The impact of developmental stage, tissue type, and sex on DNA double-strand break repair in Drosophila melanogaster.

Accurate repair of DNA double-strand breaks (DSBs) is essential for the maintenance of genome integrity, as failure to repair DSBs can result in cell death. The cell has evolved two main mechanisms for DSB repair: non-homologous end-joining (NHEJ) and homology-directed repair (HDR), which includes single-strand annealing (SSA) and homologous recombination (HR). While certain factors like age and state of the chromatin are known to influence DSB repair pathway choice, the roles of developmental stage, tissue type, and sex have yet to be elucidated in multicellular organisms. To examine the influence of these factors, DSB repair in various embryonic developmental stages, larva, and adult tissues in Drosophila melanogaster was analyzed through molecular analysis of the DR-white assay using Tracking across Indels by DEcomposition (TIDE). The proportion of HR repair was highest in tissues that maintain the canonical (G1/S/G2/M) cell cycle and suppressed in both terminally differentiated and polyploid tissues. To determine the impact of sex on repair pathway choice, repair in different tissues in both males and females was analyzed. When molecularly examining tissues containing mostly somatic cells, males and females demonstrated similar proportions of HR and NHEJ. However, when DSB repair was analyzed in male and female premeiotic germline cells utilizing phenotypic analysis of the DR-white assay, there was a significant decrease in HR in females compared to males. This study describes the impact of development, tissue-specific cycling profile, and, in some cases, sex on DSB repair outcomes, underscoring the complexity of repair in multicellular organisms.

Chromosome Preference During Homologous Recombination Repair of DNA Double-Strand Breaks in Drosophila melanogaster.

DNA double-strand breaks (DSBs) are especially toxic DNA lesions that, if left unrepaired, can lead to wide-ranging genomic instability. Of the pathways available to repair DSBs, the most accurate is homologous recombination (HR), where a homologous sequence is used as a donor template to restore genetic information at the break site. While much of the biochemical aspects of HR repair have been characterized, how the repair machinery locates and discriminates between potential homologous donor templates throughout the genome remains elusive. We use Drosophila melanogaster to investigate whether there is a preference between intrachromosomal and interhomolog donor sequences in mitotically dividing cells. Our results demonstrate that, although interhomolog HR is possible and frequent if another donor template is not available, intrachromosomal donor templates are highly preferred. This is true even if the interhomolog donor template is less diverged than the intrachromosomal donor template. Thus, despite the stringent requirements for homology, the chromosomal location of the donor template plays a more significant role in donor template choice.