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Centrosome/Cell cycle uncoupling and elimination in the endoreduplicating intestinal cells of C. elegans.

Lu Y, Roy R - PLoS ONE (2014)

Bottom Line: The centrioles then become refractory to S phase regulators that would normally promote duplication during the first endocycle, after which they are eliminated during the L2 stage.Furthermore, we show that SPD-2 plays a central role in the numeral regulation of centrioles as a potential target of CDK activity.On the other hand, the phosphorylation on SPD-2 by Polo-like kinase, the transcriptional regulation of genes that affect centriole biogenesis, and the ubiquitin/proteasome degradation pathway, contribute collectively to the final elimination of the centrioles during the L2 stage.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, The Developmental Biology Research Initiative, McGill University, Montreal, Quebec, Canada.

ABSTRACT
The centrosome cycle is most often coordinated with mitotic cell division through the activity of various essential cell cycle regulators, consequently ensuring that the centriole is duplicated once, and only once, per cell cycle. However, this coupling can be altered in specific developmental contexts; for example, multi-ciliated cells generate hundreds of centrioles without any S-phase requirement for their biogenesis, while Drosophila follicle cells eliminate their centrosomes as they begin to endoreduplicate. In order to better understand how the centrosome cycle and the cell cycle are coordinated in a developmental context we use the endoreduplicating intestinal cell lineage of C. elegans to address how novel variations of the cell cycle impact this important process. In C. elegans, the larval intestinal cells undergo one nuclear division without subsequent cytokinesis, followed by four endocycles that are characterized by successive rounds of S-phase. We monitored the levels of centriolar/centrosomal markers and found that centrosomes lose their pericentriolar material following the nuclear division that occurs during the L1 stage and is thereafter never re-gained. The centrioles then become refractory to S phase regulators that would normally promote duplication during the first endocycle, after which they are eliminated during the L2 stage. Furthermore, we show that SPD-2 plays a central role in the numeral regulation of centrioles as a potential target of CDK activity. On the other hand, the phosphorylation on SPD-2 by Polo-like kinase, the transcriptional regulation of genes that affect centriole biogenesis, and the ubiquitin/proteasome degradation pathway, contribute collectively to the final elimination of the centrioles during the L2 stage.

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Centrioles are eliminated in many somatic cells of C. elegans following the completion of mitosis.(A–D) Larvae expressing intestine-specific elt-2::GFP were stained with DAPI (red) and anti-GFP (green) [44]. (A and C) show anti-GFP signal alone. Asterisks mark the intestinal nuclei. (E) A schematic diagram shows the relative position of intestinal nuclei before and after the nuclear division at the L1/L2 transition. Lineage brackets indicate two daughter cells from a common intestinal cell mother. Green ovals, intestinal nuclei. (F) A representative map of the postembryonic intestinal cell lineage: C refers to haploid DNA content in the nuclei. L1–L4 on the y axis indicate developmental timing showing the different larval stages; In, intestinal cells [29]–[30]. (G and H) Animals co-expressing the adherens junction marker ajm-1::GFP and seam cell marker scm-1::GFP [76] were stained with DAPI (red) and anti-GFP (green). (G) shows anti-GFP signal alone. Lineage brackets indicate two daughter cells from a common V cell mother. hyp7 and the arrow marks a hyp7 nucleus. A, anterior; P, posterior. (I) A schematic diagram summarizes the relative positions of V cells shown in (G) and (H). (J–K′) SPD-2::GFP was observed in the seam cells before, but not after the final cell division. White rectangles indicate the seam cells from the V1 lineage and the insets represent the magnified views of GFP signal in the corresponding white rectangles in J and K. J′ and K′ show the focal plane of the cuticle to indicate the presence or absence of adult alae (which indicates terminally differentiated seam cells in J and K), respectively. (L) A schematic diagram indicates the cross section view of a C. elegans body. Red spindles, V cell nuclei. The red italic letters and the black arrows together indicate the focal planes in the corresponding micrographs. (M) A map of the V1 lineage. The parallel lines indicate the alae/terminal differentiation. (N and O) SPD-2::GFP can be seen in the vulva cell lineage (P6.p) before (N) but not after (O) the completion of cell division. White rectangles highlight P6.p descendants and the insets represent the magnified views of GFP signal in the corresponding white rectangles. (P) A schematic diagram highlights later P6.p cell divisions a-anterior; p-posterior; l-left; r-right. Blue ovals depict nuclei of P6.p descendants. Black arrows point out the boxed nuclei in (N) or (O). (Q) A map of the P6.p cell lineage. The arrowheads indicate the SPD-2 foci. Scale bar, 5 µm. Red italicized letters in the lineage maps F, M, and Q show the precise time when the cells represented in the corresponding panels (non-italicized bold letters) were imaged.
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pone-0110958-g001: Centrioles are eliminated in many somatic cells of C. elegans following the completion of mitosis.(A–D) Larvae expressing intestine-specific elt-2::GFP were stained with DAPI (red) and anti-GFP (green) [44]. (A and C) show anti-GFP signal alone. Asterisks mark the intestinal nuclei. (E) A schematic diagram shows the relative position of intestinal nuclei before and after the nuclear division at the L1/L2 transition. Lineage brackets indicate two daughter cells from a common intestinal cell mother. Green ovals, intestinal nuclei. (F) A representative map of the postembryonic intestinal cell lineage: C refers to haploid DNA content in the nuclei. L1–L4 on the y axis indicate developmental timing showing the different larval stages; In, intestinal cells [29]–[30]. (G and H) Animals co-expressing the adherens junction marker ajm-1::GFP and seam cell marker scm-1::GFP [76] were stained with DAPI (red) and anti-GFP (green). (G) shows anti-GFP signal alone. Lineage brackets indicate two daughter cells from a common V cell mother. hyp7 and the arrow marks a hyp7 nucleus. A, anterior; P, posterior. (I) A schematic diagram summarizes the relative positions of V cells shown in (G) and (H). (J–K′) SPD-2::GFP was observed in the seam cells before, but not after the final cell division. White rectangles indicate the seam cells from the V1 lineage and the insets represent the magnified views of GFP signal in the corresponding white rectangles in J and K. J′ and K′ show the focal plane of the cuticle to indicate the presence or absence of adult alae (which indicates terminally differentiated seam cells in J and K), respectively. (L) A schematic diagram indicates the cross section view of a C. elegans body. Red spindles, V cell nuclei. The red italic letters and the black arrows together indicate the focal planes in the corresponding micrographs. (M) A map of the V1 lineage. The parallel lines indicate the alae/terminal differentiation. (N and O) SPD-2::GFP can be seen in the vulva cell lineage (P6.p) before (N) but not after (O) the completion of cell division. White rectangles highlight P6.p descendants and the insets represent the magnified views of GFP signal in the corresponding white rectangles. (P) A schematic diagram highlights later P6.p cell divisions a-anterior; p-posterior; l-left; r-right. Blue ovals depict nuclei of P6.p descendants. Black arrows point out the boxed nuclei in (N) or (O). (Q) A map of the P6.p cell lineage. The arrowheads indicate the SPD-2 foci. Scale bar, 5 µm. Red italicized letters in the lineage maps F, M, and Q show the precise time when the cells represented in the corresponding panels (non-italicized bold letters) were imaged.

Mentions: In C. elegans both the intestine and the lateral hypodermal cells execute endocycles during larval development, giving rise to polyploid cells in the adult [29]. The intestinal nuclei undergo a single round of nuclear division in the absence of cytokinesis at the end of the first larval stage (L1) to become binucleate (Figure 1A–1E), followed by a single endocycle at the end of each larval stage [29] (Figure 1F). In the hypodermal V cell lineage, an anterior daughter cell is generated that undergoes endoreduplication and will eventually fuse with the hyp7 syncytium, while the posterior seam cell daughter will divide once during the L1 (Figure 1G–1I, 1M). After an equational division at the L1/L2 transition the V cell lineage repeats its L1 pattern of cell division in each subsequent larval stage, yielding one anterior endocycling cell that fuses with the hypodermis and its sister that will continue to execute a mitotic stem cell division [29] (Figure 1M).


Centrosome/Cell cycle uncoupling and elimination in the endoreduplicating intestinal cells of C. elegans.

Lu Y, Roy R - PLoS ONE (2014)

Centrioles are eliminated in many somatic cells of C. elegans following the completion of mitosis.(A–D) Larvae expressing intestine-specific elt-2::GFP were stained with DAPI (red) and anti-GFP (green) [44]. (A and C) show anti-GFP signal alone. Asterisks mark the intestinal nuclei. (E) A schematic diagram shows the relative position of intestinal nuclei before and after the nuclear division at the L1/L2 transition. Lineage brackets indicate two daughter cells from a common intestinal cell mother. Green ovals, intestinal nuclei. (F) A representative map of the postembryonic intestinal cell lineage: C refers to haploid DNA content in the nuclei. L1–L4 on the y axis indicate developmental timing showing the different larval stages; In, intestinal cells [29]–[30]. (G and H) Animals co-expressing the adherens junction marker ajm-1::GFP and seam cell marker scm-1::GFP [76] were stained with DAPI (red) and anti-GFP (green). (G) shows anti-GFP signal alone. Lineage brackets indicate two daughter cells from a common V cell mother. hyp7 and the arrow marks a hyp7 nucleus. A, anterior; P, posterior. (I) A schematic diagram summarizes the relative positions of V cells shown in (G) and (H). (J–K′) SPD-2::GFP was observed in the seam cells before, but not after the final cell division. White rectangles indicate the seam cells from the V1 lineage and the insets represent the magnified views of GFP signal in the corresponding white rectangles in J and K. J′ and K′ show the focal plane of the cuticle to indicate the presence or absence of adult alae (which indicates terminally differentiated seam cells in J and K), respectively. (L) A schematic diagram indicates the cross section view of a C. elegans body. Red spindles, V cell nuclei. The red italic letters and the black arrows together indicate the focal planes in the corresponding micrographs. (M) A map of the V1 lineage. The parallel lines indicate the alae/terminal differentiation. (N and O) SPD-2::GFP can be seen in the vulva cell lineage (P6.p) before (N) but not after (O) the completion of cell division. White rectangles highlight P6.p descendants and the insets represent the magnified views of GFP signal in the corresponding white rectangles. (P) A schematic diagram highlights later P6.p cell divisions a-anterior; p-posterior; l-left; r-right. Blue ovals depict nuclei of P6.p descendants. Black arrows point out the boxed nuclei in (N) or (O). (Q) A map of the P6.p cell lineage. The arrowheads indicate the SPD-2 foci. Scale bar, 5 µm. Red italicized letters in the lineage maps F, M, and Q show the precise time when the cells represented in the corresponding panels (non-italicized bold letters) were imaged.
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pone-0110958-g001: Centrioles are eliminated in many somatic cells of C. elegans following the completion of mitosis.(A–D) Larvae expressing intestine-specific elt-2::GFP were stained with DAPI (red) and anti-GFP (green) [44]. (A and C) show anti-GFP signal alone. Asterisks mark the intestinal nuclei. (E) A schematic diagram shows the relative position of intestinal nuclei before and after the nuclear division at the L1/L2 transition. Lineage brackets indicate two daughter cells from a common intestinal cell mother. Green ovals, intestinal nuclei. (F) A representative map of the postembryonic intestinal cell lineage: C refers to haploid DNA content in the nuclei. L1–L4 on the y axis indicate developmental timing showing the different larval stages; In, intestinal cells [29]–[30]. (G and H) Animals co-expressing the adherens junction marker ajm-1::GFP and seam cell marker scm-1::GFP [76] were stained with DAPI (red) and anti-GFP (green). (G) shows anti-GFP signal alone. Lineage brackets indicate two daughter cells from a common V cell mother. hyp7 and the arrow marks a hyp7 nucleus. A, anterior; P, posterior. (I) A schematic diagram summarizes the relative positions of V cells shown in (G) and (H). (J–K′) SPD-2::GFP was observed in the seam cells before, but not after the final cell division. White rectangles indicate the seam cells from the V1 lineage and the insets represent the magnified views of GFP signal in the corresponding white rectangles in J and K. J′ and K′ show the focal plane of the cuticle to indicate the presence or absence of adult alae (which indicates terminally differentiated seam cells in J and K), respectively. (L) A schematic diagram indicates the cross section view of a C. elegans body. Red spindles, V cell nuclei. The red italic letters and the black arrows together indicate the focal planes in the corresponding micrographs. (M) A map of the V1 lineage. The parallel lines indicate the alae/terminal differentiation. (N and O) SPD-2::GFP can be seen in the vulva cell lineage (P6.p) before (N) but not after (O) the completion of cell division. White rectangles highlight P6.p descendants and the insets represent the magnified views of GFP signal in the corresponding white rectangles. (P) A schematic diagram highlights later P6.p cell divisions a-anterior; p-posterior; l-left; r-right. Blue ovals depict nuclei of P6.p descendants. Black arrows point out the boxed nuclei in (N) or (O). (Q) A map of the P6.p cell lineage. The arrowheads indicate the SPD-2 foci. Scale bar, 5 µm. Red italicized letters in the lineage maps F, M, and Q show the precise time when the cells represented in the corresponding panels (non-italicized bold letters) were imaged.
Mentions: In C. elegans both the intestine and the lateral hypodermal cells execute endocycles during larval development, giving rise to polyploid cells in the adult [29]. The intestinal nuclei undergo a single round of nuclear division in the absence of cytokinesis at the end of the first larval stage (L1) to become binucleate (Figure 1A–1E), followed by a single endocycle at the end of each larval stage [29] (Figure 1F). In the hypodermal V cell lineage, an anterior daughter cell is generated that undergoes endoreduplication and will eventually fuse with the hyp7 syncytium, while the posterior seam cell daughter will divide once during the L1 (Figure 1G–1I, 1M). After an equational division at the L1/L2 transition the V cell lineage repeats its L1 pattern of cell division in each subsequent larval stage, yielding one anterior endocycling cell that fuses with the hypodermis and its sister that will continue to execute a mitotic stem cell division [29] (Figure 1M).

Bottom Line: The centrioles then become refractory to S phase regulators that would normally promote duplication during the first endocycle, after which they are eliminated during the L2 stage.Furthermore, we show that SPD-2 plays a central role in the numeral regulation of centrioles as a potential target of CDK activity.On the other hand, the phosphorylation on SPD-2 by Polo-like kinase, the transcriptional regulation of genes that affect centriole biogenesis, and the ubiquitin/proteasome degradation pathway, contribute collectively to the final elimination of the centrioles during the L2 stage.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, The Developmental Biology Research Initiative, McGill University, Montreal, Quebec, Canada.

ABSTRACT
The centrosome cycle is most often coordinated with mitotic cell division through the activity of various essential cell cycle regulators, consequently ensuring that the centriole is duplicated once, and only once, per cell cycle. However, this coupling can be altered in specific developmental contexts; for example, multi-ciliated cells generate hundreds of centrioles without any S-phase requirement for their biogenesis, while Drosophila follicle cells eliminate their centrosomes as they begin to endoreduplicate. In order to better understand how the centrosome cycle and the cell cycle are coordinated in a developmental context we use the endoreduplicating intestinal cell lineage of C. elegans to address how novel variations of the cell cycle impact this important process. In C. elegans, the larval intestinal cells undergo one nuclear division without subsequent cytokinesis, followed by four endocycles that are characterized by successive rounds of S-phase. We monitored the levels of centriolar/centrosomal markers and found that centrosomes lose their pericentriolar material following the nuclear division that occurs during the L1 stage and is thereafter never re-gained. The centrioles then become refractory to S phase regulators that would normally promote duplication during the first endocycle, after which they are eliminated during the L2 stage. Furthermore, we show that SPD-2 plays a central role in the numeral regulation of centrioles as a potential target of CDK activity. On the other hand, the phosphorylation on SPD-2 by Polo-like kinase, the transcriptional regulation of genes that affect centriole biogenesis, and the ubiquitin/proteasome degradation pathway, contribute collectively to the final elimination of the centrioles during the L2 stage.

Show MeSH
Related in: MedlinePlus