CELL CYCLE 2016, VOL. 15, NO. 16, 2101 http://dx.doi.org/10.1080/15384101.2016.1205411
CELL CYCLE NEWS & VIEWS
A novel role of Beclin-1, cytokinetic abscission Hak-Jae Chunga and Inchul Choib a National Institute of Animal Science, Rural Development Administration, Jeollabuk-do, Republic of Korea; bDivision of Animal and Dairy Sciences, College of Agriculture and Life Sciences, Chungnam National University, Daejeon, Republic of Korea
ARTICLE HISTORY Received 12 June 2016; Accepted 18 June 2016 KEYWORDS abscission; beclin-1; cytokinesis; meiosis; oocyte
The success of oocyte meiosis is contingent upon symmetric nuclear division and asymmetric cytokinesis that plays an important role in the retention of maternal components necessary for cellular reprogramming and early embryo development. The failure nullifies all of the previous meiotic events including chromosome alignments and segregation. Beclin1, a mammalian ortholog of the Atg6/vaculolar protein sorting (Vps)-30 protein in yeast, has been reported to induce autophagy and apoptosis via phosphatidylinositol 3-kinase class III (PI3K-III).1 In particular, Beclin 1 was markedly increased in in vitro cultured foetal oocytes, suggesting autophagic and necrotic feature during meiotic progression.2 However, in this volume of Cell cycle, Jeong Su Oh and his colleagues provide a new insight into a novel role of Beclin-1 and its regulation during oocyte meiosis.3 Ablation of Beclin-1 led to cytokinetic abscission failure as a part of PI3K-III lipid-kinase complex but autophagy defect during meiotic maturation.3 This report raises questions about autophagy function of Beclin-1 and oocyte/embryo competency during maturation and pre-implantation development. Recently, it was reported that induction of autophagy treated with rapamycin (mTOR inhibitor) improved the nuclear and cytoplasmic maturation, and preimplantation development in porcine oocytes and embryos.4,5 Moreover, Beclin 1 and microtubule-associate protein 1-light chain 3 (LC3) were up-regulated in morphologically poor oocytes treated with rapamycin. Thus, it does not appear that previous studies support the results of Beclin-1 knock down experiments, abscission failure and nonautophogy defect in meiotic oocytes. However, the improvement may be attributed to an increase in Beclin-1 expression because developmental competency of oocytes treated with rapamycin during 22–42 hours of in vitro maturation (IVM) is comparable to those during 0–42 hours of IVM in porcine oocytes that took 30–48 hours for first polar body extrusion,6 implying that upregulated Beclin-1 in MI and MII staged porcine oocyte might lead to proper cytokinesis.
Understanding the regulation of PI3K-III complex including Beclin-1 is difficult in terms of cytokinesis and autophagy pathway. In the current Beclin-1 knock down study, the authors clarified that Beclin-1 is essential for the abscission via recruitment of ZFYVE26, a PI(3)P-binding protein, to the midbody, but not directly is involved in autophagy during meiotic cytokinesis using autophagy inhibitors such as 3-methyladenine and bafilomycin A1.
Disclosure of potential conflicts of interest No potential conflicts of interest were disclosed.
References [1] Kang R, et al. The Beclin 1 network regulates autophagy and apoptosis. Cell Death Differ 2011; 18(4):571–80; PMID:21311563; http://dx. doi.org/10.1038/cdd.2010.191 [2] De Felici M, et al. Cell death in fetal oocytes: many players for multiple pathways. Autophagy 2008; 4(2):240-2; PMID:18094606; http://dx. doi.org/10.4161/auto.5410 [3] You SY, et al. Beclin-1 knockdown shows abscission failure but not autophagy defect during oocyte meiotic maturation. Cell Cycle 2016; 15(12):1611–9; PMID:27149384; http://dx.doi.org/10.1080/15384101. 2016.1181235 [4] Song BS, et al. Induction of autophagy during in vitro maturation improves the nuclear and cytoplasmic maturation of porcine oocytes. Reprod Fertil Dev 2014; 26(7):974-81; PMID:23902659; http://dx.doi. org/10.1071/RD13106 [5] Lee J, et al. Rapamycin treatment during in vitro maturation of oocytes improves embryonic development after parthenogenesis and somatic cell nuclear transfer in pigs. J Vet Sci 2015; 16(3):373-80; PMID: 25797293; http://dx.doi.org/10.4142/jvs.2015.16.3.373 [6] Wang ZW, et al. Cytoplasmic Determination of Meiotic Spindle Size Revealed by a Unique Inter-Species Germinal Vesicle Transfer Model. Sci Rep 2016; 6:19827; PMID:26813698; http://dx.doi.org/10.1038/ srep19827
CONTACT Inchul Choi [email protected] Division of Animal and Dairy Sciences, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea. News and Views to: You SY, et al. Beclin-1 knockdown shows abscission failure but not autophagy defect during oocyte meiotic maturation. Cell Cycle 2016; 15(12):1611-9; PMID:27149384; http://dx.doi.org/10.1080/15384101.2016.1181235 © 2016 Taylor & Francis
CELL CYCLE NEWS & VIEWS
A novel role of Beclin-1, cytokinetic abscission Hak-Jae Chunga and Inchul Choib a National Institute of Animal Science, Rural Development Administration, Jeollabuk-do, Republic of Korea; bDivision of Animal and Dairy Sciences, College of Agriculture and Life Sciences, Chungnam National University, Daejeon, Republic of Korea
ARTICLE HISTORY Received 12 June 2016; Accepted 18 June 2016 KEYWORDS abscission; beclin-1; cytokinesis; meiosis; oocyte
The success of oocyte meiosis is contingent upon symmetric nuclear division and asymmetric cytokinesis that plays an important role in the retention of maternal components necessary for cellular reprogramming and early embryo development. The failure nullifies all of the previous meiotic events including chromosome alignments and segregation. Beclin1, a mammalian ortholog of the Atg6/vaculolar protein sorting (Vps)-30 protein in yeast, has been reported to induce autophagy and apoptosis via phosphatidylinositol 3-kinase class III (PI3K-III).1 In particular, Beclin 1 was markedly increased in in vitro cultured foetal oocytes, suggesting autophagic and necrotic feature during meiotic progression.2 However, in this volume of Cell cycle, Jeong Su Oh and his colleagues provide a new insight into a novel role of Beclin-1 and its regulation during oocyte meiosis.3 Ablation of Beclin-1 led to cytokinetic abscission failure as a part of PI3K-III lipid-kinase complex but autophagy defect during meiotic maturation.3 This report raises questions about autophagy function of Beclin-1 and oocyte/embryo competency during maturation and pre-implantation development. Recently, it was reported that induction of autophagy treated with rapamycin (mTOR inhibitor) improved the nuclear and cytoplasmic maturation, and preimplantation development in porcine oocytes and embryos.4,5 Moreover, Beclin 1 and microtubule-associate protein 1-light chain 3 (LC3) were up-regulated in morphologically poor oocytes treated with rapamycin. Thus, it does not appear that previous studies support the results of Beclin-1 knock down experiments, abscission failure and nonautophogy defect in meiotic oocytes. However, the improvement may be attributed to an increase in Beclin-1 expression because developmental competency of oocytes treated with rapamycin during 22–42 hours of in vitro maturation (IVM) is comparable to those during 0–42 hours of IVM in porcine oocytes that took 30–48 hours for first polar body extrusion,6 implying that upregulated Beclin-1 in MI and MII staged porcine oocyte might lead to proper cytokinesis.
Understanding the regulation of PI3K-III complex including Beclin-1 is difficult in terms of cytokinesis and autophagy pathway. In the current Beclin-1 knock down study, the authors clarified that Beclin-1 is essential for the abscission via recruitment of ZFYVE26, a PI(3)P-binding protein, to the midbody, but not directly is involved in autophagy during meiotic cytokinesis using autophagy inhibitors such as 3-methyladenine and bafilomycin A1.
Disclosure of potential conflicts of interest No potential conflicts of interest were disclosed.
References [1] Kang R, et al. The Beclin 1 network regulates autophagy and apoptosis. Cell Death Differ 2011; 18(4):571–80; PMID:21311563; http://dx. doi.org/10.1038/cdd.2010.191 [2] De Felici M, et al. Cell death in fetal oocytes: many players for multiple pathways. Autophagy 2008; 4(2):240-2; PMID:18094606; http://dx. doi.org/10.4161/auto.5410 [3] You SY, et al. Beclin-1 knockdown shows abscission failure but not autophagy defect during oocyte meiotic maturation. Cell Cycle 2016; 15(12):1611–9; PMID:27149384; http://dx.doi.org/10.1080/15384101. 2016.1181235 [4] Song BS, et al. Induction of autophagy during in vitro maturation improves the nuclear and cytoplasmic maturation of porcine oocytes. Reprod Fertil Dev 2014; 26(7):974-81; PMID:23902659; http://dx.doi. org/10.1071/RD13106 [5] Lee J, et al. Rapamycin treatment during in vitro maturation of oocytes improves embryonic development after parthenogenesis and somatic cell nuclear transfer in pigs. J Vet Sci 2015; 16(3):373-80; PMID: 25797293; http://dx.doi.org/10.4142/jvs.2015.16.3.373 [6] Wang ZW, et al. Cytoplasmic Determination of Meiotic Spindle Size Revealed by a Unique Inter-Species Germinal Vesicle Transfer Model. Sci Rep 2016; 6:19827; PMID:26813698; http://dx.doi.org/10.1038/ srep19827
CONTACT Inchul Choi [email protected] Division of Animal and Dairy Sciences, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea. News and Views to: You SY, et al. Beclin-1 knockdown shows abscission failure but not autophagy defect during oocyte meiotic maturation. Cell Cycle 2016; 15(12):1611-9; PMID:27149384; http://dx.doi.org/10.1080/15384101.2016.1181235 © 2016 Taylor & Francis
