport of actin and meiotic resumption in mammalian oocytes.

PubMed ID: 31204365
PMC ID: PMC6815735
Article link: J Reprod Dev

Species referenced: Xenopus
Genes referenced: actb rpl19 xpo1 xpo6

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References [+] :
Baarlink, A transient pool of nuclear F-actin at mitotic exit controls chromatin organization. 2017, Pubmed