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Metaphase to anaphase (mat) transition-defective mutants in Caenorhabditis elegans.

Golden A, Sadler PL, Wallenfang MR, Schumacher JM, Hamill DR, Bates G, Bowerman B, Seydoux G, Shakes DC - J. Cell Biol. (2000)

Bottom Line: Analogous mitotic defects cause M phase delays in mitotic germline proliferation.We have named this class of mutants "mat" for metaphase to anaphase transition defective.These mutants, representing six different complementation groups, all map near genes that encode subunits of the anaphase promoting complex or cyclosome, and, here, we show that one of the genes, emb-27, encodes the C. elegans CDC16 ortholog.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.

ABSTRACT
The metaphase to anaphase transition is a critical stage of the eukaryotic cell cycle, and, thus, it is highly regulated. Errors during this transition can lead to chromosome segregation defects and death of the organism. In genetic screens for temperature-sensitive maternal effect embryonic lethal (Mel) mutants, we have identified 32 mutants in the nematode Caenorhabditis elegans in which fertilized embryos arrest as one-cell embryos. In these mutant embryos, the oocyte chromosomes arrest in metaphase of meiosis I without transitioning to anaphase or producing polar bodies. An additional block in M phase exit is evidenced by the failure to form pronuclei and the persistence of phosphohistone H3 and MPM-2 antibody staining. Spermatocyte meiosis is also perturbed; primary spermatocytes arrest in metaphase of meiosis I and fail to produce secondary spermatocytes. Analogous mitotic defects cause M phase delays in mitotic germline proliferation. We have named this class of mutants "mat" for metaphase to anaphase transition defective. These mutants, representing six different complementation groups, all map near genes that encode subunits of the anaphase promoting complex or cyclosome, and, here, we show that one of the genes, emb-27, encodes the C. elegans CDC16 ortholog.

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Related in: MedlinePlus

Tubulin and DAPI localization in wild-type and mutant spermatocytes. Shown in A is a depiction of wild-type spermatogenesis. After nuclear envelope breakdown, the chromosomes of primary (1°) spermatocytes congress to form a meiosis I metaphase plate. The first meiotic division yields two secondary (2°) spermatocytes, which can either be separated or remain attached through a cytoplasmic connection due to incomplete cytokinesis. Secondary spermatocytes subsequently undergo a polarized budding division during which two haploid sperm separate from a central residual body. (B) A wild-type male germline squashed in the presence of Hoechst dye 33342 and observed by DIC and UV epifluorescence. All meiotic stages can be seen. Primaries (1°) and secondaries (2°) can be distinguished by size (B). A budding figure (BF) is visible in the lower right corner. Haploid sperm (S) and residual bodies (RB) are also indicated. (C) A sperm spread from a mat-3(ax82) male lacks 2° spermatocytes, but contains many anucleate sperm. Abnormal budding figures are also present in which all the chromosomes remain in the center of the developing residual body. Staining with anti–α-tubulin antibody (E, G, I, and K) and DAPI (D, F, H, and L) reveals the underlying spindle structures in these sperm spreads (E, G, I, and K). In wild-type sperm spreads, distinctive meiotic spindles are apparent in 1° and 2° spermatocytes and in budding figures (D and E). A magnified view of a wild-type meiotic spindle is shown in (I) with its corresponding DAPI image (H). In the mat mutants, normal meiosis I–like spindles form, but anaphase figures are never observed (F, G, J, and K). The diameter of a primary spermatocyte equals 12 μm.
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Figure 7: Tubulin and DAPI localization in wild-type and mutant spermatocytes. Shown in A is a depiction of wild-type spermatogenesis. After nuclear envelope breakdown, the chromosomes of primary (1°) spermatocytes congress to form a meiosis I metaphase plate. The first meiotic division yields two secondary (2°) spermatocytes, which can either be separated or remain attached through a cytoplasmic connection due to incomplete cytokinesis. Secondary spermatocytes subsequently undergo a polarized budding division during which two haploid sperm separate from a central residual body. (B) A wild-type male germline squashed in the presence of Hoechst dye 33342 and observed by DIC and UV epifluorescence. All meiotic stages can be seen. Primaries (1°) and secondaries (2°) can be distinguished by size (B). A budding figure (BF) is visible in the lower right corner. Haploid sperm (S) and residual bodies (RB) are also indicated. (C) A sperm spread from a mat-3(ax82) male lacks 2° spermatocytes, but contains many anucleate sperm. Abnormal budding figures are also present in which all the chromosomes remain in the center of the developing residual body. Staining with anti–α-tubulin antibody (E, G, I, and K) and DAPI (D, F, H, and L) reveals the underlying spindle structures in these sperm spreads (E, G, I, and K). In wild-type sperm spreads, distinctive meiotic spindles are apparent in 1° and 2° spermatocytes and in budding figures (D and E). A magnified view of a wild-type meiotic spindle is shown in (I) with its corresponding DAPI image (H). In the mat mutants, normal meiosis I–like spindles form, but anaphase figures are never observed (F, G, J, and K). The diameter of a primary spermatocyte equals 12 μm.

Mentions: In C. elegans, the first meiotic division of the oocyte takes place on an acentriolar barrel-shaped meiotic spindle and culminates in a highly unequal division in which one set of homologues are discarded into a tiny polar body. In contrast, the first meiotic division of a primary spermatocyte takes place on a centriole-based, mitotic-like spindle, and, though cytokinesis is often incomplete, the division culminates in the symmetric division of the primary spermatocyte into two secondary spermatocytes (Ward et al. 1981) (Fig. 7 A). Unlike oocytes, in which the first meiotic division only occurs after fertilization, spermatocytes initiate their first meiotic division autonomously as soon as they mature and separate from the syncytial gonad. This first meiotic division is followed by a round of centriole duplication and the assembly of a bipolar meiosis II spindle, orthogonal to the first division axis. The separation of sister chromatids during meiosis II is accompanied by an unusual asymmetric division (spermatid budding) during which the two haploid sperm bud from a large residual cytoplast (Fig. 7 A).


Metaphase to anaphase (mat) transition-defective mutants in Caenorhabditis elegans.

Golden A, Sadler PL, Wallenfang MR, Schumacher JM, Hamill DR, Bates G, Bowerman B, Seydoux G, Shakes DC - J. Cell Biol. (2000)

Tubulin and DAPI localization in wild-type and mutant spermatocytes. Shown in A is a depiction of wild-type spermatogenesis. After nuclear envelope breakdown, the chromosomes of primary (1°) spermatocytes congress to form a meiosis I metaphase plate. The first meiotic division yields two secondary (2°) spermatocytes, which can either be separated or remain attached through a cytoplasmic connection due to incomplete cytokinesis. Secondary spermatocytes subsequently undergo a polarized budding division during which two haploid sperm separate from a central residual body. (B) A wild-type male germline squashed in the presence of Hoechst dye 33342 and observed by DIC and UV epifluorescence. All meiotic stages can be seen. Primaries (1°) and secondaries (2°) can be distinguished by size (B). A budding figure (BF) is visible in the lower right corner. Haploid sperm (S) and residual bodies (RB) are also indicated. (C) A sperm spread from a mat-3(ax82) male lacks 2° spermatocytes, but contains many anucleate sperm. Abnormal budding figures are also present in which all the chromosomes remain in the center of the developing residual body. Staining with anti–α-tubulin antibody (E, G, I, and K) and DAPI (D, F, H, and L) reveals the underlying spindle structures in these sperm spreads (E, G, I, and K). In wild-type sperm spreads, distinctive meiotic spindles are apparent in 1° and 2° spermatocytes and in budding figures (D and E). A magnified view of a wild-type meiotic spindle is shown in (I) with its corresponding DAPI image (H). In the mat mutants, normal meiosis I–like spindles form, but anaphase figures are never observed (F, G, J, and K). The diameter of a primary spermatocyte equals 12 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
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Figure 7: Tubulin and DAPI localization in wild-type and mutant spermatocytes. Shown in A is a depiction of wild-type spermatogenesis. After nuclear envelope breakdown, the chromosomes of primary (1°) spermatocytes congress to form a meiosis I metaphase plate. The first meiotic division yields two secondary (2°) spermatocytes, which can either be separated or remain attached through a cytoplasmic connection due to incomplete cytokinesis. Secondary spermatocytes subsequently undergo a polarized budding division during which two haploid sperm separate from a central residual body. (B) A wild-type male germline squashed in the presence of Hoechst dye 33342 and observed by DIC and UV epifluorescence. All meiotic stages can be seen. Primaries (1°) and secondaries (2°) can be distinguished by size (B). A budding figure (BF) is visible in the lower right corner. Haploid sperm (S) and residual bodies (RB) are also indicated. (C) A sperm spread from a mat-3(ax82) male lacks 2° spermatocytes, but contains many anucleate sperm. Abnormal budding figures are also present in which all the chromosomes remain in the center of the developing residual body. Staining with anti–α-tubulin antibody (E, G, I, and K) and DAPI (D, F, H, and L) reveals the underlying spindle structures in these sperm spreads (E, G, I, and K). In wild-type sperm spreads, distinctive meiotic spindles are apparent in 1° and 2° spermatocytes and in budding figures (D and E). A magnified view of a wild-type meiotic spindle is shown in (I) with its corresponding DAPI image (H). In the mat mutants, normal meiosis I–like spindles form, but anaphase figures are never observed (F, G, J, and K). The diameter of a primary spermatocyte equals 12 μm.
Mentions: In C. elegans, the first meiotic division of the oocyte takes place on an acentriolar barrel-shaped meiotic spindle and culminates in a highly unequal division in which one set of homologues are discarded into a tiny polar body. In contrast, the first meiotic division of a primary spermatocyte takes place on a centriole-based, mitotic-like spindle, and, though cytokinesis is often incomplete, the division culminates in the symmetric division of the primary spermatocyte into two secondary spermatocytes (Ward et al. 1981) (Fig. 7 A). Unlike oocytes, in which the first meiotic division only occurs after fertilization, spermatocytes initiate their first meiotic division autonomously as soon as they mature and separate from the syncytial gonad. This first meiotic division is followed by a round of centriole duplication and the assembly of a bipolar meiosis II spindle, orthogonal to the first division axis. The separation of sister chromatids during meiosis II is accompanied by an unusual asymmetric division (spermatid budding) during which the two haploid sperm bud from a large residual cytoplast (Fig. 7 A).

Bottom Line: Analogous mitotic defects cause M phase delays in mitotic germline proliferation.We have named this class of mutants "mat" for metaphase to anaphase transition defective.These mutants, representing six different complementation groups, all map near genes that encode subunits of the anaphase promoting complex or cyclosome, and, here, we show that one of the genes, emb-27, encodes the C. elegans CDC16 ortholog.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.

ABSTRACT
The metaphase to anaphase transition is a critical stage of the eukaryotic cell cycle, and, thus, it is highly regulated. Errors during this transition can lead to chromosome segregation defects and death of the organism. In genetic screens for temperature-sensitive maternal effect embryonic lethal (Mel) mutants, we have identified 32 mutants in the nematode Caenorhabditis elegans in which fertilized embryos arrest as one-cell embryos. In these mutant embryos, the oocyte chromosomes arrest in metaphase of meiosis I without transitioning to anaphase or producing polar bodies. An additional block in M phase exit is evidenced by the failure to form pronuclei and the persistence of phosphohistone H3 and MPM-2 antibody staining. Spermatocyte meiosis is also perturbed; primary spermatocytes arrest in metaphase of meiosis I and fail to produce secondary spermatocytes. Analogous mitotic defects cause M phase delays in mitotic germline proliferation. We have named this class of mutants "mat" for metaphase to anaphase transition defective. These mutants, representing six different complementation groups, all map near genes that encode subunits of the anaphase promoting complex or cyclosome, and, here, we show that one of the genes, emb-27, encodes the C. elegans CDC16 ortholog.

Show MeSH
Related in: MedlinePlus