Apigenin inhibits larval growth of <i>Caenorhabditis elegans</i> through DAF-16 activation

Kawasaki, Ichiro,Jeong, Myung-Hwan,Oh, Bong-Kyeong,Shim, Yhong-Hee Elsevier 2010 FEBS letters Vol.584 No.16

<P><B>Abstract</B></P><P>Treatment of <I>Caenorhabditis elegans</I> with apigenin, 5,7,4′-trihydroxyflavone, induces larval growth inhibition. To understand the molecular basis of apigenin-induced larval growth inhibition, the effects of apigenin on DAF-16 activity were examined. DAF-16 was activated through nuclear translocation and the mRNA level of <I>sod-3</I>, one of the known DAF-16 target genes, was increased upon apigenin treatment. DAF-16 activity was required for the growth inhibition, since the larval growth retardation upon apigenin treatment was suppressed in <I>daf-16</I> mutants. These results indicate that apigenin acts as a stressor that activates DAF-16, which in turn inhibits larval growth.</P>

Regulation of sperm-specific proteins by IFE-1, a germline-specific homolog of eIF4E, in C. elegans

Kawasaki, Ichiro,Jeong, Myung-Hwan,Shim, Yhong-Hee Springer-Verlag 2011 Molecules and cells Vol.31 No.2

cdc-25.2, a C. elegans ortholog of cdc25, is required to promote oocyte maturation.

Kim, Jiyoung,Kawasaki, Ichiro,Shim, Yhong-Hee Cambridge University Press 2010 Journal of cell science Vol.123 No.6

<P>Cdc25 is an evolutionarily conserved protein phosphatase that promotes progression through the cell cycle. Some metazoans have multiple isoforms of Cdc25, which have distinct functions and different expression patterns during development. C. elegans has four cdc-25 genes. cdc-25.1 is required for germline mitotic proliferation. To determine if the other members of the cdc-25 family also contribute to regulation of cell division in the germ line, we examined phenotypes of loss-of-function mutants of the other cdc-25 family genes. We found that cdc-25.2 is also essential for germline development. cdc-25.2 homozygous mutant hermaphrodites exhibited sterility as a result of defects in oogenesis: mutant oocytes were arrested as endomitotic oocytes that were not fertilized successfully. Spermatogenesis and male germline development were not affected. Through genetic interaction studies, we found that CDC-25.2 functions upstream of maturation-promoting factor containing CDK-1 and CYB-3 to promote oocyte maturation by counteracting function of WEE-1.3. We propose that cdc-25 family members function as distinct but related cell cycle regulators to control diverse cell cycles in C. elegans germline development.</P>

LIN-23, an E3 Ubiquitin Ligase Component, Is Required for the Repression of CDC-25.2 Activity during Intestinal Development in Caenorhabditis elegans

Son, Miseol,Kawasaki, Ichiro,Oh, Bong-Kyeong,Shim, Yhong-Hee Korean Society for Molecular and Cellular Biology 2016 Molecules and cells Vol.39 No.11

Caenorhabditis elegans (C. elegans) utilizes two different cell-cycle modes, binucleations during the L1 larval stage and endoreduplications at four larval moltings, for its postembryonic intestinal development. Previous genetic studies indicated that CDC-25.2 is specifically required for binucleations at the L1 larval stage and is repressed before endoreduplications. Furthermore, LIN-23, the C. elegans ${\beta}$-TrCP ortholog, appears to function as a repressor of CDC-25.2 to prevent excess intestinal divisions. We previously reported that intestinal hyperplasia in lin-23(e1883) mutants was effectively suppressed by the RNAi depletion of cdc-25.2. Nevertheless, LIN-23 targeting CDC-25.2 for ubiquitination as a component of E3 ubiquitin ligase has not yet been tested. In this study, LIN-23 is shown to be the major E3 ubiquitin ligase component, recognizing CDC-25.2 to repress their activities for proper transition of cell-cycle modes during the C. elegans postembryonic intestinal development. In addition, for the first time that LIN-23 physically interacts with both CDC-25.1 and CDC-25.2 and facilitates ubiquitination for timely regulation of their activities during the intestinal development.

Caffeine Induces High Expression of cyp-35A Family Genes and Inhibits the Early Larval Development in Caenorhabditis elegans

Min, Hyemin,Kawasaki, Ichiro,Gong, Joomi,Shim, Yhong-Hee Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.3

Intake of caffeine during pregnancy can cause retardation of fetal development. Although the significant influence of caffeine on animal development is widely recognized, much remains unknown about its mode of action because of its pleiotropic effects on living organisms. In the present study, by using Caenorhabditis elegans as a model organism, the effects of caffeine on development were examined. Brood size, embryonic lethality, and percent larval development were investigated, and caffeine was found to inhibit the development of C. elegans at most of the stages in a dosage-dependent fashion. Upon treatment with 30 mM caffeine, the majority ($86.1{\pm}3.4%$) of the L1 larvae were irreversibly arrested without further development. In contrast, many of the late-stage larvae survived and grew to adults when exposed to the same 30 mM caffeine. These results suggest that early-stage larvae are more susceptible to caffeine than later-stage larvae. To understand the metabolic responses to caffeine treatment, the levels of expression of cytochrome P450 (cyp) genes were examined with or without caffeine treatment using comparative microarray, and it was found that the expression of 24 cyp genes was increased by more than 2-fold (p < 0.05). Among them, induction of the cyp-35A gene family was the most prominent. Interestingly, depletion of the cyp-35A family genes one-by-one or in combination through RNA interference resulted in partial rescue from early larval developmental arrest caused by caffeine treatment, suggesting that the high-level induction of cyp-35A family genes can be fatal to the development of early-stage larvae.

CDC-25.1 controls the rate of germline mitotic cell cycle by counteracting WEE-1.3 and by positively regulating CDK-1 in Caenorhabditis elegans.

Yoon, Sunghee,Kawasaki, Ichiro,Shim, Yhong-Hee Landes Bioscience 2012 Cell cycle Vol.11 No.7

<P>In Caenorhabditis elegans, cdc-25.1 loss-of-function mutants display a lack of germline proliferation. We found that the proliferation defect of cdc-25.1 mutants was suppressed by wee-1.3 RNAi. Further, among the seven cdk and seven cyclin homologs examined, cdk-1 and cyb-3 RNAi treatment caused the most severe germline proliferation defects in an rrf-1 mutant background, which were similar to those of the cdc-25.1 mutants. In addition, while RNAi of cyd-1 and cye-1 caused significant germline proliferation defects, RNAi of cdk-2 and cdk-4 did not. Compared with the number of germ nuclei in wee-1.3(RNAi) worms, the number in wee-1.3(RNAi);cdk-1(RNAi) and wee-1.3(RNAi);cyb-3(RNAi) worms further decreased to the level of cdk-1(RNAi) and cyb-3(RNAi) worms, respectively, indicating that cdk-1 and cyb-3 are epistatic and function downstream of cdc-25.1 and wee-1.3 in the control of the cell cycle. BrdU labeling of adult worms showed that, while 100% of the wild-type germ nuclei in the mitotic region incorporated BrdU when labeled for more than 12 h at 20C, a small fraction of the cdc-25.1 mutant germ nuclei failed to incorporate BrdU even when labeled for 68 h. These results indicate that CDC-25.1 is required for maintaining proper rate of germline mitotic cell cycle. We propose that CDC-25.1 regulates the rate of germline mitotic cell cycle by counteracting WEE-1.3 and by positively controlling CDK-1, which forms a complex primarily with CYB-3, but also possibly with CYD-1 and CYE-1.</P>

The B-type cyclin CYB-1 maintains the proper position and number of centrosomes during spermatogenesis in <i>Caenorhabditis elegans</i>

Yoon, Sunghee,Kawasaki, Ichiro,Shim, Yhong-Hee The Company of Biologists Ltd. 2017 Journal of cell science Vol. No.

<P>Depletion of cyb-1, a major B-type cyclin expressed during Caenorhabditis elegans spermatogenesis, causes a meiotic division arrest in diakinesis-stage spermatocytes with multiple and mispositioned centrosomes. Association of the two nuclear membrane proteins SUN-1 and ZYG-12 is essential for centrosome-nuclear envelope attachment. We found that depletion of sun-1 causes centrosome defects similar to those caused by cyb-1 depletion in diakinesis-stage spermatocytes. In addition, Ser8 and Ser43 residues in SUN-1 are dephosphorylated in cyb-1-depleted diakinesis-stage spermatocytes. Nevertheless, dephosphorylation of these residues was not sufficient to reproduce the cyb-1-related centrosome defects. We then found that the ZYG-12::GFP signal in the nuclear envelope was significantly reduced in the cyb-1-depleted diakinesis-stage spermatocytes. However, only mispositioned but not multiplied centrosomes were observed in zyg-12 mutant diakinesis-stage spermatocytes, suggesting that zyg-12 is not involved in the centrosome duplication at this stage. Our results suggest that CYB-1 functions to maintain proper positioning of centrosomes during spermatogenesis by regulating phosphorylation of SUN-1, which is possibly crucial for the association between SUN-1 and ZYG-12. This phosphorylation of SUN-1 may also regulate centrosome duplication independently of ZYG-12.</P>

Inhibition of overexpressed CDC-25.1 phosphatase activity by flavone in Caenorhabditis elegans

Kim, Koo-Seul,Kawasaki, Ichiro,Chong, Youhoon,Shim, Yhong-Hee Springer-Verlag 2009 Molecules and cells Vol.27 No.3

<P>We previously reported that flavone induces embryonic lethality in Caenorhabditis elegans, which appeared to be the result of cell cycle arrest during early embryogenesis. To test this possibility, here we examined whether flavone inhibits the activity of a key cell cycle regulator, CDC-25.1 in C. elegans. A gain-of-function cdc-25.1 mutant, rr31, which exhibits extra cell divisions in intestinal cells, was used to test the inhibitory effects of flavone on CDC-25 activity. Flavone inhibited the extra cell divisions of intestinal cells in rr31, and modifications of flavone reduced the inhibitory effects. The inhibitory effects of flavone on CDC-25.1 were partly, if not completely, due to transcriptional repression.</P>

A circulatory transcriptional regulation among <i>daf‐9, daf‐12</i>, and <i>daf‐16</i> mediates larval development upon cholesterol starvation in <i>Caenorhabditis elegans</i>†

Jeong, Myung‐,Hwan,Kawasaki, Ichiro,Shim, Yhong‐,Hee Wiley‐Liss, Inc. 2010 Developmental dynamics Vol.239 No.7

<P><B>Abstract</B></P><P><I>C. elegans</I> shows dauer‐like larvae formation upon cholesterol starvation (CS), but the genetic epistasis among abnormal dauer formation (<I>daf</I>) genes during the process remains unclear. To clarify the genetic interactions among <I>daf‐9, daf‐12</I>, and <I>daf‐16</I> in this process, mRNA levels of these genes upon CS were measured. CS increased the mRNA levels of <I>daf‐9, daf‐12</I>, and <I>daf‐16</I>. CS also induced DAF‐16 nuclear localization, which was positively and negatively regulated by DAF‐12 and DAF‐9 activities, respectively. Activated DAF‐16, a FOXO transcription factor, enhanced <I>daf‐12</I> but suppressed <I>daf‐9</I> expression, whereas DAF‐9 inhibited <I>daf‐12</I> expression. Concomitantly, CS‐induced larval arrest was regulated positively by DAF‐12 and DAF‐16, but negatively by DAF‐9. The larval arrest in <I>daf‐9</I> mutant was suppressed by <I>daf‐12</I> RNAi, placing DAF‐12 downstream of DAF‐9. These results altogether suggest that circulatory mutual regulation among <I>daf‐9, daf‐12</I>, and <I>daf‐16</I> at the expression level mediates cholesterol signal to control larval development upon CS. Developmental Dynamics 239:1931–1940, 2010. © 2010 Wiley‐Liss, Inc.</P>

Caffeine-induced food-avoidance behavior is mediated by neuroendocrine signals in Caenorhabditis elegans

( Hyemin Min ),( Esther Youn ),( Ichiro Kawasaki ),( Yhong-hee Shim ) 생화학분자생물학회(구 한국생화학분자생물학회) 2017 BMB Reports Vol.50 No.1

High-dose caffeine uptake is a developmental stressor and causes food-avoidance behavior (aversion phenotype) in C. elegans, but its mode of action is largely unknown. In this study, we investigated the molecular basis of the caffeine-induced aversion behavior in C. elegans. We found that aversion phenotype induced by 30 mM caffeine was mediated by JNK/MAPK pathway, serotonergic and dopaminergic neuroendocrine signals. In this process, the dopaminergic signaling appears to be the major pathway because the reduced aversion behavior in cat-2 mutants and mutants of JNK/MAPK pathway genes was significantly recovered by pretreatment with dopamine. RNAi depletion of hsp-16.2, a cytosolic chaperone, and cyp-35A family reduced the aversion phenotype, which was further reduced in cat-2 mutants, suggesting that dopaminergic signal is indeed dominantly required for the caffeine-induced food aversion. Our findings suggest that aversion behavior is a defense mechanism for worms to survive under the high-dose caffeine conditions. [BMB Reports 2017; 50(1): 31-36]