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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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TUNEL positive metaphase cells in testis of Zip4h−/Y mice.Testis sections from mutant and control mice were TUNEL labeled (green) and counterstained with DAPI (pseudocolored red) to assess cell death. TUNEL negative stage XII section from a wildtype mouse (A, B) containing cells with metaphase configurations (A, arrows; same image in B showing only greyscale DAPI). TUNEL positive cells from a Zip4h−/Y mouse (C, D), some exhibiting metaphase configurations (arrows). Average numbers of TUNEL positive cells per stage XII tubule are graphed with standard deviations (E).
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pgen-1000042-g008: TUNEL positive metaphase cells in testis of Zip4h−/Y mice.Testis sections from mutant and control mice were TUNEL labeled (green) and counterstained with DAPI (pseudocolored red) to assess cell death. TUNEL negative stage XII section from a wildtype mouse (A, B) containing cells with metaphase configurations (A, arrows; same image in B showing only greyscale DAPI). TUNEL positive cells from a Zip4h−/Y mouse (C, D), some exhibiting metaphase configurations (arrows). Average numbers of TUNEL positive cells per stage XII tubule are graphed with standard deviations (E).

Mentions: To determine if increased cell death was apparent in tubules in the meiotic division stage (stage XII) of the seminiferous cycle, testis sections were TUNEL stained and analyzed. The number of TUNEL positive cells in stage XII tubules increased more than two fold, from 1.2 in controls to 2.8 in Zip4h mutants (Figure 8; Wilcoxan, W = 681, P(one sided) = 0.03). These cells often had a hypercondensed metaphase-like configuration of chromatin (see Figure 8C and 8D). Although no significant difference was observed in the overall proportion of TUNEL positive cells when all tubules were analyzed, this may be explained via feedback and integration of death at this stage into the mechanisms that regulate sperm production and cell death throughout the spermatogenic cycle [58]–[60]. It is not clear whether TUNEL positive MI cells represent true apoptotic cells, however death of mitotically arrested cells has been reported previously [4],[61],[62]. This result correlates with the magnitude of the increase in diakinesis spreads containing achiasmate chromosomes, and is consistent with the lack of aneuploid MII metaphases. We propose that these observations are a result of achiasmate chromosomes triggering a spindle checkpoint [61] at MI leading to cell death.


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)

TUNEL positive metaphase cells in testis of Zip4h−/Y mice.Testis sections from mutant and control mice were TUNEL labeled (green) and counterstained with DAPI (pseudocolored red) to assess cell death. TUNEL negative stage XII section from a wildtype mouse (A, B) containing cells with metaphase configurations (A, arrows; same image in B showing only greyscale DAPI). TUNEL positive cells from a Zip4h−/Y mouse (C, D), some exhibiting metaphase configurations (arrows). Average numbers of TUNEL positive cells per stage XII tubule are graphed with standard deviations (E).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2267488&req=5

pgen-1000042-g008: TUNEL positive metaphase cells in testis of Zip4h−/Y mice.Testis sections from mutant and control mice were TUNEL labeled (green) and counterstained with DAPI (pseudocolored red) to assess cell death. TUNEL negative stage XII section from a wildtype mouse (A, B) containing cells with metaphase configurations (A, arrows; same image in B showing only greyscale DAPI). TUNEL positive cells from a Zip4h−/Y mouse (C, D), some exhibiting metaphase configurations (arrows). Average numbers of TUNEL positive cells per stage XII tubule are graphed with standard deviations (E).
Mentions: To determine if increased cell death was apparent in tubules in the meiotic division stage (stage XII) of the seminiferous cycle, testis sections were TUNEL stained and analyzed. The number of TUNEL positive cells in stage XII tubules increased more than two fold, from 1.2 in controls to 2.8 in Zip4h mutants (Figure 8; Wilcoxan, W = 681, P(one sided) = 0.03). These cells often had a hypercondensed metaphase-like configuration of chromatin (see Figure 8C and 8D). Although no significant difference was observed in the overall proportion of TUNEL positive cells when all tubules were analyzed, this may be explained via feedback and integration of death at this stage into the mechanisms that regulate sperm production and cell death throughout the spermatogenic cycle [58]–[60]. It is not clear whether TUNEL positive MI cells represent true apoptotic cells, however death of mitotically arrested cells has been reported previously [4],[61],[62]. This result correlates with the magnitude of the increase in diakinesis spreads containing achiasmate chromosomes, and is consistent with the lack of aneuploid MII metaphases. We propose that these observations are a result of achiasmate chromosomes triggering a spindle checkpoint [61] at MI leading to cell death.

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