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Reorganization of actin filaments by ADF/cofilin is involved in formation of microtubule structures during Xenopus oocyte maturation.

Yamagishi Y, Abe H - Mol. Biol. Cell (2015)

Bottom Line: Suppression of XAC dephosphorylation by anti-XSSH antibody injection inhibited both actin filament reorganization and proper formation and localization of both the MTOC-TMA and meiotic spindles.Nocodazole also caused the MTOC-TMA and the cytoplasmic actin filaments at its base region to disappear, which further impeded disassembly of intranuclear actin filaments from the vegetal side.XAC appears to reorganize cytoplasmic actin filaments required for precise assembly of the MTOC and, together with the MTOC-TMA, regulate the intranuclear actin filament disassembly essential for meiotic spindle formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Nanobiology, Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan.

No MeSH data available.


Related in: MedlinePlus

Effects of injection of 2.5 mg/ml chick S3A-cofilin (A, B) and treatment of 20 μg/ml nocodazole (C, D) on disassembly of intranuclear actin filaments and assembly of the MTOC-TMA. Midsagittal sections of S3A-cofilin–injected oocytes immediately before (A) or immediately after (B) GVBD were double stained with TMR-phalloidin (F-actin) and anti-tubulin antibody (MT). (A) Assembly of the cytoplasmic actin filaments and microtubule bundles (arrows) at the basal region of the nuclei is clearly visible in S3A-cofilin–injected oocytes. Twelve oocytes from six different females were examined. (B) Assembly of the MTOC-TMA is affected by S3A-cofilin injection. The TMA itself is well developed, but actin staining disappears from the base of the split region of the MTOC-TMA (arrowhead). Atypical microtubule structures have formed at the animal side as they surround the nuclear region (arrows). A faint staining of actin filaments (indicated by arrow in the F-actin panel) is also visible around the animal side of the residual nuclear actin filaments. Six oocytes from three different females were examined. Midsagittal sections of 20 μg/ml nocodazole–treated oocytes immediately after GVBD were double stained with anti-lamin and anti-tubulin antibodies (C) or TMR-phalloidin and anti-tubulin antibody (D). Merged and DIC images are also shown. Arrows indicate bleb-like protrusions characteristic of nocodazole-treated oocyte nuclei. Disassembly of the intranuclear actin filaments from the vegetal side is retarded. Twelve oocytes from three different females were examined.
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Figure 7: Effects of injection of 2.5 mg/ml chick S3A-cofilin (A, B) and treatment of 20 μg/ml nocodazole (C, D) on disassembly of intranuclear actin filaments and assembly of the MTOC-TMA. Midsagittal sections of S3A-cofilin–injected oocytes immediately before (A) or immediately after (B) GVBD were double stained with TMR-phalloidin (F-actin) and anti-tubulin antibody (MT). (A) Assembly of the cytoplasmic actin filaments and microtubule bundles (arrows) at the basal region of the nuclei is clearly visible in S3A-cofilin–injected oocytes. Twelve oocytes from six different females were examined. (B) Assembly of the MTOC-TMA is affected by S3A-cofilin injection. The TMA itself is well developed, but actin staining disappears from the base of the split region of the MTOC-TMA (arrowhead). Atypical microtubule structures have formed at the animal side as they surround the nuclear region (arrows). A faint staining of actin filaments (indicated by arrow in the F-actin panel) is also visible around the animal side of the residual nuclear actin filaments. Six oocytes from three different females were examined. Midsagittal sections of 20 μg/ml nocodazole–treated oocytes immediately after GVBD were double stained with anti-lamin and anti-tubulin antibodies (C) or TMR-phalloidin and anti-tubulin antibody (D). Merged and DIC images are also shown. Arrows indicate bleb-like protrusions characteristic of nocodazole-treated oocyte nuclei. Disassembly of the intranuclear actin filaments from the vegetal side is retarded. Twelve oocytes from three different females were examined.

Mentions: Next, to counteract the antibody injection, we injected constitutively active chick S3A cofilin into oocytes in order to increase actin dynamics (thereby preventing proper regulation). Using MAB-22, we could easily confirm introduction of chick cofilin into oocytes by either immunoblotting or immunofluorescence microscopy. Immediately before GVBD, the localization of actin filaments and micro­tubules in injected oocytes seemed to be the same as in normal oocytes (Figure 7A; compare with Figures 3B and 5A, control). However, an atypically curved and split MTOC-TMA was formed immediately after GVBD (Figure 7B). Although the TMA was well developed, actin staining appeared to be less evident, especially at the base of the split MTOC-TMA (Figure 7B, arrowhead). In addition, microtubules formed unusual structures at the animal side as they surround the nuclear region; faint staining of actin filaments was also visible in this region. These observations were consistently reproduced, and three additional examples are shown in Supplemental Figure S7B. Each TMA of the S3A cofilin-injected oocytes developed and elongated much more than that of control oocytes. The residual intranuclear actin filaments disappeared more rapidly than those of control oocytes. These results suggest that overactivity of ADF/cofilin disassembles the actin filaments at the base of the MTOC-TMA to inhibit its precise formation.


Reorganization of actin filaments by ADF/cofilin is involved in formation of microtubule structures during Xenopus oocyte maturation.

Yamagishi Y, Abe H - Mol. Biol. Cell (2015)

Effects of injection of 2.5 mg/ml chick S3A-cofilin (A, B) and treatment of 20 μg/ml nocodazole (C, D) on disassembly of intranuclear actin filaments and assembly of the MTOC-TMA. Midsagittal sections of S3A-cofilin–injected oocytes immediately before (A) or immediately after (B) GVBD were double stained with TMR-phalloidin (F-actin) and anti-tubulin antibody (MT). (A) Assembly of the cytoplasmic actin filaments and microtubule bundles (arrows) at the basal region of the nuclei is clearly visible in S3A-cofilin–injected oocytes. Twelve oocytes from six different females were examined. (B) Assembly of the MTOC-TMA is affected by S3A-cofilin injection. The TMA itself is well developed, but actin staining disappears from the base of the split region of the MTOC-TMA (arrowhead). Atypical microtubule structures have formed at the animal side as they surround the nuclear region (arrows). A faint staining of actin filaments (indicated by arrow in the F-actin panel) is also visible around the animal side of the residual nuclear actin filaments. Six oocytes from three different females were examined. Midsagittal sections of 20 μg/ml nocodazole–treated oocytes immediately after GVBD were double stained with anti-lamin and anti-tubulin antibodies (C) or TMR-phalloidin and anti-tubulin antibody (D). Merged and DIC images are also shown. Arrows indicate bleb-like protrusions characteristic of nocodazole-treated oocyte nuclei. Disassembly of the intranuclear actin filaments from the vegetal side is retarded. Twelve oocytes from three different females were examined.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Figure 7: Effects of injection of 2.5 mg/ml chick S3A-cofilin (A, B) and treatment of 20 μg/ml nocodazole (C, D) on disassembly of intranuclear actin filaments and assembly of the MTOC-TMA. Midsagittal sections of S3A-cofilin–injected oocytes immediately before (A) or immediately after (B) GVBD were double stained with TMR-phalloidin (F-actin) and anti-tubulin antibody (MT). (A) Assembly of the cytoplasmic actin filaments and microtubule bundles (arrows) at the basal region of the nuclei is clearly visible in S3A-cofilin–injected oocytes. Twelve oocytes from six different females were examined. (B) Assembly of the MTOC-TMA is affected by S3A-cofilin injection. The TMA itself is well developed, but actin staining disappears from the base of the split region of the MTOC-TMA (arrowhead). Atypical microtubule structures have formed at the animal side as they surround the nuclear region (arrows). A faint staining of actin filaments (indicated by arrow in the F-actin panel) is also visible around the animal side of the residual nuclear actin filaments. Six oocytes from three different females were examined. Midsagittal sections of 20 μg/ml nocodazole–treated oocytes immediately after GVBD were double stained with anti-lamin and anti-tubulin antibodies (C) or TMR-phalloidin and anti-tubulin antibody (D). Merged and DIC images are also shown. Arrows indicate bleb-like protrusions characteristic of nocodazole-treated oocyte nuclei. Disassembly of the intranuclear actin filaments from the vegetal side is retarded. Twelve oocytes from three different females were examined.
Mentions: Next, to counteract the antibody injection, we injected constitutively active chick S3A cofilin into oocytes in order to increase actin dynamics (thereby preventing proper regulation). Using MAB-22, we could easily confirm introduction of chick cofilin into oocytes by either immunoblotting or immunofluorescence microscopy. Immediately before GVBD, the localization of actin filaments and micro­tubules in injected oocytes seemed to be the same as in normal oocytes (Figure 7A; compare with Figures 3B and 5A, control). However, an atypically curved and split MTOC-TMA was formed immediately after GVBD (Figure 7B). Although the TMA was well developed, actin staining appeared to be less evident, especially at the base of the split MTOC-TMA (Figure 7B, arrowhead). In addition, microtubules formed unusual structures at the animal side as they surround the nuclear region; faint staining of actin filaments was also visible in this region. These observations were consistently reproduced, and three additional examples are shown in Supplemental Figure S7B. Each TMA of the S3A cofilin-injected oocytes developed and elongated much more than that of control oocytes. The residual intranuclear actin filaments disappeared more rapidly than those of control oocytes. These results suggest that overactivity of ADF/cofilin disassembles the actin filaments at the base of the MTOC-TMA to inhibit its precise formation.

Bottom Line: Suppression of XAC dephosphorylation by anti-XSSH antibody injection inhibited both actin filament reorganization and proper formation and localization of both the MTOC-TMA and meiotic spindles.Nocodazole also caused the MTOC-TMA and the cytoplasmic actin filaments at its base region to disappear, which further impeded disassembly of intranuclear actin filaments from the vegetal side.XAC appears to reorganize cytoplasmic actin filaments required for precise assembly of the MTOC and, together with the MTOC-TMA, regulate the intranuclear actin filament disassembly essential for meiotic spindle formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Nanobiology, Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan.

No MeSH data available.


Related in: MedlinePlus