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The inhibition of polo kinase by matrimony maintains G2 arrest in the meiotic cell cycle.

Xiang Y, Takeo S, Florens L, Hughes SE, Huo LJ, Gilliland WD, Swanson SK, Teeter K, Schwartz JW, Washburn MP, Jaspersen SL, Hawley RS - PLoS Biol. (2007)

Bottom Line: Loss-of-function mtrm mutants result in precocious NEB.The meiotic defects observed in mtrm/+ heterozygotes are fully suppressed by reducing the dose of polo+, demonstrating that Mtrm acts as an inhibitor of Polo.Our data suggest a model in which the eventual activation of Cdc25 by an excess of Polo at stage 13 triggers NEB and entry into prometaphase.

View Article: PubMed Central - PubMed

Affiliation: Stowers Institute for Medical Research, Kansas City, Missouri, United States of America.

ABSTRACT
Many meiotic systems in female animals include a lengthy arrest in G2 that separates the end of pachytene from nuclear envelope breakdown (NEB). However, the mechanisms by which a meiotic cell can arrest for long periods of time (decades in human females) have remained a mystery. The Drosophila Matrimony (Mtrm) protein is expressed from the end of pachytene until the completion of meiosis I. Loss-of-function mtrm mutants result in precocious NEB. Coimmunoprecipitation experiments reveal that Mtrm physically interacts with Polo kinase (Polo) in vivo, and multidimensional protein identification technology mass spectrometry analysis reveals that Mtrm binds to Polo with an approximate stoichiometry of 1:1. Mutation of a Polo-Box Domain (PBD) binding site in Mtrm ablates the function of Mtrm and the physical interaction of Mtrm with Polo. The meiotic defects observed in mtrm/+ heterozygotes are fully suppressed by reducing the dose of polo+, demonstrating that Mtrm acts as an inhibitor of Polo. Mtrm acts as a negative regulator of Polo during the later stages of G2 arrest. Indeed, both the repression of Polo expression until stage 11 and the inactivation of newly synthesized Polo by Mtrm until stage 13 play critical roles in maintaining and properly terminating G2 arrest. Our data suggest a model in which the eventual activation of Cdc25 by an excess of Polo at stage 13 triggers NEB and entry into prometaphase.

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Heterozygosity for mtrm126 Impairs the Proper Co-Orientation of Achiasmate Centromeres during Prometaphase(A) FISH analysis using probes homologous to the X and 4th chromosomal heterochromatin [29] were used to assay centromere co-orientation during meiotic prometaphase. In mtrm+/ mtrm+ oocytes carrying either chiasmate X chromosomes (XX females) or achiasmate X chromosomes (FM7/X females), the centromeres of both the X and the 4th are virtually always oriented toward opposite poles (see panels 1 and 4 and (B)). However, in mtrm/+ heterozygotes, the centromeres of achiasmate bivalents are often oriented towards the same pole (see panels 2 and 5 and (B)). In double heterozygotes for both mtrm and polo, these defects in achiasmate chromosome centromere co-orientation are greatly suppressed (panels 3 and 6).(B) Quantitative summary of centromere co-orientation patterns for the various genotypes studied. Although heterozygosity for mtrm126 has a dramatic effect on 4th chromosome centromere malorientation in both XX and FM7/X females, there is little effect on X chromosome segregation in XX oocytes when compared with the dramatic effect observed in FM7/X females. This is to be expected based on the genetic studies of Harris et al. [9], who observed that only achiasmate bivalents nondisjoin in mtrm/+ females.
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pbio-0050323-g008: Heterozygosity for mtrm126 Impairs the Proper Co-Orientation of Achiasmate Centromeres during Prometaphase(A) FISH analysis using probes homologous to the X and 4th chromosomal heterochromatin [29] were used to assay centromere co-orientation during meiotic prometaphase. In mtrm+/ mtrm+ oocytes carrying either chiasmate X chromosomes (XX females) or achiasmate X chromosomes (FM7/X females), the centromeres of both the X and the 4th are virtually always oriented toward opposite poles (see panels 1 and 4 and (B)). However, in mtrm/+ heterozygotes, the centromeres of achiasmate bivalents are often oriented towards the same pole (see panels 2 and 5 and (B)). In double heterozygotes for both mtrm and polo, these defects in achiasmate chromosome centromere co-orientation are greatly suppressed (panels 3 and 6).(B) Quantitative summary of centromere co-orientation patterns for the various genotypes studied. Although heterozygosity for mtrm126 has a dramatic effect on 4th chromosome centromere malorientation in both XX and FM7/X females, there is little effect on X chromosome segregation in XX oocytes when compared with the dramatic effect observed in FM7/X females. This is to be expected based on the genetic studies of Harris et al. [9], who observed that only achiasmate bivalents nondisjoin in mtrm/+ females.

Mentions: Because the karyosomes of mtrm/+ females were poorly formed before NEB and are usually transiently dissolved to individual bivalents shortly after NEB (see above), we also examined centromere co-orientation on bipolar prometaphase spindles using FISH probes (see Materials and Methods) directed against the X and 4th chromosomes (Figure 8) in both wild-type and mtrm/+ oocytes.


The inhibition of polo kinase by matrimony maintains G2 arrest in the meiotic cell cycle.

Xiang Y, Takeo S, Florens L, Hughes SE, Huo LJ, Gilliland WD, Swanson SK, Teeter K, Schwartz JW, Washburn MP, Jaspersen SL, Hawley RS - PLoS Biol. (2007)

Heterozygosity for mtrm126 Impairs the Proper Co-Orientation of Achiasmate Centromeres during Prometaphase(A) FISH analysis using probes homologous to the X and 4th chromosomal heterochromatin [29] were used to assay centromere co-orientation during meiotic prometaphase. In mtrm+/ mtrm+ oocytes carrying either chiasmate X chromosomes (XX females) or achiasmate X chromosomes (FM7/X females), the centromeres of both the X and the 4th are virtually always oriented toward opposite poles (see panels 1 and 4 and (B)). However, in mtrm/+ heterozygotes, the centromeres of achiasmate bivalents are often oriented towards the same pole (see panels 2 and 5 and (B)). In double heterozygotes for both mtrm and polo, these defects in achiasmate chromosome centromere co-orientation are greatly suppressed (panels 3 and 6).(B) Quantitative summary of centromere co-orientation patterns for the various genotypes studied. Although heterozygosity for mtrm126 has a dramatic effect on 4th chromosome centromere malorientation in both XX and FM7/X females, there is little effect on X chromosome segregation in XX oocytes when compared with the dramatic effect observed in FM7/X females. This is to be expected based on the genetic studies of Harris et al. [9], who observed that only achiasmate bivalents nondisjoin in mtrm/+ females.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2100146&req=5

pbio-0050323-g008: Heterozygosity for mtrm126 Impairs the Proper Co-Orientation of Achiasmate Centromeres during Prometaphase(A) FISH analysis using probes homologous to the X and 4th chromosomal heterochromatin [29] were used to assay centromere co-orientation during meiotic prometaphase. In mtrm+/ mtrm+ oocytes carrying either chiasmate X chromosomes (XX females) or achiasmate X chromosomes (FM7/X females), the centromeres of both the X and the 4th are virtually always oriented toward opposite poles (see panels 1 and 4 and (B)). However, in mtrm/+ heterozygotes, the centromeres of achiasmate bivalents are often oriented towards the same pole (see panels 2 and 5 and (B)). In double heterozygotes for both mtrm and polo, these defects in achiasmate chromosome centromere co-orientation are greatly suppressed (panels 3 and 6).(B) Quantitative summary of centromere co-orientation patterns for the various genotypes studied. Although heterozygosity for mtrm126 has a dramatic effect on 4th chromosome centromere malorientation in both XX and FM7/X females, there is little effect on X chromosome segregation in XX oocytes when compared with the dramatic effect observed in FM7/X females. This is to be expected based on the genetic studies of Harris et al. [9], who observed that only achiasmate bivalents nondisjoin in mtrm/+ females.
Mentions: Because the karyosomes of mtrm/+ females were poorly formed before NEB and are usually transiently dissolved to individual bivalents shortly after NEB (see above), we also examined centromere co-orientation on bipolar prometaphase spindles using FISH probes (see Materials and Methods) directed against the X and 4th chromosomes (Figure 8) in both wild-type and mtrm/+ oocytes.

Bottom Line: Loss-of-function mtrm mutants result in precocious NEB.The meiotic defects observed in mtrm/+ heterozygotes are fully suppressed by reducing the dose of polo+, demonstrating that Mtrm acts as an inhibitor of Polo.Our data suggest a model in which the eventual activation of Cdc25 by an excess of Polo at stage 13 triggers NEB and entry into prometaphase.

View Article: PubMed Central - PubMed

Affiliation: Stowers Institute for Medical Research, Kansas City, Missouri, United States of America.

ABSTRACT
Many meiotic systems in female animals include a lengthy arrest in G2 that separates the end of pachytene from nuclear envelope breakdown (NEB). However, the mechanisms by which a meiotic cell can arrest for long periods of time (decades in human females) have remained a mystery. The Drosophila Matrimony (Mtrm) protein is expressed from the end of pachytene until the completion of meiosis I. Loss-of-function mtrm mutants result in precocious NEB. Coimmunoprecipitation experiments reveal that Mtrm physically interacts with Polo kinase (Polo) in vivo, and multidimensional protein identification technology mass spectrometry analysis reveals that Mtrm binds to Polo with an approximate stoichiometry of 1:1. Mutation of a Polo-Box Domain (PBD) binding site in Mtrm ablates the function of Mtrm and the physical interaction of Mtrm with Polo. The meiotic defects observed in mtrm/+ heterozygotes are fully suppressed by reducing the dose of polo+, demonstrating that Mtrm acts as an inhibitor of Polo. Mtrm acts as a negative regulator of Polo during the later stages of G2 arrest. Indeed, both the repression of Polo expression until stage 11 and the inactivation of newly synthesized Polo by Mtrm until stage 13 play critical roles in maintaining and properly terminating G2 arrest. Our data suggest a model in which the eventual activation of Cdc25 by an excess of Polo at stage 13 triggers NEB and entry into prometaphase.

Show MeSH