The ATM signaling cascade promotes recombination-dependent pachytene arrest in mouse spermatocytes.
The ATM signaling cascade promotes recombination-dependent pachytene arrest in mouse spermatocytes.
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DOI：
10.1371/journal.pgen.1005017
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发表时间：
2015-03
期刊：
影响因子：
4.5
通讯作者：
Roig I
中科院分区：
文献类型：
--
作者：
Pacheco S;Marcet-Ortega M;Lange J;Jasin M;Keeney S;Roig I
在小鼠精母细胞中，大多数危及减数分裂重组或突触的突变导致在第一减数分裂前期的粗线期阶段的停滞和凋亡。两种主要机制被认为是触发逮捕：一个独立的双链断裂（DSB），启动减数分裂重组，另一个激活持久的重组中间体。重组依赖性停滞反应的机制还不清楚，因此我们试图通过检查TRIP 13缺陷的突变体来确定相关因素，TRIP 13是完成减数分裂DSB修复所需的保守AAA+ ATP酶。我们发现，精母细胞与亚型Trip 13突变（Trip 13 mod/mod）逮捕的功能特点，早期粗线在野生型，即完全突触染色体没有纳入组蛋白变体H1 t到染色质。这些细胞然后经历凋亡，可能是对停滞或对性体形成缺陷的反应。然而，另外缺乏DSB响应性激酶ATM的TRIP 13缺陷细胞进一步发展，达到H1 t阳性阶段（即，类似于野生型中的中/晚期粗线），尽管存在未修复的DSB。TRIP 13缺陷型精母细胞也进展到H1 t阳性阶段，如果ATM活性被Mre 11或Nbs 1的亚型突变或ATM效应激酶CHK 2的消除所减弱。然而，这些突变背景经历了凋亡阻滞，以进一步生精进展，最有可能是由于未能形成性体。DSB数升高Mre 11和Nbs 1亚型，但不Chk 2突变体，从而描绘了ATM依赖的负反馈回路，调节DSB数的遗传要求。研究结果表明，ATM依赖的信号传导第一次强制执行正常的粗线期持续重组中间体的反应。我们的工作支持这样的结论，即重组缺陷触发精母细胞逮捕通过途径比从遗传上不同于性体失败促进凋亡，并确认后者可以发挥作用，即使当重组依赖性逮捕是无效的。这些研究结果的影响，了解精母细胞逮捕和凋亡之间的复杂关系进行了讨论。减数分裂是产生单倍体细胞的特化细胞分裂。随着生殖细胞进入第一次减数分裂前期，整个基因组中形成程序性双链断裂（DSB）。通过同源重组修复这些DSB对于在第一次减数分裂结束时同源染色体的正确分离至关重要，因此，对于产生单倍体配子至关重要。此外，不能正确修复这些DSB可能对后代的基因组完整性产生有害影响。为了确保不能修复减数分裂DSB的减数分裂母细胞不能完成减数分裂，重组受到严格控制。然而，小鼠精母细胞减数分裂重组与减数分裂进程之间的信号通路尚不清楚。我们在这里报告的ATM信号通路，组成的MRE 11复合物，ATM和CHK 2，是负责激活的重组依赖性逮捕发生在Trip 13突变小鼠精母细胞，积累未修复的DSB在减数分裂前期。
Most mutations that compromise meiotic recombination or synapsis in mouse spermatocytes result in arrest and apoptosis at the pachytene stage of the first meiotic prophase. Two main mechanisms are thought to trigger arrest: one independent of the double-strand breaks (DSBs) that initiate meiotic recombination, and another activated by persistent recombination intermediates. Mechanisms underlying the recombination-dependent arrest response are not well understood, so we sought to identify factors involved by examining mutants deficient for TRIP13, a conserved AAA+ ATPase required for the completion of meiotic DSB repair. We find that spermatocytes with a hypomorphic Trip13 mutation (Trip13mod/mod) arrest with features characteristic of early pachynema in wild type, namely, fully synapsed chromosomes without incorporation of the histone variant H1t into chromatin. These cells then undergo apoptosis, possibly in response to the arrest or in response to a defect in sex body formation. However, TRIP13-deficient cells that additionally lack the DSB-responsive kinase ATM progress further, reaching an H1t-positive stage (i.e., similar to mid/late pachynema in wild type) despite the presence of unrepaired DSBs. TRIP13-deficient spermatocytes also progress to an H1t-positive stage if ATM activity is attenuated by hypomorphic mutations in Mre11 or Nbs1 or by elimination of the ATM-effector kinase CHK2. These mutant backgrounds nonetheless experience an apoptotic block to further spermatogenic progression, most likely caused by failure to form a sex body. DSB numbers are elevated in Mre11 and Nbs1 hypomorphs but not Chk2 mutants, thus delineating genetic requirements for the ATM-dependent negative feedback loop that regulates DSB numbers. The findings demonstrate for the first time that ATM-dependent signaling enforces the normal pachytene response to persistent recombination intermediates. Our work supports the conclusion that recombination defects trigger spermatocyte arrest via pathways than are genetically distinct from sex body failure-promoted apoptosis and confirm that the latter can function even when recombination-dependent arrest is inoperative. Implications of these findings for understanding the complex relationships between spermatocyte arrest and apoptosis are discussed. Meiosis is the specialized cell division by which haploid cells are produced. As germ cells enter the first meiotic prophase, programmed double-stranded breaks (DSBs) are formed throughout the genome. Repair of these DSBs by homologous recombination is crucial for proper segregation of homologous chromosomes at the end of the first meiotic division, and thus, for the production of haploid gametes. Moreover, failure to correctly repair these DSBs can have deleterious effects on the genomic integrity of offspring. To ensure that meiocytes that fail to repair meiotic DSBs do not complete meiosis, recombination is tightly controlled. However, the signaling pathway(s) tying meiotic recombination to meiotic progression in mouse spermatocytes is not known. We report here that the ATM-signaling pathway, composed of the MRE11 complex, ATM and CHK2, is responsible for activation of the recombination-dependent arrest that occurs in Trip13 mutant mouse spermatocytes, which accumulate unrepaired DSBs during meiotic prophase.
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影响因子：
4.5
作者：
Carballo JA;Panizza S;Serrentino ME;Johnson AL;Geymonat M;Borde V;Klein F;Cha RS
通讯作者：
Cha RS
影响因子：
4.5
作者：
Ho HC;Burgess SM
通讯作者：
Burgess SM
完成减数分裂重组而不是突触需要小鼠Pachytene检查点2（TRIP13）。
影响因子：
4.5
作者：
Li XC;Schimenti JC
通讯作者：
Schimenti JC
影响因子：
4.5
作者：
Barchi M;Roig I;Di Giacomo M;de Rooij DG;Keeney S;Jasin M
通讯作者：
Jasin M
影响因子：
64.5
作者：
Barlow, C;Hirotsune, S;WynshawBoris, A
通讯作者：
WynshawBoris, A