Heterochromatin-Associated Proteins HP1a and Piwi Collaborate to Maintain the Association of Achiasmate Homologs in <i>Drosophila</i> Oocytes

Giauque, Christopher C.; Bickel, Sharon E.

doi:10.1534/genetics.115.186460

Cited by 16 publications

(18 citation statements)

References 71 publications

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“…Ovaries from 20 to 25 fattened females were dissected and fixed as previously described (74). Following fixation, ovaries were rinsed in 1× PBS, 0.5% BSA, 0.1% Triton X-100, transferred to a shallow dissecting dish, and late-stage egg chambers were detached from earlier stages by pipetting with a BSA-coated pipette tip.…”

Section: Fishmentioning

confidence: 99%

“…Oocytes were nutated for 2 h at room temperature in 1× PBS and 1% Triton X-100 containing 100 μg/mL RNase (ThermoFisher Scientific). In situ hybridization was performed as previously described (74). The hybridization solution contained 2.5 ng/μl of a Cy3-labeled pericentric probe (5′-Cy3-AGGGATCGTTAG-CACTCGTAAT; Integrated DNA Technologies) and Alexa 647 end-labeled fragments were prepared from six BAC clones at a final concentration of 0.31 pmol fluor/μL.…”

Section: Fishmentioning

confidence: 99%

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Oxidative stress in oocytes during midprophase induces premature loss of cohesion and chromosome segregation errors

Perkins

Das

Panzera

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

101

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In humans, errors in meiotic chromosome segregation that produce aneuploid gametes increase dramatically as women age, a phenomenon termed the "maternal age effect." During meiosis, cohesion between sister chromatids keeps recombinant homologs physically attached and premature loss of cohesion can lead to missegregation of homologs during meiosis I. A growing body of evidence suggests that meiotic cohesion deteriorates as oocytes age and contributes to the maternal age effect. One hallmark of aging cells is an increase in oxidative damage caused by reactive oxygen species (ROS). Therefore, increased oxidative damage in older oocytes may be one of the factors that leads to premature loss of cohesion and segregation errors. To test this hypothesis, we used an RNAi strategy to induce oxidative stress in Drosophila oocytes and measured the fidelity of chromosome segregation during meiosis. Knockdown of either the cytoplasmic or mitochondrial ROS scavenger superoxide dismutase (SOD) caused a significant increase in segregation errors, and heterozygosity for an smc1 deletion enhanced this phenotype. FISH analysis indicated that SOD knockdown moderately increased the percentage of oocytes with arm cohesion defects. Consistent with premature loss of arm cohesion and destabilization of chiasmata, the frequency at which recombinant homologs missegregate during meiosis I is significantly greater in SOD knockdown oocytes than in controls. Together these results provide an in vivo demonstration that oxidative stress during meiotic prophase induces chromosome segregation errors and support the model that accelerated loss of cohesion in aging human oocytes is caused, at least in part, by oxidative damage. meiosis | maternal age effect | oxidative damage | reactive oxygen species | superoxide dismutase C hromosome segregation errors during female meiosis are the leading cause of birth defects and miscarriages in humans and their incidence increases dramatically with age (1). Over 90% of Down syndrome cases are the result of an extra copy of chromosome 21 inherited from the mother (2). Although the probability of a meiotic missegregation event is relatively low during a woman's twenties, by the time she reaches her early forties, she has a one in three chance of conceiving an aneuploid fetus (3). Work in the last decade has begun to shed light on the molecular mechanisms that underlie this phenomenon known as the "maternal age effect."Proper chromosome segregation during both mitosis and meiosis requires that physical linkages between sister chromatids (cohesion) be formed, maintained, and released in a regulated manner (4, 5). Sister chromatid cohesion, mediated by the evolutionarily conserved cohesin complex, is established during DNA replication. During meiosis, in addition to holding sister chromatids together, cohesion is required to maintain the physical association of recombinant homologs and is therefore essential for proper segregation during the first as well as the second meiotic division (6-8). Normally, a crossover ...

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Section: Fishmentioning

confidence: 99%

Section: Fishmentioning

confidence: 99%

Oxidative stress in oocytes during midprophase induces premature loss of cohesion and chromosome segregation errors

Perkins

Das

Panzera

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

101

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“…Chromatin stickiness has been observed in both mitosis and meiosis, between both homologous and nonhomologous chromosomes, and between all combinations of euchromatin and heterochromatin (Rhoades 1955;Yunis and Yasmineh 1971;Stack 1975, 1976). Indeed, in Drosophila oocytes, stickiness between pairs of achiasmatic homologs substitutes for chiasmata to encourage proper segregation (Giauque and Bickel 2016). However, distinguishing between chromatin stickiness and chiasmata is often difficult because, except for a few groups of organisms (especially grasshoppers), chiasmata are not well-defined structurally (John 1976;Crolla and Polani 1989;Stack 1991).…”

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confidence: 99%

Meiotic Crossing Over in Maize Knob Heterochromatin

et al. 2017

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There is ample evidence that crossing over is suppressed in heterochromatin associated with centromeres and nucleolus organizers (NORs). This characteristic has been attributed to all heterochromatin, but the generalization may not be justified. To investigate the relationship of crossing over to heterochromatin that is not associated with centromeres or NORs, we used a combination of fluorescence in situ hybridization of the maize 180-bp knob repeat to show the locations of knob heterochromatin and fluorescent immunolocalization of MLH1 protein and AFD1 protein to show the locations of MLH1 foci on maize synaptonemal complexes (SCs, pachytene chromosomes). MLH1 foci correspond to the location of recombination nodules (RNs) that mark sites of crossing over. We found that MLH1 foci occur at similar frequencies per unit length of SC in interstitial knobs and in the 1 mm segments of SC in euchromatin immediately to either side of interstitial knobs. These results indicate not only that crossing over occurs within knob heterochromatin, but also that crossing over is not suppressed in the context of SC length in maize knobs. However, because there is more DNA per unit length of SC in knobs compared to euchromatin, crossing over is suppressed (but not eliminated) in knobs in the context of DNA length compared to adjacent euchromatin.

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“…n specifies the number of flies analyzed for each genotype and * indicates a significant difference (P # 0.0001) using Mann-Whitney-Wilcoxon test. depletion of HP1a, or its paralog Rhino in germ cells, induced defects in maintenance of pericentric associations of a pair of achiasmate X chromosomes, which resulted in elevated segregation defects (Giauque and Bickel 2016). We therefore aimed to test the functional impact of the loss of the HIM domain of P180 in this process and analyzed the pairing status of heterochromatic repeats of an achiasmate pair composed of a wildtype X and a FM7 balancer chromosome in females expressing various doses of wild-type or HIM-deleted versions of P180.…”

Section: The Him Domain Of P180 Is Not Essential For Viabilitymentioning

confidence: 99%

“…This argues that the HIM domain, which is central to the direct interaction between HP1a and the large subunit of CAF-1, is also important for the maintenance of pericentric pairing during meiotic prophase; a process relying on proper HP1a loading and function (Giauque and Bickel 2016).…”

Section: The Him Domain Of P180 Is Not Essential For Viabilitymentioning

confidence: 99%

Maintenance of Heterochromatin by the Large Subunit of the CAF-1 Replication-Coupled Histone Chaperone Requires Its Interaction with HP1a Through a Conserved Motif

et al. 2017

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In eukaryotic cells, the organization of genomic DNA into chromatin regulates many biological processes, from the control of gene expression to the regulation of chromosome segregation. The proper maintenance of this structure upon cell division is therefore of prime importance during development for the maintenance of cell identity and genome stability. The chromatin assembly factor 1 (CAF-1) is involved in the assembly of H3-H4 histone dimers on newly synthesized DNA and in the maintenance of a higher order structure, the heterochromatin, through an interaction of its large subunit with the heterochromatin protein HP1a. We identify here a conserved domain in the large subunit of the CAF-1 complex required for its interaction with HP1a in the Drosophila fruit fly. Functional analysis reveals that this domain is dispensable for viability but participates in two processes involving heterochromatin: position-effect variegation and long range chromosomal interactions during meiotic prophase. Importantly, the identification in the large subunit of CAF-1 of a domain required for its interaction with HP1 allows the separation of its functions in heterochromatinrelated processes from its function in the assembly of H3-H4 dimers onto newly synthesized DNA. KEYWORDS heterochromatin; variegation; HP1; CAF-1; Drosophila I N eukaryotic cells, the chromatin is partitioned into two cytologically and functionally distinct structures: heterochromatin and euchromatin. Heterochromatin was initially defined as the part of the genome that remains condensed during the whole cell cycle and stains intensively with DNA dyes. Heterochromatin is generally gene poor; rich in repeated sequences and transposable elements (Hoskins et al. 2007). Initially considered to correspond to "junk DNA," heterochromatin contains essential protein-coding genes whose expression depends on the neighboring heterochromatin structure (Schulze et al. 2005). It encodes essential chromosomal structures such as centromeres (Sun et al. 1997) or telomeres (Mason et al. 2008) and is required for essential chromosomal functions such as homolog pairing during meiosis (Dernburg et al. 1996;Karpen et al. 1996) . While essential for the biology of the genome, many of these structures are not directly encoded in the sequence of these regions and epigenetic mechanisms are likely required for their maintenance through generations.The chromatin assembly factor-1 (CAF-1) is a heterotrimeric complex first isolated as a histone chaperone able to deposit H3-H4 dimers onto newly synthesized DNA during replication or repair (Smith and Stillman 1989;Gaillard et al. 1996). Its large subunit interacts directly with PCNA (Shibahara and Stillman 1999;Moggs et al. 2000) and the CAF-1 complex is found in vivo at the replication foci (Krude 1995;Taddei et al. 1999). The large subunit of CAF-1 has also been associated to the maintenance of heterochromatin: it was shown to be essential for the stable inheritance of gene silencing in et al. 1997); its absence in fission yeast led ...

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Heterochromatin-Associated Proteins HP1a and Piwi Collaborate to Maintain the Association of Achiasmate Homologs in Drosophila Oocytes

Cited by 16 publications

References 71 publications

Oxidative stress in oocytes during midprophase induces premature loss of cohesion and chromosome segregation errors

Oxidative stress in oocytes during midprophase induces premature loss of cohesion and chromosome segregation errors

Meiotic Crossing Over in Maize Knob Heterochromatin

Maintenance of Heterochromatin by the Large Subunit of the CAF-1 Replication-Coupled Histone Chaperone Requires Its Interaction with HP1a Through a Conserved Motif

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