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Dynamics of endoreplication during Drosophila posterior scutellar macrochaete development.

Kawamori A, Shimaji K, Yamaguchi M - PLoS ONE (2012)

Bottom Line: We also found that the timing of endoreplication differs, depending on the type of macrochaete.Moreover, endocycling in shaft cells of both the left and right sides of pSC bristle lineages occurs in the same pattern, indicating that the process is synchronized for specific types of macrochaete.Our findings suggest that endocycling in macrochaete cell lineages can be a model for understanding mechanisms of endoreplication at the single-cell level.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Biology, Kyoto Institute of Technology, Sakyo-ku, Kyoto, Japan.

ABSTRACT
Endoreplication is a variant type of DNA replication, consisting only of alternating G1 and S phases. Many types of Drosophila tissues undergo endoreplication. However, the timing and the extent to which a single endocycling macrochaete undergoes temporally programmed endoreplication during development are unclear. Here, we focused on the dynamics of endoreplication during posterior scutellar (pSC) macrochaete development. Quantitative analyses of C values in shaft cells and socket cells revealed a gradual rise from 8C and 4C at 8 hours after pupal formation (APF) to 72C and 24C at 29 hours APF, respectively. The validity of the values was further confirmed by the measurement of DNA content with a confocal laser microscope. BrdU incorporation assays demonstrated that shaft cells undergo four rounds of endoreplication from 18 to 29.5 hours APF. In contrast, socket cells undergo two rounds of endoreplication during the same period. Statistical analyses showed that the theoretical C values, based on BrdU assays, nearly coincide with the actually measured C values in socket cells, but not in shaft cells after 22 hours APF. These analyses suggest that socket cells undergo two rounds of endoreplication. However, the mechanism of endoreplication in the shaft cells may change from 22 hours APF, suggesting the possibility that shaft cells undergo two or four rounds of endoreplication during the periods. We also found that the timing of endoreplication differs, depending on the type of macrochaete. Moreover, endocycling in shaft cells of both the left and right sides of pSC bristle lineages occurs in the same pattern, indicating that the process is synchronized for specific types of macrochaete. Our findings suggest that endocycling in macrochaete cell lineages can be a model for understanding mechanisms of endoreplication at the single-cell level.

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Dynamics of nuclear growth in pSC shaft cells from 8 to 29 hours APF.(A–O) Images of pSC shaft cells from 8 to 29 hours APF. Pupae with the A101-lacZ /+ genotype were grown till 8(n = 6), 12(n = 3), 18(n = 8), 20(n = 11), 21(n = 8), 22(n = 8), 23(n = 3), 24(n = 7), 25(n = 5), 26(n = 11), 27(n = 6), 29 hours APF (n = 7) and dissected thoraxes were stained with anti-lacZ and DAPI. Arrows indicate socket cell nuclei and arrowheads shaft cell nuclei. (P) Dynamics of nuclear growth in a pSC shaft cell from 8 to 29 hours APF. The Y axis indicates the section area of the shaft cell nucleus. Significant differences in mean values at each time point to those of adjacent time points were set at *P<0.05, **P<0.01 and ***P<0.001. (Q) Illustration of 22 macrochaetes on left and right sides of an adult thorax. pSC, posterior scutellar; aSC, anterior scutellar; pDC, posterior dorsocentral; aDC, anterior dorsocentral; pPA, posterior postalar; aPA, anterior postalar; pSA, posterior supraalar; aSA, anterior supraalar; pNP, posterior notopleural;, aNP, anterior notopleural; PC, presutural.
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pone-0038714-g001: Dynamics of nuclear growth in pSC shaft cells from 8 to 29 hours APF.(A–O) Images of pSC shaft cells from 8 to 29 hours APF. Pupae with the A101-lacZ /+ genotype were grown till 8(n = 6), 12(n = 3), 18(n = 8), 20(n = 11), 21(n = 8), 22(n = 8), 23(n = 3), 24(n = 7), 25(n = 5), 26(n = 11), 27(n = 6), 29 hours APF (n = 7) and dissected thoraxes were stained with anti-lacZ and DAPI. Arrows indicate socket cell nuclei and arrowheads shaft cell nuclei. (P) Dynamics of nuclear growth in a pSC shaft cell from 8 to 29 hours APF. The Y axis indicates the section area of the shaft cell nucleus. Significant differences in mean values at each time point to those of adjacent time points were set at *P<0.05, **P<0.01 and ***P<0.001. (Q) Illustration of 22 macrochaetes on left and right sides of an adult thorax. pSC, posterior scutellar; aSC, anterior scutellar; pDC, posterior dorsocentral; aDC, anterior dorsocentral; pPA, posterior postalar; aPA, anterior postalar; pSA, posterior supraalar; aSA, anterior supraalar; pNP, posterior notopleural;, aNP, anterior notopleural; PC, presutural.

Mentions: In Drosophila the shaft and socket cells of sensory bristles, the macrochaetes and microchaetes utilize endocycling. The macrochaete is a type of large mechanosensory bristle on the Drosophila adult thorax which consists of four differentiated cells (shaft, socket, sheath and neuron). There are 11 macrochaetes (Fig. 1Q) and more than 200 microchaetes [16]. The differentiation of the sensory organ precursors (SOPs) of macrochaetes occurs within proneural clusters (PNCs) at the third instar larval stage [17]. The differentiated SOP of a bristle asymmetrically divides to produce a PIIa cell and a PIIb cell. The PIIa cell divides to give rise to a shaft cell and a socket cell. The PIIb cell divides twice to produce a glial cell, a sheath cell and a neuron [18]–[21]. The glial cell undergoes programmed cell death shortly after its birth [20]. During macrochaete development, each SOP differentiates at different times at different positions of the wing discs. For example, SOPs of single posterior scutellar (pSC) bristles differentiate 30 hours before pupal formation (BPF) [17]. The onset of asymmetric cell division in the pSC cell lineage appears to occur just before pupal formation and end around 3 to 5 hours APF [17]. After cell differentiation, both the shaft cell and the socket cell undergo a few rounds of replication in the case of the microchaete cell lineage [21]–[23]. However, little is known about how much endoreplication occurs in shaft and socket cells in the macrochaete cell lineage.


Dynamics of endoreplication during Drosophila posterior scutellar macrochaete development.

Kawamori A, Shimaji K, Yamaguchi M - PLoS ONE (2012)

Dynamics of nuclear growth in pSC shaft cells from 8 to 29 hours APF.(A–O) Images of pSC shaft cells from 8 to 29 hours APF. Pupae with the A101-lacZ /+ genotype were grown till 8(n = 6), 12(n = 3), 18(n = 8), 20(n = 11), 21(n = 8), 22(n = 8), 23(n = 3), 24(n = 7), 25(n = 5), 26(n = 11), 27(n = 6), 29 hours APF (n = 7) and dissected thoraxes were stained with anti-lacZ and DAPI. Arrows indicate socket cell nuclei and arrowheads shaft cell nuclei. (P) Dynamics of nuclear growth in a pSC shaft cell from 8 to 29 hours APF. The Y axis indicates the section area of the shaft cell nucleus. Significant differences in mean values at each time point to those of adjacent time points were set at *P<0.05, **P<0.01 and ***P<0.001. (Q) Illustration of 22 macrochaetes on left and right sides of an adult thorax. pSC, posterior scutellar; aSC, anterior scutellar; pDC, posterior dorsocentral; aDC, anterior dorsocentral; pPA, posterior postalar; aPA, anterior postalar; pSA, posterior supraalar; aSA, anterior supraalar; pNP, posterior notopleural;, aNP, anterior notopleural; PC, presutural.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3368872&req=5

pone-0038714-g001: Dynamics of nuclear growth in pSC shaft cells from 8 to 29 hours APF.(A–O) Images of pSC shaft cells from 8 to 29 hours APF. Pupae with the A101-lacZ /+ genotype were grown till 8(n = 6), 12(n = 3), 18(n = 8), 20(n = 11), 21(n = 8), 22(n = 8), 23(n = 3), 24(n = 7), 25(n = 5), 26(n = 11), 27(n = 6), 29 hours APF (n = 7) and dissected thoraxes were stained with anti-lacZ and DAPI. Arrows indicate socket cell nuclei and arrowheads shaft cell nuclei. (P) Dynamics of nuclear growth in a pSC shaft cell from 8 to 29 hours APF. The Y axis indicates the section area of the shaft cell nucleus. Significant differences in mean values at each time point to those of adjacent time points were set at *P<0.05, **P<0.01 and ***P<0.001. (Q) Illustration of 22 macrochaetes on left and right sides of an adult thorax. pSC, posterior scutellar; aSC, anterior scutellar; pDC, posterior dorsocentral; aDC, anterior dorsocentral; pPA, posterior postalar; aPA, anterior postalar; pSA, posterior supraalar; aSA, anterior supraalar; pNP, posterior notopleural;, aNP, anterior notopleural; PC, presutural.
Mentions: In Drosophila the shaft and socket cells of sensory bristles, the macrochaetes and microchaetes utilize endocycling. The macrochaete is a type of large mechanosensory bristle on the Drosophila adult thorax which consists of four differentiated cells (shaft, socket, sheath and neuron). There are 11 macrochaetes (Fig. 1Q) and more than 200 microchaetes [16]. The differentiation of the sensory organ precursors (SOPs) of macrochaetes occurs within proneural clusters (PNCs) at the third instar larval stage [17]. The differentiated SOP of a bristle asymmetrically divides to produce a PIIa cell and a PIIb cell. The PIIa cell divides to give rise to a shaft cell and a socket cell. The PIIb cell divides twice to produce a glial cell, a sheath cell and a neuron [18]–[21]. The glial cell undergoes programmed cell death shortly after its birth [20]. During macrochaete development, each SOP differentiates at different times at different positions of the wing discs. For example, SOPs of single posterior scutellar (pSC) bristles differentiate 30 hours before pupal formation (BPF) [17]. The onset of asymmetric cell division in the pSC cell lineage appears to occur just before pupal formation and end around 3 to 5 hours APF [17]. After cell differentiation, both the shaft cell and the socket cell undergo a few rounds of replication in the case of the microchaete cell lineage [21]–[23]. However, little is known about how much endoreplication occurs in shaft and socket cells in the macrochaete cell lineage.

Bottom Line: We also found that the timing of endoreplication differs, depending on the type of macrochaete.Moreover, endocycling in shaft cells of both the left and right sides of pSC bristle lineages occurs in the same pattern, indicating that the process is synchronized for specific types of macrochaete.Our findings suggest that endocycling in macrochaete cell lineages can be a model for understanding mechanisms of endoreplication at the single-cell level.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Biology, Kyoto Institute of Technology, Sakyo-ku, Kyoto, Japan.

ABSTRACT
Endoreplication is a variant type of DNA replication, consisting only of alternating G1 and S phases. Many types of Drosophila tissues undergo endoreplication. However, the timing and the extent to which a single endocycling macrochaete undergoes temporally programmed endoreplication during development are unclear. Here, we focused on the dynamics of endoreplication during posterior scutellar (pSC) macrochaete development. Quantitative analyses of C values in shaft cells and socket cells revealed a gradual rise from 8C and 4C at 8 hours after pupal formation (APF) to 72C and 24C at 29 hours APF, respectively. The validity of the values was further confirmed by the measurement of DNA content with a confocal laser microscope. BrdU incorporation assays demonstrated that shaft cells undergo four rounds of endoreplication from 18 to 29.5 hours APF. In contrast, socket cells undergo two rounds of endoreplication during the same period. Statistical analyses showed that the theoretical C values, based on BrdU assays, nearly coincide with the actually measured C values in socket cells, but not in shaft cells after 22 hours APF. These analyses suggest that socket cells undergo two rounds of endoreplication. However, the mechanism of endoreplication in the shaft cells may change from 22 hours APF, suggesting the possibility that shaft cells undergo two or four rounds of endoreplication during the periods. We also found that the timing of endoreplication differs, depending on the type of macrochaete. Moreover, endocycling in shaft cells of both the left and right sides of pSC bristle lineages occurs in the same pattern, indicating that the process is synchronized for specific types of macrochaete. Our findings suggest that endocycling in macrochaete cell lineages can be a model for understanding mechanisms of endoreplication at the single-cell level.

Show MeSH
Related in: MedlinePlus