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The function of a spindle checkpoint gene bub-1 in C. elegans development.

Wang X, Liu M, Li W, Suh CD, Zhu Z, Jin Y, Fan Q - PLoS ONE (2009)

Bottom Line: In addition, bub-1(fw5 and fw8) mutants showed widespread effects on postembryonic development in many cell lineages.We found that bub-1 functioned maternally in several developmental lineages at the embryonic stage in C. elegans.Our results demonstrate a conserved role of bub-1 in cell-cycle regulation and reveal that C. elegans bub-1 is required both maternally and zygotically.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Peking University, Beijing, China.

ABSTRACT

Background: The serine/threonine kinase BUB1 (Budding Uninhibited by Benzimidazole 1) was originally identified in yeast as a checkpoint protein, based on its mutant's incapacity of delaying the cell cycle in response to loss of microtubules. Our understanding of its function is primarily from studies carried out in yeast S. cerevisiae. It has been shown that it is a component of the mitotic spindle checkpoint and regulates the separation of sister chromatids through its downstream molecules. However, its roles in multi-cellular organisms remain unclear.

Methods and findings: In nematode C. elegans, rapid cell divisions primarily occur in embryos and in germline of postembryonic larvae and adults. In addition, a select set of cells undergo a few rounds of cell division postembryonically. One common phenotype associated with impaired cell division is described as Stu (Sterile and Uncoordinated) [1], [2]. We conducted a genetic screen for zygotic mutants that displayed Stu phenotype in C. elegans. We isolated seven Stu mutants that fell into five complementation groups. We report here that two mutations, FanWang5 (fw5) and FanWang8 (fw8) affect the bub-1 gene, a homolog of yeast BUB1. Both mutant alleles of fw5 and fw8 exhibited variable behavioral defects, including developmental arrest, uncoordination and sterility. The number of postembryonically born neurons in the ventral cord decreased and their axon morphology was abnormal. Also, the decrease of neurons in the ventral cord phenotype could not be suppressed by a caspase-3 loss-of-function mutant. In addition, bub-1(fw5 and fw8) mutants showed widespread effects on postembryonic development in many cell lineages. We found that bub-1 functioned maternally in several developmental lineages at the embryonic stage in C. elegans. Studies in yeast have shown that BUB1 functions as a spindle checkpoint protein by regulating the anaphase promoting complex/cyclosome (APC/C). We performed double mutant analysis and observed that bub-1 genetically interacted with several downstream genes, including fzy-1/CDC20, mat-2/APC1 and emb-27/APC6.

Conclusions: Our results demonstrate a conserved role of bub-1 in cell-cycle regulation and reveal that C. elegans bub-1 is required both maternally and zygotically. Further, our genetic analysis is consistent with that the function of bub-1 in C. elegans is likely similar to its yeast and mammalian homologs.

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Weak Allele of fzy-1(h1983) Suppressed Neuron Decrease Phenotype of bub-1(fw8).(A) juIs14 [Pacr-2::GFP] strain visualizes A and B-type neurons, (B) bub-1(fw8) had less A and B type neuron. (C) fzy-1(h1983) did not affect A and B-type neuron fate. (D) fzy-1(h1983) could partially suppress bub-1(fw8) in neuron counting number. Arrows indicate some of the A and B-type neurons. The bar represents 50 µm. (E)Y axis shows the A and B-type neuron numbers (not including neurons in the head ganglia). Error bars represent standard deviation (the t-test compared to control fw8; juIs14: P<0.001).
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pone-0005912-g008: Weak Allele of fzy-1(h1983) Suppressed Neuron Decrease Phenotype of bub-1(fw8).(A) juIs14 [Pacr-2::GFP] strain visualizes A and B-type neurons, (B) bub-1(fw8) had less A and B type neuron. (C) fzy-1(h1983) did not affect A and B-type neuron fate. (D) fzy-1(h1983) could partially suppress bub-1(fw8) in neuron counting number. Arrows indicate some of the A and B-type neurons. The bar represents 50 µm. (E)Y axis shows the A and B-type neuron numbers (not including neurons in the head ganglia). Error bars represent standard deviation (the t-test compared to control fw8; juIs14: P<0.001).

Mentions: We used a transgenic GFP strain, juIs14 [33], to visualize the cholinergic DA, DB, VA, and VB neurons (Figure 8A). We observed a decreased number of neurons expressing GFP in the bub-1(fw8) mutant. Normally, embryonic-born DAs and DBs have commissural projections to the dorsal cord, while postembryonic-born VAs and VBs do not [38]. We found that the number of commissural projections to the dorsal cord was unchanged in the bub-1(fw8) mutant, and the axons of these neurons did not show any morphological defects (data not shown). Therefore, embryonic-born DAs and DBs were not affected, while most postembryonic-born VAs and VBs were missing in the bub-1(fw8) mutant.


The function of a spindle checkpoint gene bub-1 in C. elegans development.

Wang X, Liu M, Li W, Suh CD, Zhu Z, Jin Y, Fan Q - PLoS ONE (2009)

Weak Allele of fzy-1(h1983) Suppressed Neuron Decrease Phenotype of bub-1(fw8).(A) juIs14 [Pacr-2::GFP] strain visualizes A and B-type neurons, (B) bub-1(fw8) had less A and B type neuron. (C) fzy-1(h1983) did not affect A and B-type neuron fate. (D) fzy-1(h1983) could partially suppress bub-1(fw8) in neuron counting number. Arrows indicate some of the A and B-type neurons. The bar represents 50 µm. (E)Y axis shows the A and B-type neuron numbers (not including neurons in the head ganglia). Error bars represent standard deviation (the t-test compared to control fw8; juIs14: P<0.001).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2691579&req=5

pone-0005912-g008: Weak Allele of fzy-1(h1983) Suppressed Neuron Decrease Phenotype of bub-1(fw8).(A) juIs14 [Pacr-2::GFP] strain visualizes A and B-type neurons, (B) bub-1(fw8) had less A and B type neuron. (C) fzy-1(h1983) did not affect A and B-type neuron fate. (D) fzy-1(h1983) could partially suppress bub-1(fw8) in neuron counting number. Arrows indicate some of the A and B-type neurons. The bar represents 50 µm. (E)Y axis shows the A and B-type neuron numbers (not including neurons in the head ganglia). Error bars represent standard deviation (the t-test compared to control fw8; juIs14: P<0.001).
Mentions: We used a transgenic GFP strain, juIs14 [33], to visualize the cholinergic DA, DB, VA, and VB neurons (Figure 8A). We observed a decreased number of neurons expressing GFP in the bub-1(fw8) mutant. Normally, embryonic-born DAs and DBs have commissural projections to the dorsal cord, while postembryonic-born VAs and VBs do not [38]. We found that the number of commissural projections to the dorsal cord was unchanged in the bub-1(fw8) mutant, and the axons of these neurons did not show any morphological defects (data not shown). Therefore, embryonic-born DAs and DBs were not affected, while most postembryonic-born VAs and VBs were missing in the bub-1(fw8) mutant.

Bottom Line: In addition, bub-1(fw5 and fw8) mutants showed widespread effects on postembryonic development in many cell lineages.We found that bub-1 functioned maternally in several developmental lineages at the embryonic stage in C. elegans.Our results demonstrate a conserved role of bub-1 in cell-cycle regulation and reveal that C. elegans bub-1 is required both maternally and zygotically.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Peking University, Beijing, China.

ABSTRACT

Background: The serine/threonine kinase BUB1 (Budding Uninhibited by Benzimidazole 1) was originally identified in yeast as a checkpoint protein, based on its mutant's incapacity of delaying the cell cycle in response to loss of microtubules. Our understanding of its function is primarily from studies carried out in yeast S. cerevisiae. It has been shown that it is a component of the mitotic spindle checkpoint and regulates the separation of sister chromatids through its downstream molecules. However, its roles in multi-cellular organisms remain unclear.

Methods and findings: In nematode C. elegans, rapid cell divisions primarily occur in embryos and in germline of postembryonic larvae and adults. In addition, a select set of cells undergo a few rounds of cell division postembryonically. One common phenotype associated with impaired cell division is described as Stu (Sterile and Uncoordinated) [1], [2]. We conducted a genetic screen for zygotic mutants that displayed Stu phenotype in C. elegans. We isolated seven Stu mutants that fell into five complementation groups. We report here that two mutations, FanWang5 (fw5) and FanWang8 (fw8) affect the bub-1 gene, a homolog of yeast BUB1. Both mutant alleles of fw5 and fw8 exhibited variable behavioral defects, including developmental arrest, uncoordination and sterility. The number of postembryonically born neurons in the ventral cord decreased and their axon morphology was abnormal. Also, the decrease of neurons in the ventral cord phenotype could not be suppressed by a caspase-3 loss-of-function mutant. In addition, bub-1(fw5 and fw8) mutants showed widespread effects on postembryonic development in many cell lineages. We found that bub-1 functioned maternally in several developmental lineages at the embryonic stage in C. elegans. Studies in yeast have shown that BUB1 functions as a spindle checkpoint protein by regulating the anaphase promoting complex/cyclosome (APC/C). We performed double mutant analysis and observed that bub-1 genetically interacted with several downstream genes, including fzy-1/CDC20, mat-2/APC1 and emb-27/APC6.

Conclusions: Our results demonstrate a conserved role of bub-1 in cell-cycle regulation and reveal that C. elegans bub-1 is required both maternally and zygotically. Further, our genetic analysis is consistent with that the function of bub-1 in C. elegans is likely similar to its yeast and mammalian homologs.

Show MeSH
Related in: MedlinePlus