scholarly journals Repair of Meiotic DNA Breaks and Homolog Pairing in Mouse Meiosis Requires a Minichromosome Maintenance (MCM) Paralog

Genetics ◽  
2016 ◽  
Vol 205 (2) ◽  
pp. 529-537 ◽  
Author(s):  
Adrian J. McNairn ◽  
Vera D. Rinaldi ◽  
John C. Schimenti
Keyword(s):  
Dna Breaks ◽  
Minichromosome Maintenance ◽  
Homolog Pairing

scholarly journals Mcmdc2, a minichromosome maintenance (MCM) paralog, is required for repair of meiotic DNA breaks and homolog pairing in mouse meiosis

2016 ◽  
Author(s):  
Adrian J. McNairn ◽  
Vera D. Rinaldi ◽  
John C. Schimenti
Keyword(s):  
Dna Breaks ◽  
Minichromosome Maintenance ◽  
Primordial Follicles ◽  
Homolog Pairing ◽  
Homologous Sequences ◽  
Chromosome Synapsis ◽  
Double Stranded Dna ◽  
Blm Helicase ◽  
Strand Invasion ◽  
Deficient Mice

AbstractThe mammalian Mcm-domain containing 2 (Mcmdc2) gene encodes a protein of unknown function that is homologous to the mini-chromosome maintenance family of DNA replication licensing and helicase factors. Drosophila melanogaster contains two separate genes, the “Mei-MCMs,” that appear to have arisen from a single ancestral Mcmdc2 gene. The Mei-MCMs are involved in promoting meiotic crossovers by blocking the anti-crossover activity of BLM helicase, a function performed by MSH4 and MSH5 in metazoans. Here, we report that MCMDC2-deficient mice of both sexes are viable but sterile. Males fail to produce spermatozoa, and formation of primordial follicles is disrupted in females. Histology and immunocytological analyses of mutant testes revealed that meiosis is arrested in Prophase I, and is characterized by persistent meiotic double-stranded DNA breaks (DSBs), failure of homologous chromosome synapsis and XY body formation, and an absence of crossing over. These phenotypes essentially phenocopy those of MSH4/5 deficient meiocytes. The data indicate that MCMDC2 is essential for invasion of homologous sequences by RAD51- and DMC1-coated ssDNA filaments, or stabilization of recombination intermediates following strand invasion, both of which are needed to drive stable homolog pairing and DSB repair via recombination in mice.

Prime-editors (nickases), hRad51–Cas9 nickase fusions and dCas9 have the same problem as conventional CRISPR-Cas9 of plasmid/Cas9 integration after making a double stranded break

2019 ◽  
Author(s):  
Sandeep Chakraborty
Keyword(s):  
Cellular Response ◽  
Sequencing Data ◽  
Dna Breaks ◽  
Precise Integration ◽  
Guide Rna ◽  
Double Strand Dna Breaks ◽  
Human Therapy ◽  
P53 Activation ◽  
Programmable Nucleases

‘Prime-editing’ proposes to replace traditional programmable nucleases (CRISPR-Cas9) using a catalytically impaired Cas9 (dCas9) connected to a engineered reverse transcriptase, and a guide RNA encoding both the target site and the desired change. With just a ‘nick’ on one strand, it is hypothe- sized, the negative, uncontrollable effects arising from double-strand DNA breaks (DSBs) - translocations, complex proteins, integrations and p53 activation - will be eliminated. However, sequencing data pro- vided (Accid:PRJNA565979) reveal plasmid integration, indicating that DSBs occur. Also, looking at only 16 off-targets is inadequate to assert that Prime-editing is more precise. Integration of plasmid occurs in all three versions (PE1/2/3). Interestingly, dCas9 which is known to be toxic in E. coli and yeast, is shown to have residual endonuclease activity. This also affects studies that use dCas9, like base- editors and de/methylations systems. Previous work using hRad51–Cas9 nickases also show significant integration in on-targets, as well as off-target integration [1]. Thus, we show that cellular response to nicking involves DSBs, and subsequent plasmid/Cas9 integration. This is an unacceptable outcome for any in vivo application in human therapy.

A new DNA breaks repair pathway involving PARP3 and base excision repair proteins

2018 ◽  
Vol 482 (1) ◽  
pp. 96-100
Author(s):  
E. Belousova ◽  
◽  
M. Kutuzov ◽  
P. Ivankina ◽  
A. Ishchenko ◽  
...  
Keyword(s):  
Base Excision Repair ◽  
Excision Repair ◽  
Repair Pathway ◽  
Dna Breaks ◽  
Base Excision
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