Effects of Acute and Chronic Cyclophosphamide Treatment on Meiotic Progression and the Induction of DNA Double-Strand Breaks in Rat Spermatocytes1

The production of haploid gametes by meiosis is a cornerstone of sexual reproduction and maintenance of genome integrity.Zfp38mRNA is expressed in spermatocytes, indicating that transcription factor ZFP38 has the potential to regulate transcription during meiosis. In this study, we generatedZfp38conditional knockout mice (Zfp38flox/flox,Stra8-Cre, hereafter calledZfp38cKO) and found that spermatogenesis did not progress beyond meiosis prophase I inZfp38cKO mice. Using a chromosomal spread technique, we observed thatZfp38cKO spermatocytes exhibited a failure in chromosomal synapsis observed by SYCP1/SYCP3 double staining. Progression of DNA double-strand breaks (DSB) repair is disrupted inZfp38cKO spermatocytes, as revealed by γ-H2AX, RAD51 and MLH1 staining. Furthermore, the mRNA and protein levels of DSB repair enzymes and factors that guide their loading onto sites of DSBs, such as RAD51, DMC1, RAD51, TEX15 and PALB2, were significantly reduced inZfp38cKO spermatocytes. Taken together, our data suggest that ZFP38 is critical for the chromosomal synapsis and DSB repairs partially via its regulation of DSB repair-associated protein expression during meiotic progression in mouse.

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Reactivation of chromosome signalling induces reversal of the meiotic program

10.1101/754341 ◽

2019 ◽

Author(s):

Maikel Castellano-Pozo ◽

Sarai Pacheco ◽

Georgios Sioutas ◽

Angel Luis Jaso-Tamame ◽

Marian H Dore ◽

...

Keyword(s):

Synaptonemal Complex ◽

Nuclear Organization ◽

Double Strand Breaks ◽

Chromosome Movement ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Meiotic Progression ◽

Nuclear Reorganization ◽

Transcriptional Changes ◽

Chromosome Movements

AbstractChromosome movements and programmed DNA double-strand breaks (DSBs) promote homologue pairing and initiate recombination at meiosis onset. Meiotic progression involves checkpoint-controlled termination of these events when all homologue pairs achieve synapsis and form crossover precursors. We show that termination of chromosome movement and DSB formation is reversible and is continuously implemented by the synaptonemal complex (SC), which silences chromosome signals that promote CHK-2 activity. Forced removal of the SC or different meiosis-specific cohesin complexes, which are individually required for SC stability, causes rapid CHK-2-dependent reinstallation of the DSB-formation and chromosome-movement machinery. This nuclear reorganization occurs without transcriptional changes, but requires signalling from HORMA protein HTP-1. Conversely, CHK-2 inactivation causes rapid disassembly of the DSB-formation and chromosome-movement machinery. Thus, nuclear organization is constantly controlled by the level of CHK-2 activity. Our results uncover an unexpected plasticity of the meiotic program and show how chromosome signalling integrates nuclear organization with meiotic progression.

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Repair pathway choice for double-strand breaks

Essays in Biochemistry ◽

10.1042/ebc20200007 ◽

2020 ◽

Vol 64 (5) ◽

pp. 765-777 ◽

Cited By ~ 2

Author(s):

Yixi Xu ◽

Dongyi Xu

Keyword(s):

Cell Cycle ◽

Double Strand Breaks ◽

Homologous Region ◽

Gene Repair ◽

Repair Pathway ◽

Dna Double Strand Breaks ◽

Environmental Radiation ◽

Strand Breaks ◽

Dna End Resection ◽

End Resection

Abstract Deoxyribonucleic acid (DNA) is at a constant risk of damage from endogenous substances, environmental radiation, and chemical stressors. DNA double-strand breaks (DSBs) pose a significant threat to genomic integrity and cell survival. There are two major pathways for DSB repair: nonhomologous end-joining (NHEJ) and homologous recombination (HR). The extent of DNA end resection, which determines the length of the 3′ single-stranded DNA (ssDNA) overhang, is the primary factor that determines whether repair is carried out via NHEJ or HR. NHEJ, which does not require a 3′ ssDNA tail, occurs throughout the cell cycle. 53BP1 and the cofactors PTIP or RIF1-shieldin protect the broken DNA end, inhibit long-range end resection and thus promote NHEJ. In contrast, HR mainly occurs during the S/G2 phase and requires DNA end processing to create a 3′ tail that can invade a homologous region, ensuring faithful gene repair. BRCA1 and the cofactors CtIP, EXO1, BLM/DNA2, and the MRE11–RAD50–NBS1 (MRN) complex promote DNA end resection and thus HR. DNA resection is influenced by the cell cycle, the chromatin environment, and the complexity of the DNA end break. Herein, we summarize the key factors involved in repair pathway selection for DSBs and discuss recent related publications.

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