Limits...
Mutations in the alpha-tubulin 67C gene specifically impair achiasmate segregation in Drosophila melanogaster.

Matthies HJ, Messina LG, Namba R, Greer KJ, Walker MY, Hawley RS - J. Cell Biol. (1999)

Bottom Line: Genetic studies demonstrate that these mutations also strongly and specifically decrease the fidelity of achiasmate chromosome segregation.Proper centromere orientation, chromatin elongation, and faithful segregation can all be restored by a decrease in the amount of the Nod chromokinesin.These results suggest that the accurate segregation of achiasmate chromosomes requires the proper balancing of forces acting on the chromosomes during prometaphase.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Section of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616, USA.

ABSTRACT
Drosophila melanogaster oocytes heterozygous for mutations in the alpha-tubulin 67C gene (alphatub67C) display defects in centromere positioning during prometaphase of meiosis I. The centromeres do not migrate to the poleward edges of the chromatin mass, and the chromatin fails to stretch during spindle lengthening. These results suggest that the poleward forces acting at the kinetochore are compromised in the alphatub67C mutants. Genetic studies demonstrate that these mutations also strongly and specifically decrease the fidelity of achiasmate chromosome segregation. Proper centromere orientation, chromatin elongation, and faithful segregation can all be restored by a decrease in the amount of the Nod chromokinesin. These results suggest that the accurate segregation of achiasmate chromosomes requires the proper balancing of forces acting on the chromosomes during prometaphase.

Show MeSH

Related in: MedlinePlus

Bipolar spindle assembly and failure of chromatin stretching in oocytes expressing αtub67CP40. A, Drosophila female meiotic spindles were examined by indirect immunofluorescence using antitubulin antibodies. Shown are maximum intensity projections of oocytes heterozygous for the X balancer chromosome, FM7, with either 2 copies of wild-type αtub67C genes (top row) or with one copy of wild-type αtub67C and one copy of the αtub67CP40mutant version of αtub67C (bottom row). Bar, 10 μm. B, FM7/X oocytes with the indicated genotypes were immunolabeled with both antitubulin and anticore histone antibodies and analyzed by confocal microscopy. Shown are maximum intensity projections of the chromatin masses of oocyte meiotic spindles. Chromatin masses from wild-type oocytes are shown in the top row and, in the next two rows, masses from oocytes heterozygous for the αtub67CP40mutation are shown. Chromatin masses from oocytes heterozygous for both nod and αtub67CP40 are shown in the bottom row. Bar, 4 μm. Oocytes were prepared and examined as previously described with minor modifications (Theurkauf and Hawley 1992; Matthies et al. 1996).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2168102&req=5

Figure 1: Bipolar spindle assembly and failure of chromatin stretching in oocytes expressing αtub67CP40. A, Drosophila female meiotic spindles were examined by indirect immunofluorescence using antitubulin antibodies. Shown are maximum intensity projections of oocytes heterozygous for the X balancer chromosome, FM7, with either 2 copies of wild-type αtub67C genes (top row) or with one copy of wild-type αtub67C and one copy of the αtub67CP40mutant version of αtub67C (bottom row). Bar, 10 μm. B, FM7/X oocytes with the indicated genotypes were immunolabeled with both antitubulin and anticore histone antibodies and analyzed by confocal microscopy. Shown are maximum intensity projections of the chromatin masses of oocyte meiotic spindles. Chromatin masses from wild-type oocytes are shown in the top row and, in the next two rows, masses from oocytes heterozygous for the αtub67CP40mutation are shown. Chromatin masses from oocytes heterozygous for both nod and αtub67CP40 are shown in the bottom row. Bar, 4 μm. Oocytes were prepared and examined as previously described with minor modifications (Theurkauf and Hawley 1992; Matthies et al. 1996).

Mentions: Although the spindles of FM7/X; αtub67CP40/+ oocytes are, on average, somewhat shorter than wild-type spindles (average spindle lengths are 12.2 versus 15.1 μm, respectively), confocal studies did not reveal obvious defects in spindle structure, as shown in Fig. 1 A. However, an examination of chromatin in FM7/X; αtub67CP40/+ prometaphase oocytes revealed a failure of the chromatin mass to elongate along the axis of the spindle (see Fig. 1 B; compare top two rows).


Mutations in the alpha-tubulin 67C gene specifically impair achiasmate segregation in Drosophila melanogaster.

Matthies HJ, Messina LG, Namba R, Greer KJ, Walker MY, Hawley RS - J. Cell Biol. (1999)

Bipolar spindle assembly and failure of chromatin stretching in oocytes expressing αtub67CP40. A, Drosophila female meiotic spindles were examined by indirect immunofluorescence using antitubulin antibodies. Shown are maximum intensity projections of oocytes heterozygous for the X balancer chromosome, FM7, with either 2 copies of wild-type αtub67C genes (top row) or with one copy of wild-type αtub67C and one copy of the αtub67CP40mutant version of αtub67C (bottom row). Bar, 10 μm. B, FM7/X oocytes with the indicated genotypes were immunolabeled with both antitubulin and anticore histone antibodies and analyzed by confocal microscopy. Shown are maximum intensity projections of the chromatin masses of oocyte meiotic spindles. Chromatin masses from wild-type oocytes are shown in the top row and, in the next two rows, masses from oocytes heterozygous for the αtub67CP40mutation are shown. Chromatin masses from oocytes heterozygous for both nod and αtub67CP40 are shown in the bottom row. Bar, 4 μm. Oocytes were prepared and examined as previously described with minor modifications (Theurkauf and Hawley 1992; Matthies et al. 1996).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2168102&req=5

Figure 1: Bipolar spindle assembly and failure of chromatin stretching in oocytes expressing αtub67CP40. A, Drosophila female meiotic spindles were examined by indirect immunofluorescence using antitubulin antibodies. Shown are maximum intensity projections of oocytes heterozygous for the X balancer chromosome, FM7, with either 2 copies of wild-type αtub67C genes (top row) or with one copy of wild-type αtub67C and one copy of the αtub67CP40mutant version of αtub67C (bottom row). Bar, 10 μm. B, FM7/X oocytes with the indicated genotypes were immunolabeled with both antitubulin and anticore histone antibodies and analyzed by confocal microscopy. Shown are maximum intensity projections of the chromatin masses of oocyte meiotic spindles. Chromatin masses from wild-type oocytes are shown in the top row and, in the next two rows, masses from oocytes heterozygous for the αtub67CP40mutation are shown. Chromatin masses from oocytes heterozygous for both nod and αtub67CP40 are shown in the bottom row. Bar, 4 μm. Oocytes were prepared and examined as previously described with minor modifications (Theurkauf and Hawley 1992; Matthies et al. 1996).
Mentions: Although the spindles of FM7/X; αtub67CP40/+ oocytes are, on average, somewhat shorter than wild-type spindles (average spindle lengths are 12.2 versus 15.1 μm, respectively), confocal studies did not reveal obvious defects in spindle structure, as shown in Fig. 1 A. However, an examination of chromatin in FM7/X; αtub67CP40/+ prometaphase oocytes revealed a failure of the chromatin mass to elongate along the axis of the spindle (see Fig. 1 B; compare top two rows).

Bottom Line: Genetic studies demonstrate that these mutations also strongly and specifically decrease the fidelity of achiasmate chromosome segregation.Proper centromere orientation, chromatin elongation, and faithful segregation can all be restored by a decrease in the amount of the Nod chromokinesin.These results suggest that the accurate segregation of achiasmate chromosomes requires the proper balancing of forces acting on the chromosomes during prometaphase.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Section of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616, USA.

ABSTRACT
Drosophila melanogaster oocytes heterozygous for mutations in the alpha-tubulin 67C gene (alphatub67C) display defects in centromere positioning during prometaphase of meiosis I. The centromeres do not migrate to the poleward edges of the chromatin mass, and the chromatin fails to stretch during spindle lengthening. These results suggest that the poleward forces acting at the kinetochore are compromised in the alphatub67C mutants. Genetic studies demonstrate that these mutations also strongly and specifically decrease the fidelity of achiasmate chromosome segregation. Proper centromere orientation, chromatin elongation, and faithful segregation can all be restored by a decrease in the amount of the Nod chromokinesin. These results suggest that the accurate segregation of achiasmate chromosomes requires the proper balancing of forces acting on the chromosomes during prometaphase.

Show MeSH
Related in: MedlinePlus