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ZIP4H (TEX11) deficiency in the mouse impairs meiotic double strand break repair and the regulation of crossing over.

Adelman CA, Petrini JH - PLoS Genet. (2008)

Bottom Line: As is true for hypomorphic Nbs1 (Nbs1(DeltaB/DeltaB)) mice, Zip4h(-/Y) mutant mice were fertile.Achiasmate chromosomes at the first meiotic division were also observed in Zip4h(-/Y) mutants, consistent with the observed reduction in MLH1 focus formation.These results indicate that meiotic functions of Zip4 family members are conserved and support the view that the Mre11 complex and ZIP4H interact functionally during the execution of the meiotic program in mammals.

View Article: PubMed Central - PubMed

Affiliation: Molecular Biology and Genetics Program, Sloan-Kettering Institute, New York, New York, United States of America.

ABSTRACT
We have recently shown that hypomorphic Mre11 complex mouse mutants exhibit defects in the repair of meiotic double strand breaks (DSBs). This is associated with perturbation of synaptonemal complex morphogenesis, repair and regulation of crossover formation. To further assess the Mre11 complex's role in meiotic progression, we identified testis-specific NBS1-interacting proteins via two-hybrid screening in yeast. In this screen, Zip4h (Tex11), a male germ cell specific X-linked gene was isolated. Based on sequence and predicted structural similarity to the S. cerevisiae and A. thaliana Zip4 orthologs, ZIP4H appears to be the mammalian ortholog. In S. cerevisiae and A. thaliana, Zip4 is a meiosis-specific protein that regulates the level of meiotic crossovers, thus influencing homologous chromosome segregation in these organisms. As is true for hypomorphic Nbs1 (Nbs1(DeltaB/DeltaB)) mice, Zip4h(-/Y) mutant mice were fertile. Analysis of spermatocytes revealed a delay in meiotic double strand break repair and decreased crossover formation as inferred from DMC1 and MLH1 staining patterns, respectively. Achiasmate chromosomes at the first meiotic division were also observed in Zip4h(-/Y) mutants, consistent with the observed reduction in MLH1 focus formation. These results indicate that meiotic functions of Zip4 family members are conserved and support the view that the Mre11 complex and ZIP4H interact functionally during the execution of the meiotic program in mammals.

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Zip4h−/Y mice exhibit perturbations with respect to crossover formation.Numbers of MLH1 foci per cell were tabulated in MLH1 positive spermatocyte spreads from Zip4h+/Y and Zip4−/Y mice and percent spreads containing the indicated foci were graphed (A). To determine whether DSB repair foci persisted to the stage when crossovers form, cells were co-stained with antibodies against MLH1 (red), RAD51 (green) and SCP3 (blue). Representative bivalents from Zip4h+/Y (B), and Zip4h−/Y (C) spreads are shown.
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pgen-1000042-g005: Zip4h−/Y mice exhibit perturbations with respect to crossover formation.Numbers of MLH1 foci per cell were tabulated in MLH1 positive spermatocyte spreads from Zip4h+/Y and Zip4−/Y mice and percent spreads containing the indicated foci were graphed (A). To determine whether DSB repair foci persisted to the stage when crossovers form, cells were co-stained with antibodies against MLH1 (red), RAD51 (green) and SCP3 (blue). Representative bivalents from Zip4h+/Y (B), and Zip4h−/Y (C) spreads are shown.

Mentions: To determine if ZIP4H deficiency influenced crossover formation, spermatocytes were labeled with MLH1 antibody. MLH1 is a MutL family protein required for formation of the bulk of crossovers in mice, and MLH1 foci numbers and distribution closely correlate with those of crossovers [45]–[48]. Although the small subset of crossovers formed via MLH1-independent mechanisms [4],[45],[49] are not addressed in these analyses, the number and disposition of the majority of crossovers can be assessed by MLH1 staining. A significant decrease in mean autosomal crossovers was observed, from 23.5 in controls to 21.2 in the mutants (Wilcoxan rank sum, W = 9505.5, P(two-sided) = 1.60e-11; Figure 5A). It is noteworthy that because the minimum threshold was set at 18 foci, this value likely under represents the reduction in crossovers in the mutants. Perhaps due to the transient association of MLH1 at the XY crossover, measurement of XY bivalent exchange frequencies was highly variable in both mutants and controls, and therefore inconclusive (for example, percent wildtype bivalents with 0 crossovers: autosomes = 1.25%±0.5 SD; XY = 82%±14.5). Since percentage of MLH1 positive pachytene cells was similar (35% in controls and 33% in mutants), and MLH1 positive diplotene cells were rarely observed, these results imply that recombination is reduced in the absence of ZIP4H, rather than delayed.


ZIP4H (TEX11) deficiency in the mouse impairs meiotic double strand break repair and the regulation of crossing over.

Adelman CA, Petrini JH - PLoS Genet. (2008)

Zip4h−/Y mice exhibit perturbations with respect to crossover formation.Numbers of MLH1 foci per cell were tabulated in MLH1 positive spermatocyte spreads from Zip4h+/Y and Zip4−/Y mice and percent spreads containing the indicated foci were graphed (A). To determine whether DSB repair foci persisted to the stage when crossovers form, cells were co-stained with antibodies against MLH1 (red), RAD51 (green) and SCP3 (blue). Representative bivalents from Zip4h+/Y (B), and Zip4h−/Y (C) spreads are shown.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2267488&req=5

pgen-1000042-g005: Zip4h−/Y mice exhibit perturbations with respect to crossover formation.Numbers of MLH1 foci per cell were tabulated in MLH1 positive spermatocyte spreads from Zip4h+/Y and Zip4−/Y mice and percent spreads containing the indicated foci were graphed (A). To determine whether DSB repair foci persisted to the stage when crossovers form, cells were co-stained with antibodies against MLH1 (red), RAD51 (green) and SCP3 (blue). Representative bivalents from Zip4h+/Y (B), and Zip4h−/Y (C) spreads are shown.
Mentions: To determine if ZIP4H deficiency influenced crossover formation, spermatocytes were labeled with MLH1 antibody. MLH1 is a MutL family protein required for formation of the bulk of crossovers in mice, and MLH1 foci numbers and distribution closely correlate with those of crossovers [45]–[48]. Although the small subset of crossovers formed via MLH1-independent mechanisms [4],[45],[49] are not addressed in these analyses, the number and disposition of the majority of crossovers can be assessed by MLH1 staining. A significant decrease in mean autosomal crossovers was observed, from 23.5 in controls to 21.2 in the mutants (Wilcoxan rank sum, W = 9505.5, P(two-sided) = 1.60e-11; Figure 5A). It is noteworthy that because the minimum threshold was set at 18 foci, this value likely under represents the reduction in crossovers in the mutants. Perhaps due to the transient association of MLH1 at the XY crossover, measurement of XY bivalent exchange frequencies was highly variable in both mutants and controls, and therefore inconclusive (for example, percent wildtype bivalents with 0 crossovers: autosomes = 1.25%±0.5 SD; XY = 82%±14.5). Since percentage of MLH1 positive pachytene cells was similar (35% in controls and 33% in mutants), and MLH1 positive diplotene cells were rarely observed, these results imply that recombination is reduced in the absence of ZIP4H, rather than delayed.

Bottom Line: As is true for hypomorphic Nbs1 (Nbs1(DeltaB/DeltaB)) mice, Zip4h(-/Y) mutant mice were fertile.Achiasmate chromosomes at the first meiotic division were also observed in Zip4h(-/Y) mutants, consistent with the observed reduction in MLH1 focus formation.These results indicate that meiotic functions of Zip4 family members are conserved and support the view that the Mre11 complex and ZIP4H interact functionally during the execution of the meiotic program in mammals.

View Article: PubMed Central - PubMed

Affiliation: Molecular Biology and Genetics Program, Sloan-Kettering Institute, New York, New York, United States of America.

ABSTRACT
We have recently shown that hypomorphic Mre11 complex mouse mutants exhibit defects in the repair of meiotic double strand breaks (DSBs). This is associated with perturbation of synaptonemal complex morphogenesis, repair and regulation of crossover formation. To further assess the Mre11 complex's role in meiotic progression, we identified testis-specific NBS1-interacting proteins via two-hybrid screening in yeast. In this screen, Zip4h (Tex11), a male germ cell specific X-linked gene was isolated. Based on sequence and predicted structural similarity to the S. cerevisiae and A. thaliana Zip4 orthologs, ZIP4H appears to be the mammalian ortholog. In S. cerevisiae and A. thaliana, Zip4 is a meiosis-specific protein that regulates the level of meiotic crossovers, thus influencing homologous chromosome segregation in these organisms. As is true for hypomorphic Nbs1 (Nbs1(DeltaB/DeltaB)) mice, Zip4h(-/Y) mutant mice were fertile. Analysis of spermatocytes revealed a delay in meiotic double strand break repair and decreased crossover formation as inferred from DMC1 and MLH1 staining patterns, respectively. Achiasmate chromosomes at the first meiotic division were also observed in Zip4h(-/Y) mutants, consistent with the observed reduction in MLH1 focus formation. These results indicate that meiotic functions of Zip4 family members are conserved and support the view that the Mre11 complex and ZIP4H interact functionally during the execution of the meiotic program in mammals.

Show MeSH
Related in: MedlinePlus