Abstract
Maintaining genome integrity is particularly important in germ cells to ensure faithful transmission of genetic information across generations. Here we systematically describe germ cell mutagenesis in wild-type and 61 DNA repair mutants cultivated over multiple generations. ~44% of the DNA repair mutants analysed showed a >2-fold increased mutagenesis with a broad spectrum of mutational outcomes. Nucleotide excision repair deficiency led to higher base substitution rates, whereas polh-1(Polη) and rev-3(Polζ) translesion synthesis polymerase mutants resulted in 50-400 bp deletions. Signatures associated with defective homologous recombination fall into two classes: 1) brc-1/BRCA1 and rad-51/RAD51 paralog mutants showed increased mutations across all mutation classes, 2) mus-81/MUS81 and slx-1/SLX1 nuclease, and him-6/BLM, helq-1/HELQ or rtel-1/RTEL1 helicase mutants primarily accumulated structural variants. Repetitive and G-quadruplex sequence-containing loci were more frequently mutated in specific DNA repair backgrounds. Tandem duplications embedded in inverted repeats were observed in helq-1 helicase mutants, and a unique pattern of 'translocations' involving homeologous sequences occurred in rip-1 recombination mutants. atm-1/ATM checkpoint mutants harboured structural variants specifically enriched in subtelomeric regions. Interestingly, locally clustered mutagenesis was only observed for combined brc-1 and cep-1/p53 deficiency. Our study provides a global view of how different DNA repair pathways contribute to prevent germ cell mutagenesis.
Highlights
Germ cells are required to pass genetic information from one generation to the rendering the maintenance of their genetic integrity important
Genomic DNA for sequencing was isolated from starved nematode populations, each a clonal expansion from a single L4 stage hermaphrodite from the first or last propagated generation (Materials and Methods, [10,11,12]). These lines pass through a single-cell bottleneck provided by the zygote, enabling us to analyse how mutations arise in the germline (Fig 1A)
Extending on our previous study primarily focused on the effects of genotoxic agents [10], we systematically catalogued the mutational characteristics of DNA repair deficiencies across all conserved C. elegans DNA repair and damage response pathways in inbred lines propagated for up to 40 generations
Summary
Germ cells are required to pass genetic information from one generation to the rendering the maintenance of their genetic integrity important. Byproducts of oxidative phosphorylation and oxygen-dependent enzymatic processes, induce 10,000–100,000 DNA lesions per cell per day, including base modifications such as 8-oxo-dG, thymine glycol and DNA single-strand breaks [2]. 3-methyl-adenine and 3-methyl-cytosine can lead to mutation by blocking replication, and O6-methyl-guanine leads to G>A changes (for review [1]). Metabolic byproducts such as reactive aldehydes form DNA adducts that can crosslink bases from complementary DNA strands generating obstacles to replication and transcription
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
